ELBERT
PEETS

LIBRARY

FACULTY OF FORESTRY
UNIVERSITY OF TORONTO

PRACTICAL TREE REPAIR

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Excavating a large cavity

PRACTICAL
TREE REPAIR

THE PHYSICAL REPAIR
OF TREES— BRACING AND
THE TREATMENT OF
WOUNDS AND CAVITIES

BY

ELBERT PEETS

LIBRARY

FACULTY OF FORESTR
UNIVERSITY OF TORON

NEW YORK

ROBERT M. McBRIDE & COMPANY
1916

Copyright, 1913, by
McBRiDE, NAST & Co.

Second Printing
March, 1916

6V

Published, October, 1913

TO

MY FELLOW STUDENTS

IN THE SCHOOL OF LANDSCAPE ARCHITECTURE
AT HARVARD UNIVERSITY

INTRODUCTION

BECAUSE this book is a pioneer in its field,
and because many popular misconceptions
exist as to the nature of that field, and its relation
to others, it may be well to state at the very be-
ginning what the subject-matter is, of which the
book treats. This is not a book on forestry, be-
cause forestry deals only with large tracts of wood-
land, the reproduction of forests, and the harvest-
ing and marketing of timber. Men who con-
cern themselves with the welfare of individual
trees in towns and cities ought not to call them-
selves foresters — they are, or ought to be, ar-
boriculturists. This book deals with one division
of the science of arboriculture. It has nothing,
or but little, to say concerning the planting, fertil-
ization, pruning, or spraying of trees, all of which
are important parts of the arboriculturist's work.
It is devoted entirely to the prevention and repair
of physical injuries to the framework of the tree,
such injuries as are caused by wind and ice-storm,
the ignorance or carelessness of men, the attacks
of boring insects, and of that silent destroying
host, the rot-producing fungi.

In a general way the field that it covers is the
i

ii INTRODUCTION

work often spoken of as " tree-surgery " or " tree-
doctoring." Both of these terms have been re-
jected by most reputable arboriculturists for the
reason that they produce in people's minds an an-
thropomorphic idea of a tree which is fatal to a
correct understanding of a tree's nature and a
tree's needs. A tree is a living thing, but it is not
a human being and it is not an animal. The
reasons for operating and the methods of operat-
ing upon trees and upon men are as entirely dif-
ferent as plants and animals are different. To
say the contrary betrays ignorance of both king-
doms. There is no good reason why we should
take over a word which already has acquired a
definite meaning and apply it to quite a different
group of facts and processes. To do so is bound
to produce confusion of thought.

Although our knowledge of tree repair is now
fairly considerable, it is by no means complete.
There are a great many questions, both of princi-
ple and practise, about which keen differences of
opinion exist among experienced men. Old
methods have given way to new ones, and the
process promises to continue. The new methods
spread but slowly, and judgments as to their value
differ. Inevitably, then, some readers of this
book will find in it recommendations with which
they cannot agree. Others will detect omissions.
The writer will be extremely glad to exchange let-

INTRODUCTION iii

ters with any readers who will be so good as to
give him the benefit of their ideas and their ex-
perience in the field of tree repair.

Some readers, to whom this book is an intro-
duction to the work it describes, may at times feel
that its directions are too general, and its state-
ments too often qualified. A brief practical ex-
perience will show them the necessity for a certain
degree of generality. No two trees are alike. In
order that directions may not be misleading, they
must often leave much to the judgment of the
operator.

To increase the working value of the book, the
writer has in several instances followed the com-
mon-sense European custom of stating the names
of manufacturers and their products. He is sure
that no one will accuse him of log-rolling who has
tried to acquaint himself with the materials used
in a line of work which is so young and scattered
that it is not yet represented by a trade-journal.
He makes no pretense of having discovered or
mentioned every valuable product.

During the preparation of the book the writer
has received valuable help from many people.
Mr. M. H. Horvath of Cleveland, landscape
architect and consulting forester, and Mr. John
Boddy, city forester of Cleveland, have answered
many enquiries, and Mr. Boddy has furnished the
originals of several photographic illustrations.

iv INTRODUCTION

Dr. G. E. Stone has also furnished photographs,
and has been so good as to spend much time ex-
plaining his interesting experiments and the work
of his students at the Massachusetts Agricultural
College. Mr. A. T. Hastings, Jr., City Forester
of Jersey City, has very kindly supplied photo-
graphs. To these, and many others, the writer
gratefully acknowledges his indebtedness.

CONTENTS

CHAPTER PAGE

I A PROGRAM FOR SAVING THE TREES . . i

II THE TREE'S STRUCTURE AND MANNER OF

GROWTH 10

III WOUNDS AND THEIR TREATMENT ... 23

IV BORING INSECTS AND THEIR CONTROL . . 52
V ROT-FUNGI AND THEIR WORK .... 71

VI THE VALUE AND FUNCTION OF FILLING

TREES 86

VII THE FILLING OF CAVITIES — MATERIALS

AND TOOLS 102

VIII GENERAL METHOD OF FILLING CAVITIES . 119
IX THE VARIOUS TYPES OF CAVITIES . . .159

X THE TREATMENT OF CAVITIES WITHOUT

FILLING 177

XI BRACING 198

XII THE PREVENTION OF WOUNDS AND CAVI-
TIES 217

XIII THE TRADE OF TREE REPAIR .... 233

XIV NOTES ON THE VARIOUS SPECIES . . . 239
BIBLIOGRAPHY 263

ILLUSTRATIONS

Excavating a large cavity Frontispiece

TACINO
PACK

Decayed maple before and after excavation ... 4
The same tree reinforced with rods and wire and

filled with concrete 1 6

Wounds caused by lawnmowers 26

Wounds caused by horses gnawing the bark ... 26

Frost-crack in oak 34

Oak tree with large bark wound 44

Cross-section of maple affected by white heart-rot . 72

Cross-section of damaged oak 72

Fruiting bodies of white heart-rot fungus ... 80

A tree that is not worth filling 98

Cavity in the base of a white oak filled with concrete 114
Linden excavated and bolted, ready for filling . .134

Cavity in large red maple 156

Linden on Boston Common, treated according to the

open system 186

How an iron band constricts the tree 202

Small cavity in white oak filled with concrete . . 220
Ash tree with large cavity correctly treated with zinc 236

PRACTICAL
TREE REPAIR

PRACTICAL TREE REPAIR

CHAPTER I
A PROGRAM FOR SAVING THE TREES

THE welfare of trees is now a subject of
universal interest. Our cities are grow-
ing so big that it is not so easy as it once was to
get out into the woods, and every bit of green is
a relief from the glare of the city pavements.
Around the city, too, suburbs are reaching out
into the country, greatly increasing the value of
the land, and in even greater proportion, the value
of the trees standing on the land. The spreading
meadow oak which ten years ago shaded the farm-
er's cows and escaped his ax only because its hollow
bole gave little promise of fuel, has now become
the priceless glory of some surburban garden.
The old " maple bush " is now a well-kept park.
But the trees have not been treated with the
consideration justified by their increased value.
Their fellows have been cut away, exposing them
suddenly to wind and sun. Their roots have been

2 PRACTICAL TREE REPAIR

chopped off in digging roadways and cellars; the
soil-water level to which they have become accus-
tomed has been lowered by deep drainage pipes.
Barren soil has been piled over their roots, rob-
bing them of the air which is just as essential to
them as water. Graders, teamsters, builders, and
telephone men have treated the trees as their con-
venience suggested, tearing out their roots, bruis-
ing their bark, tying guy-wires to them and lop-
ping off their branches, as if they were the dead
and worthless things which, by the time the new
suburban home is turned over to the owner, they
too often are. Is it any wonder, then, that in
most of our suburbs half the large trees are de-
cayed and dying?

Out in the open country the conditions in the
tree world are often much the same, though for
different reasons. A good many groves, for in-
stance, are now in existence solely by virtue of the
fact that the trees in them are all decayed. I
know of several beech woods in which every tree
is hollow, for the simple reason that ten or fif-
teen years ago all the sound trees were felled
for timber. Over-pasturing wood-lots has also
ruined many beautiful groves. The cattle pre-
vent the natural forest reproduction and compact
the soil so that it dries out quickly, and the old
trees can no longer make a vigorous yearly
growth, and can no longer resist the attacks of

A PROGRAM FOR SAVING TREES 3

their mortal enemies, the bark and timber borers
and the rot-producing fungi.

It is obvious, then, that we are facing peculiar
conditions, and conditions which call for a con-
sistent line of attack. We must adopt a practical
program. Such a program calls for three lines
of procedure:

First, to see to it that our young trees are so
planted and protected and attended to, that they
may grow up to be healthy and perfect specimens.

Second, in the case of old trees which are still
sound, to see to it that they are properly nourished
and cared for, and painstakingly protected from
accident and decay.

Third, in the case of old trees which are dis-
eased and weakened, to make every effort, justi-
fied by the probabilities of success and the value
of the trees, to repair them and restore them to
health and strength.

The first and second provisions of this pro-
gram are much more important than the third.
Yet the third seems to be occupying a more prom-
inent position, at least in the public eye, than the
other two together. The reason, of course, is that
" tree surgery," with its spectacular operations,
has caught the popular attention, while those
processes which aim at warding off decay and pre-
serving health, with their less immediate results,
have not made so great a popular appeal.

4 PRACTICAL TREE REPAIR

The history of the treatment of wounds and
cavities in trees is of slight importance, but is
still of considerable interest. Although it in all
probability dates almost as far back as does the
cultivation of fruit trees, the writer has not
happened to stumble on any but the most meager
references dating from earlier than the end of the
Eighteenth Century. What might be called the
modern history of the art begins, very regrettably,
with charges and denials of quackery. Mr.
William Forsyth, for many years king's gardener
at Kensington, whose name has been immortalized
in the form Forsythia, about the year 1800 dis-
covered that a mixture of such plebeian materials
as cow-dung, lime, and wood-ashes was a sovereign
cure for wounds, and he even claimed that by its
use " holes in trees may be brought to such a
degree of soundness that no one can know the new
wood from the old." Skeptics appeared and
many open letters were hurled back and forth.
Contemporary continental books on fruit growing
described more promising dressings, and the
systems of wound treatment they laid down were
surprisingly sound in principle. An Englishman,
Wm. Pontey, in his "Forest Primer," 1805,
equals most modern writers in his grasp of basic
principles. He advocates making pruning cuts
close to the trunk, as is now universally done, and
insists that cuts must be allowed to dry before they

A PROGRAM FOR SAVING TREES 5

are painted. Holes he suggests draining and
filling with dry sand. The mouth he would plug
with wood. " The plug should be driven so as to
be level with the inner bark; as, by that means,
Nature's efforts would not be obstructed in grow-
ing over it." The " Forester's Guide," published
in Edinburgh in 1824, contains a description of the
care of wounds which proves that its author,
Robert Monteath, knew nearly as much about that
subject as we do to-day.

Skipping a few years, we find some interesting
notes in Count Des Cars' " Pruning of Forest
Trees," which was first printed in 1865 and was
translated from the French by Prof. C. S. Sargent.
Des Cars' main theses were the importance of
cutting close in removing limbs, and the value of
severe pruning in restoring old trees. But he has
something to say about cavities. As he is dealing
with trees as timber, it is only relatively small
wounds which interest him. These, he says,
should be thoroughly cleaned and painted with tar
and the opening plugged with wood.

With this start, the development of modern
methods was easy. During the early period, we
must not forget, trees were repaired mainly for
their timber value. Trees which were badly
decayed did not have sufficient value to make it
worth while bothering with them. The fact that
timber trees were being operated on also had an

6 PRACTICAL TREE REPAIR

important effect on the choice of materials for
filling. Timber trees obviously must not be filled
with anything which cannot be sawed or chopped
through. Pontey doubtless meant his dry sand
to be drained out before the log was sawed. It is
doubtful if Des Cars' method can be improved on
for timber trees. When, however, in this country,
the increase of wealth in the latter part of the last
century greatly increased the value of shade trees,
these restrictions were removed. Large holes
were filled oftener than small ones, and men
naturally began to fill up holes in trees, just as they
would fill up a hole in a wall, with the only strong
material ready at hand which could be fitted to an
irregular shape — that is, with bricks and mortar
or with concrete. Thus logically grew up the
modern system of filling with concrete, a material
which is just now being displaced, in part at least,
by asphalt.

The present condition of the " tree surgery "
business is in many respects unfortunate. In the
first place a large part of the men who practise it
in a small way have not the least idea of the
structure of trees, the nature of decay, or the cor-
rect principles of treatment. They claim that
every filling will soon be grown over, and yet they
build out their concrete fillings so far that no callus
can form over them. They paint cavities with
tar to keep out the spores of fungi (or " germs,"

A PROGRAM FOR SAVING TREES 7

as they call them) and then they drive nails into
the wood, opening up a hundred little cracks, ideal
resting places for spores. Sometimes they put
elaborate filling into one side of a tree and com-
pletely neglect an incipient bark decay on the other
side, though that decay may girdle the tree and
kill it in a few years.

The large " tree surgery " and " forestry "
companies have at least a more intelligent idea of
what they are trying to do, and most of their men
are experienced and skilled in their trade. They
have a tendency, however, to concentrate their
efforts upon the conspicuous cavities, neglecting
the smaller but not less important injuries. They
do their work at great distances from their head-
quarters, and their work does not often receive
that skilled yearly care which is essential to its
ultimate success. The most regrettable feature of
all has been that the " tree surgeons," enthusiastic
about their art, and familiar with scarcely any
other phase of arboriculture, have advised the fill-
ing of almost every diseased tree about which they
have been consulted, regardless of expense or of
the tree's " expectancy of life."

Every effort has been made to surround the
work with an air of mystery. It appears that
some mysterious inner harmony between the
doctor and his arboreal patient is a prerequisite
to successful treatment. As a result of these con-

8 PRACTICAL TREE REPAIR

ditions, laymen frequently form (as they are
intended to) an exaggerated idea of the impor-
tance of tree surgery and the certainty of its re-
sults. With their vision thus distorted they
frequently rely too completely upon the filling of
cavities, when, perhaps, the same money might
be better spent in enriching the soil and planting
young trees.

The remedy for this entire state of affairs lies
in a more widespread understanding of the aims,
methods, and limitations of cavity work in trees.
It lies in a saner estimate of the comparative
values of the various branches of arboriculture.
The remedy, in other words, is to carry out,
effectively and consistently, all three provisions of
the program which has been outlined, instead of
giving our attention mainly to the least important
of them. It means that the public, the officials of
cities and towns, landscape architects, arboricul-
turists, and the tree-men and gardeners who actu-
ally handle the tools, must cooperate in carrying
out the whole program. And more than any-
thing else, we need a greater number of — and a
greater appreciation of — well-trained, all-round
arboriculturists, men who know trees, how to plant
them and how to keep them in health and protect
them from danger throughout their lives; men
capable of giving owners of trees rational, un-
biased advice, and of seeing that it is effectively

A PROGRAM FOR SAVING TREES 9

executed. And we need skilled arboricultural
workmen in every city and town.

The purpose of this book is to help all of these
groups to do a kind of work which has to be done,
and done well, in carrying out effectively each of
the three provisions of our arboricultural pro-
gram — the prevention and treatment of wounds
and the physical repair of trees. It aims to
lay before the tree owner, or the man who is
responsible for the welfare of trees, the informa-
tion he needs for undertaking this kind of work
himself, and which he needs no less if he is to hire,
intelligently, men to do the work for him. It is
also intended to serve as a handbook for those who
now practice, or may take up, the work of tree
repair as a profession.

CHAPTER II

THE TREE'S STRUCTURE AND
MANNER OF GROWTH

THERE is no necessity, in a book of this
character, for going deeply into the in-
teresting sciences of tree morphology and tree
physiology. It is, however, quite essential that a
simple account be given of the nature of arboreal
life, and especially of those points in the tree's
structure and manner of growth which make
possible the physical repair of trees. An under-
standing of these basic principles is just as
necessary to the man who would repair trees as a
thorough knowledge of human anatomy and
physiology is necessary to a physician or a surgeon.
All three do their work by virtue of certain natural
laws, which they must know well before they can
effectively use them. And, aside from the mere
utility of such information, the effort required for
its acquirement is repaid a hundredfold by the
interest it adds to every day's work in the trees and
every walk in the woods.

The word tree, like many other common words,
is not easy to define, but it will probably be safe to

10

STRUCTURE AND GROWTH n

say that we usually understand by it a sizeable,
self-supporting, woody plant with a single stem.
Trees have a definite place in the vegetable world.
They are plants which, in order to get light and
moisture, lift their leaves higher in the air than the
average, and push their roots deeper and wider
in the soil. This is the ruling principle which has
controlled the development of trees, and which has
made them as successful as they have been in their
struggle against their plant competitors. It has
controlled almost completely their shape, struc-
ture, and manner of growth. So great is the
height to which they must attain in order to over-
top their herbaceous and shrubby rivals for light,
that so much growth cannot be produced in a single
season. The growth must be cumulative, lasting
over from one season to another, and must be
strong and elastic, so that it will support large
leaf-surfaces high up in the air. The tree must
spread out, too, as well as go up, for in that way
it can get the greatest amount of light and can
save for its own use the nutriment and moisture
in the soil below it, by preventing evaporation and
the growth of other plants. As it grows higher
and wider every year, gaining a greater and greater
advantage over its competitors, its framework
must become proportionately stronger and
stronger. In other words, its trunk and branches
must grow. The roots must spread farther and

12 PRACTICAL TREE REPAIR

grip the soil more firmly every year, so they, too,
must grow.

Now growth can take place in two ways. A
thing can expand or grow from within simultane-
ously in all its parts, as a dry sponge grows when
it is dropped in water, or it can grow by addition
to its outer surface — be built up. Some plants,
such as corn and the palms, grow in the first way;
the rest, including all the northern woody plants,
grow in the second way. The second is obviously
the better way for the development of a frame-
work combining economy with strength and easy
" grow-ability," because the light and strong tis-
sues are so firmly woven and cemented together
that expansion, or growth throughout the stem,
is practically impossible. The trunks, branches,
and roots of our trees, then, are growing each year
by the addition of a layer, completely covering
them, of new wood.

The frame of a tree not only supports the
foliage but also acts as a circulation medium be-
tween the roots and the leaves. The roots absorb
water and mineral salts from the soil, and this
crude fluid passes up to the leaves, where a small
part of the oxygen and hydrogen in the water are
combined with carbon dioxide taken from the air,
and where, by use of the energy of the sun's
light, the green " chlorophyll bodies " in the leaves
combine these simple elements into complex com-

STRUCTURE AND GROWTH 13

pounds known as carbohydrates (sugar and
starch), which, dissolved in water, make the di-
gested sap. It is this digested sap which alone
can produce growth and can furnish the living cells
with the nourishment they need while they are
growing and multiplying. Even the roots depend
for the material of their growth upon this digested
sap from the leaves, the crude fluid they absorb
from the soil being of no nutritive value.

There are thus two streams normally flowing
through the trunk. One, flowing up, is of crude
sap from the roots, and the other, flowing down,
is of digested sap from the leaves. These streams
flow through separate concentric regions in the
tree's trunk. What has already been said about
the wood of the trunk being added to from the out-
side ought to give us a hint that the region carrying
the digested, growth-producing sap, is the outer —
and such it is.

With these general principles in mind, let us
glance at a cross-section of a young oak trunk.
Three concentric rings are at once noticeable, the
dark corky bark on the outside, the heartwood in
the center, and the lighter sapwood between them.
But more important to us than any of these is a
fourth ring, a very inconspicuous, soft, moist layer
between the bark and the sapwood. This is the
cambium layer.

The cambium layer is the great fact to the man

PRACTICAL TREE REPAIR

who is doing tree repairing. If an accident occurs,
his first thought is of the cambium. If he is mak-
ing an incision or filling a cavity, one eye must be
constantly on the cambium. He must learn all its
wills and won'ts, what it does and how it does it,
what can be done to it and what can not.

Cam-
bium

Sap
wood

Heart-

Woodl

Cross section of the trunk of a tree

For the cambium is the only growing part of the
tree (besides the young leaves and the tips of twigs
and roots) and if growth is to be made the cam-
bium must make it. It is the vital, growing cam-
bium which each year lays on a thin, strong layer
of new wood over the whole surface of the frame
of the tree, which builds out a tough shield of bark
to protect itself and the wood beneath it. It is the

STRUCTURE AND GROWTH 15

cambium which heals wounds and covers over
cavities.

More specifically, the cambium is a layer of cells
lying between the wood and the bark of the tree,
which, under proper conditions of temperature and
nutriment, have the power of growth and division;
that is, of producing new cells. Most of the new
cells produced by this multiplication are deposited
either on the wood which is inside the cambium,
or on the inside surface of the bark, which is out-
side the cambium, and these cells quickly lose the
characteristics of cambium cells and become special-
ized wood or bark cells. They of course no longer
have the power of growth or division, and in that
sense all the cells in the trunk except the cambium
cells and the innermost bark cells, which in many
ways work with the cambium, are dead.

Leaving the cambium for a time, let us glance
at the other regions of the trunk. The sapwood
has for its function the conveyance of water (with
small amounts of minerals dissolved therein) from
the roots to the leaves. The sapwood (of the
roots as well as of the trunk and branches) also
acts as a storehouse in which digested food is laid
up over winter. The principal effect of the re-
moval of sapwood from the tree is that the water
supply of the leaves is cut off.

The heartwood has no physiological function,
though it may help the sapwood a little at lifting

1 6 PRACTICAL TREE REPAIR

water. The great importance of the heartwood
lies in its resilient strength as a support to the
crown of the tree. It is just as dead in the tree
as it is when it is cut up into boards and built into
a house. It can be removed from the tree by man
or by fungous decay without the least injury to the
tree, provided the strength it represents is not
needed, or can be supplied in some other way.

The bark is made up of cells produced from the
cambium or a sort of assistant cambium called the
phellogen. In rough-barked trees the bark is
added to from within in annual layers. The pres-
sure generated by this constant addition from with-
in, added to that caused by the annual increment of
the wood itself, causes the outer layers of the bark
to break in irregular fissures, and ultimately to
slough off in plates and flakes. In the smooth-
barked trees a different method is pursued. The
beech, for instance, has but very little corky bark,
most of the apparent bark being live " phloem "
tissue, which meets expansion by itself growing and
expanding, thus preventing the formation of fur-
rows in its surface. The sole purpose of the bark
is to protect the cambium and wood.

It is in the cambium, as we have seen above, that
the digested sap from the leaves circulates about
the tree and passes down into the roots. Cambium
cannot live without some of this sap, and cannot
produce thrifty growth without a plentiful supply

STRUCTURE AND GROWTH 17

of it. Insomuch as the main current of sap is
from the leaves to the roots (and in spring
from the roots to the young growing twigs, for
the sap which supplies them with the materials of
growth is mostly stored over winter in the roots),
it is obvious that cambium that lies in this circuit
will be best nourished and grow fastest, and that
patches of cambium which for any reason lie
aside from the main thoroughfares of sap circula-
tion will receive least sap and will produce the
least growth, and that patches which are com-
pletely isolated will of necessity die. These facts
govern the making of incisions and the healing of
wounds in trees.

A careful study of the healing of wounds is an
excellent preparation for making incisions, which
are only purposive wounds.

Suppose we cut a small limb from a tree, fol-
lowing the practice of good pruners by making
the cut very close to the trunk. The result will
be an oval or egg-shaped wound with the cambium
of the trunk showing near its outer edge. The
sap in the cambium tends to flow in the direction
of established paths and in the direction of
least pressure. The exposed cambium around
the edge of the cut being such an area, it will re-
ceive a large flow of sap. The unconfined cells
will multiply rapidly. As a result of this rapid
growth a fold or lip will be thrown out from the

i8

PRACTICAL TREE REPAIR

region of the cut cambium layer all around the
wound. It will press firmly against the cut sur-
face, covering and protecting it. A cross-section
of this callus will show that it is structurally like
other parts of the trunk, a layer of bark enclosing
a thin layer of cambium, beneath which is the sap-

Vertical section through a pruning wound and the first, fourth,
and seventh years subsequently, showing growth of callus

wood, though the wood of a callus is harder and
more closely woven than ordinary wood. Every
year a new layer of wood will be deposited on the
callus by the callus cambium, and before many
years the wound will be completely covered.

The callus does not, of course, actually coalesce
with the cut surface, but merely rolls over it. As
wood is added to the inner edge of the fold, the
bark which is under the lip, so to speak, is pressed
against the cut surface, and if the limb were sawed

STRUCTURE AND GROWTH 19

in two through the callus a thin layer of dead or
dormant bark would be found beneath the callus,
dividing it from the surface it has spread across.
During the healing process we will usually dis-
cover that the callus grows most rapidly at the

Normal callus growth around
oval wound

Diagram of the flow of sap
about an oval wound

sides of the wound, more slowly at the top of it,
and most slowly at the bottom. The reason for
this is indicated by the accompanying figure, which
is a diagrammatic representation of the flow of
sap through the cambium around a wound in the
trunk. The sap tends to flow in a fairly straight
line. The greatest flow is past the sides of the
wound. Less comes to the top of it, and the

20

PRACTICAL TREE REPAIR

lower edge is in a sort of back-water, where it
gets but little nourishment. In some cases, as
often on the oak, these differences are not so dis-
tinct.

The effect of the tendency of the sap to flow
in continuous vertical channels is well illustrated

by the results of the
way sap has of flowing
by an irregular bark
wound. Suppose that a
patch of bark of the
shape indicated in the
diagram is torn from a
trunk, and that the ex-
posed cambium dies.
What will happen is
obvious enough. The
tongue B (see draw-
ing) , being entirely
isolated from the flow
of sap (which, it must be remembered, is normally
downward) , will soon die back to the dotted line.
The tongue A will probably die, but that is not so
certain, for projections from the upper edge of a
wound stand a better chance of getting nourish-
ment. Calluses will of course be formed at the
sides of the wound.

On the basis of these observations, we can
formulate a general rule for the shape of incisions.

An irregular bark wound

STRUCTURE AND GROWTH 21

The ideal incision is egg-shaped or oval, with the
longer axis lengthwise of the trunk or limb in
which the incision is made. As it happens, this
is the shape of the wound usually made in cutting
off a limb close to the trunk. It is highly desir-
able that the incision be as narrow as possible, but
its height, or dimension lengthwise of the trunk
or limb, is not so important. The flow of sap is

li

Four incisions in trees, the one at the left being the most dam-
aging and slowest to heal ; the one at the right least damaging
and quickest to heal

not much more seriously interfered with by a cut
six inches wide and three feet high, than by one
of the same width only one foot high, and will
heal as quickly. In some trees, especially apples
and beeches, the bast fibers are often laid on in
gentle spirals around the trunk, indicated out-
wardly by the fissures and ridges in the bark. In
such cases the incisions should follow the direction
of the fissures.

The proper location of incisions, when choice
can be exercised, is as important as shaping them
correctly. When there is a vigorous ridge in the

22 PRACTICAL TREE REPAIR

trunk, standing out like a flexed muscle, connect-
ing a large limb with a principal root, it is obvi-
ously undesirable to cut across it. Removing the
cambium would rob the root of its due supply
of digested sap, and removing the sapwood would
cut off the water supply of the limb above it. In
the same way, a wide incision should not be made
just above a thrifty root, nor just below a large
limb. In case a series of holes must be cut into
a tree in order to remove decay, it is probably
best to cut one directly above another, or, if the
tree is twisted, in a spiral. By that arrangement
there is a minimum of interference with the flow
of sap. There is considerable likelihood, how-
ever, that the bark between the incisions will die,
in which case it should be cleaned away, and the
exposed wood should be painted.

CHAPTER III
WOUNDS AND THEIR TREATMENT

WOUNDS are perhaps the most frequent pri-
mary cause of the decay and death of
trees. The vast majority of the destructive rot-
producing fungi can make their entrance into the
framework of the tree only through wounds. We
shall discuss these decays at greater length in an-
other chapter, but it is essential that, at the very
outset of our study of practical tree repair, we
clearly understand the danger which lies in
wounds. By wounds I mean all exposed surfaces
of wood, all interruptions in the normal bark
covering. Wounds are not simply esthetically
displeasing, marring, for instance, the fine texture
of the bark, nor do they merely interfere more or
less seriously with the physiological processes of
the tree. Wounds are breaches in the tree's
great wall of defense, its bark, laying the precious
treasures of its wood open to the unresisted attack
of its thousand omnipresent enemies. If you
come upon the brown shelf-like fruiting bodies
of certain rot fungi in the woods on a bright day
in fall, you will see coming from their lower sur-

23

24 PRACTICAL TREE REPAIR

faces little clouds of brown dust. Each particle
of this fine dust is a spore which has the power to
grow and cause decay and to reproduce the mother
plant. How certain it is, then, that every wound
in a tree will sooner or later become infected by
some tree disease, and that every wounded tree
is a tree in danger.

There are two general purposes or principles
which govern the treatment of wounds. We
must handle wounds in such a way as, first, to pre-
vent the entrance of decay and of insects, and,
second, to facilitate their healing. The first pur-
pose is of more immediate importance, on account
of the slowness of the healing process, which often
cannot take place at all if decay precedes it. The
second is, however, of great ultimate importance,
because healing entirely obviates the danger of in-
fection and helps the tree physiologically and
physically.

The materials used in disinfecting and treating
wounds will be considered first, and then the dif-
ferent kinds of wounds trees receive most often,
and the way each kind must be handled.

To keep insects and fungi from entering
through them, wounds must be covered with some
kind of protective dressing. Many different ma-
terials have been used for this purpose. Just at
present the matter of wound dressings is coming
to be a subject of careful investigation by arbori-

TREATMENT OF WOUNDS 25

culturists. There is a strong tendency to ques-
tion the value of materials which have long been
accepted as effective. Take paint and tar, for
instance. Men who have much to do with shade
and orchard trees are constantly coming upon old
wounds, apparently painted or tarred with care
when they were made, which are now dotted with
the exit holes of borers, and netted with season
checks. The wood at the surface of the wound
may seem substantially sound, but a blow with an
ax discloses the decayed and crumbling wood
within. In spite of these facts the general teach-
ing has been that nothing more is needed, in treat-
ing a wound, than a dressing of paint or tar. The
permanence of the dressing on the surface, even
after the decay has slipped by it into the tree, has
retarded the discovery of the actual ineffectiveness
of paint and tar.

It may be answered to this that paint and tar
are not at fault, but rather the way in which they
are used. That is in large part true. A wound-
dressing, even the best, is not a charm, and must
be carefully applied and renewed if it is to be
permanently effective. It is also true that there
are many kinds of paint and of tar. It is no less
the purpose of this discussion to point out the
right use of the old materials than it is to describe
the new ones. The man who can knock out the
general idea that a wound is dressed mainly for

26 PRACTICAL TREE REPAIR

the sake of appearances, as people are, will do
more good than the inventor of an improved
preparation.

Any discussion of dressings for wounds must
be prefaced by a determination of the things the
dressing is to be called on to do and of the in-
fluences which tend to prevent the proper dis-
charge of its functions.

The dressing is put on the wound in order to
prevent weather, insects, and fungi from getting
at the exposed wood. The weather does but little
harm per se, but it is the invariable advance agent
of fungi. To be good, a dressing must cover the
wound completely, bridging such small cracks as
there may be in it, must take tenacious hold on
the wood, weather well, and not crack or separate
from the wood. It must, in addition, be fairly
easy to apply, and must if possible be cheap.

That it is hard to find a satisfactory dressing is
largely due to the kind of surface to which it is
applied. Because the surface to which it is ap-
plied is usually moist it is hard to make the dress-
ing adhere, and because the surface is sure to check
it is hard to get a permanent covering. Painting
a wound in a tree is absolutely unlike painting a
piece of seasoned timber. It is sometimes sug-
gested that the dressing ought to prevent evapora-
tion and the checking of the wood, but in practice
it has been found that no dressing will prevent the

B

• I

TREATMENT OF WOUNDS 27

checking of fresh-cut wood. The wisest thing to
do is not to try to put on a permanent dressing
until the first checking has taken place. A heavy
dressing will then retard further checking and may
not be fractured by such checking as does occur.

The various materials which have some value
as applications to wounds can be divided into two
groups: those which sterilize the wound and cause
the death, through their fungicidal properties, of
such spores as fall on the wound while the ma-
terials persist, and those materials which fill and
cover the wood, permanently preventing the access
of spores to it. Some of these last have inci-
dental antiseptic qualities.

To the former class belong all sprays used
against fungous diseases, such as solutions of
copper sulphate and the lime-sulphur wash.
Whenever trees are sprayed with a fungicide the
nozzle should be held for an instant against each
wound, and the trunk should be sprayed as care-
fully as the bearing wood. The copper solution
is made by dissolving an ounce of copper sulphate
in a gallon of water. Other antiseptics of value
in dressing wounds are corrosive sublimate, dis-
solved in water at the rate of two ounces to fifteen
gallons, and formalin, one ounce to two gallons.

The antiseptic materials used in wood preser-
vation are also of value in treating wounds.
Foremost among them are coal tar creosote and

28 PRACTICAL TREE REPAIR

carbolineum, which is also a coal tar product,
distilled off at a higher temperature. Creosote
comes in several consistencies, the heaviest of them
requiring heating. A so-called creosote is made
from the tar which is a by-product of the manu-
facture of water-gas from petroleum, but it has no
antiseptic value. In buying creosote demand a
guarantee that it is distilled from coal tar. Two
safe brands, besides carbolineum, are the " Let-
teney " wood preservative, sold by the Northeast-
ern Company of Boston, and the " C. & A." creo-
sote. Carbolineum has been the center of much
controversy. Some observers claim it never hurts
the bark or living tissue of the trunk, while others
can prove that trees have been killed by it. Until
it is determined under what conditions it is safe,
the manufacturers warn against the application of
carbolineum to the bark or to the sapwood close
to the bark. To large surfaces it can of course
be applied without danger, and for such purposes
it has great value, as it penetrates very deep, espe-
cially if it is heated.

Creosote and carbolineum, both of which, by the
way, are commonly carried by paint dealers and
cost from sixty-five cents to a dollar or so a gallon,
do not actually fill the wood in the sense that
paints do, but they make the wood impervious to
water and immune from the attacks of insects.
The reason why they cannot be considered as com-

TREATMENT OF WOUNDS 29

plete dressings is that they do not to any extent
prevent the checking of the wood, even when they
are frequently renewed. They cannot in any way
fill or bridge over cracks. Checking continues,
though slowly, for an indefinite period. Ulti-
mately, the cracks get so large, if they are not
covered over, that water gets into them and, freez-
ing, tends to break out bits of the wood, thus ex-
posing the unimpregnated inner regions. For
this reason chemical preservatives, as distin-
guished from dressings which produce a mechani-
cal covering, have not proved successful perma-
nent applications for wounds.

Of these materials which do actually fill and
cover the wood, paint is probably the most used.
Pure white lead and linseed paint makes a very
good dressing for moderately small wounds, espe-
cially if the wood is dry when the paint is applied.
Its effectiveness is much increased if a second ap-
plication is made after the first checking has taken
place. Paint seems especially suitable for ordi-
nary orchard practice, where the wounds are not
large or inaccessible and healing is fairly rapid.
It would not do to ignore Prof. Bailey's judgment
in such a matter. " My conclusion is," he says,
" after having had the question in mind for a
decade, that a heavy application of lead paint is
the best all-round dressing for common pruning
wounds." The tree repairer, however, has often

30 PRACTICAL TREE REPAIR

to deal with quite different affairs from ordinary
pruning wounds. Suppose a large wound is
painted. In a year or two season checks form in
the wood and the inelastic paint fractures. Bor-
ing insects find little crevices in which to deposit
their eggs. The larvae burrow back and forth in
the wood, returning as adults to the wound to
emerge. At the surface the paint may stop them
temporarily, but the strong jaws of the insects
soon break it down. Each hole thus left, with a
moist mass of sawdust extending back into the
wood, is an ideal germinating bed for fungus
spores. In four or five years more the wood is
quite rotten, large cracks appear in its surface,
ants and other insects have free access. Soon the
wound is beyond any cure but a more or less ex-
pensive cavity treatment. Repeated observation
of this process has lead the writer to conclude that
a single coat of paint is a positively dangerous
dressing for large wounds, concealing, as it does,
the disintegration which goes on underneath it
almost as rapidly as if the wound had not been
dressed at all.

A very permanent dressing is the plastic ce-
ment used by slaters. It is applied in a thick
layer with a spatula. It does not become hard
nor crack if it is properly made. It has no anti-
septic quality and must be preceded by an applica-
tion of carbolineum. It is probable that the use

TREATMENT OF WOUNDS 31

of slaters' cement will become more common as
the method of making two applications, one for
sterilization and one for protection, is more widely
adopted. Dr. G. E. Stone tells me he has had
good success with the brand manufactured by the
W. F. Webster Cement Company of Cambridge,
Mass. Slaters' cement has the advantage of be-
ing very inexpensive.

Grafting wax is too expensive and adheres too
imperfectly to entitle it to a place as a regular
dressing, but the liquid form has important special
uses. It is the best thing to apply to fresh
wounds, because it does not in the least injure the
cambium. The wax can be made at home accord-
ing to the recipes to be found in Bailey's " Horti-
culturalist's Rule-Book," or it can be bought, cost-
ing about forty cents a pound. To make liquid
wax of the ordinary kind, heat it and mix about
half its weight of alcohol with it. It may be well
to give Bailey's recipe for " Lefort's liquid graft-
ing wax." u Best white resin, one pound; beef
tallow, one ounce; remove from the fire and add
eight ounces of alcohol. Keep in closed bottles
or cans."

Next to paint, tar has been the material most
commonly used as a dressing for wounds. There
are several different kinds of tar. To dispose
first of the undesirable ones, the material known
as " coal tar paint " is merely a solution of some

32 PRACTICAL TREE REPAIR

kind of asphaltum in benzine and has no value
as a wound dressing. It does not spread thickly,
dries brittle, and is rapidly dissolved by water.
Pine tar, or pitch, is rather expensive, not very
convenient to handle, and in no way superior to
coal tar. A special warning should be sounded
against those forms of tar which are hard and
brittle at ordinary temperatures and have to be
melted to be applied. Such are sure to chip off
and be unsatisfactory.

Coal tar is the material intended wherever the
word tar is used in this book. It is one of the
residuums from the distillation of bituminous coal
in the process of making coal gas. Coal tar is
sometimes called gas tar, but that expression ap-
plies also to a by-product of the manufacture of
water-gas out of petroleum. That sort of tar
has no preservative value and should not be used
on trees. In buying tar for that purpose the only
safe way is to get it from, or trace it from, a gas
works producing gas from coal. In case of doubt
have the dealer sign a guarantee that the tar is
wholly the product of the destructive distillation
of bituminous coal.

Tar makes a very good dressing if it is carefully
applied and if not too much is asked of it. It is
at its best when heavy applications are made in
winter, when it usually needs to be heated, to dry
and not too large surfaces. It is absorbed by a

TREATMENT OF WOUNDS 33

transverse cut and is then to a certain extent sub-
ject to the drawbacks attendant on the use of such
materials as creosote. It does not adhere well to
moist surfaces, blistering up easily. On large
wounds it must be frequently renewed. For in-
stance, the writer once had to treat a large bark
wound in an ironwood tree. The exposed wood
was dry and sound, though rather deeply cracked.
He applied at intervals of a week or two, during
the summer, four thorough coats of tar. The
conditions were ideal for a perfect job. Four
years later there were numerous holes through the
tar where insects had escaped and there were even
cracks through which the wood was visible. This
does not prove that tar is not a valuable dressing.
It only shows that in this case four years was too
long to wait before renewing the protective cover-
ing. That is the great point about the use of tar.
It must be renewed at frequent intervals. How
long those intervals can be depends upon circum-
stances. If a thorough second coat is given
rapidly-healing pruning wounds up to say six
inches in diameter, a year after the first coat, they
can usually be left to heal without further atten-
tion. Larger wounds should receive a second
coat the year after the first one and every second
year thereafter, until checking absolutely ceases
and a heavy impervious layer of tar is formed
over the whole surface.

34 PRACTICAL TREE REPAIR

For the little odds and ends — petty injuries
and quickly-healing wounds — a thorough daub
of tar is quite sufficient. But the strong color and
staining quality of tar must not be permitted to
lead to careless work with it. It must be flowed
on with a full brush, and every particle of the sur-
face must be covered.

Observation of the poor results obtained from
the use of paint and tar, in the way they have been
used, has naturally brought about a search for
better materials. A number of " pruning paints "
have been put on the market and many others are
being tried on a small scale. The Ohio Experi-
ment Station has undertaken a systematic study of
the various dressings. These experiments are
hardly likely to result in the discovery of a better
material than good coal tar, properly applied and
renewed. But, as a matter of fact, tar dressings
are not properly renewed, and these efforts to dis-
cover a material which does not require frequent
renewals are thoroughly justified. They have,
indeed, already given us several dressings which
are superior to tar in this important respect.

The new materials are mostly forms of asphalt.
Asphalt is a fairly pure solid bitumen resulting
from the natural or artificial distillation of petrol-
eum which, like western petroleum, has an asphalt
base, as contrasted with those forms, such as our
eastern petroleum, which have a paraffine base.

Frost crack in an oak on the grounds
of the Harvard Observatory

TREATMENT OF WOUNDS 35

Natural asphalt comes largely from Trinidad and
Venezuela. Artificial or residual asphalts are dis-
tilled by several firms, notably Byerly & Son, of
Cleveland, who call their product " Byerlite."
The Barber Asphalt Company markets natural
asphalt in many forms. The most generally use-
ful solid form is their bituminous cement No. 143.
The writer prefers it to the artificial forms. Both
cost thirty dollars a ton. The solid forms of as-
phalt can be used just as they come, being melted
for use. There are serious difficulties, however,
about applying hot preparations to tree wounds,
particularly if the wounds are high up in a tree.
Most forms which need melting, also, dry too
brittle to be perfectly effective. To avoid these
drawbacks, the asphalt is usually fluxed with some
liquid in which it will dissolve, just enough of the
solvent being used to bring the mixture to the
proper consistency. Many substances are used
for this purpose, including gasoline, petroleum
oils of various consistencies, linseed oil, and other
vegetable paint oils.

The mixture can be bought ready made or can
be made by the user. The most available com-
mercial products are various water-proofing com-
pounds, used in laying water-tables in masonry
work. The heaviest of these materials should be
chosen, and those should be avoided which are
fluxed with gasoline or benzine, for the resultant

36 PRACTICAL TREE REPAIR

coating is brittle and soluble. There are a num-
ber of compounds of asphalt made especially as
tree dressings. The one with which I have most
acquaintance is " Hoyt's Tree Varnish," a solu-
tion of asphalt in a permanent compound paint
oil. It is an extremely good preparation, being
thick, tough, and elastic. It has the drawback,
though, of costing about a dollar a gallon. The
same dealer (C. H. Hoyt, of Cleveland) puts up
a water-p roofer which he will mix especially for
tree work, such as painting cavities, and sell at
about forty cents a gallon. A number of pruning
paints are advertised in the gardening magazines.

These asphalt preparations are, in general, not
difficult to make. Simply melt the asphalt, take
the vessel containing it a short distance away from
the fire, and stir in the proper amount of the
fluxing oil. Highly inflammable gases are pro-
duced during the mixing, especially if a mineral
oil is used, and that is the reason for getting away
from the fire.

Practically any form of asphalt can be used in
making these preparations. The writer has
found the Barber cement he has mentioned in
many ways the most satisfactory, though the arti-
ficial asphalts give very good results. Further
experiments may fix on some one form of asphalt
as the best.

As a solvent, there is little reason for choosing

TREATMENT OF WOUNDS 37

the expensive paint oils over the cheap mineral
oils. Linseed oil does not result in so permanent
a dressing as does mineral oil. At the suggestion
of Mr. John Boddy, City Forester of Cleveland,
the Standard Oil Company has put on the market
a special asphalt solvent, under the name " Varno-
lene." It costs about eighteen cents a gallon at
Cleveland.

It is not easy to give definite directions as to
the proportions to be used of solvent to asphalt.
That depends on the melting point of the asphalt,
the nature of the solvent, and the season. It is
always wise to mix up small trial batches and let
them cool to air temperature, in order to deter-
mine the proportion which is right for the existing
conditions. The mixture as applied should be
rather like a soft jelly than a paint, being just as
heavy as it can be brushed on. If " Varnolene "
is used the right amount of oil for each pound of
asphalt will usually fall between a pint and a pint
and a half.

Effective as a thorough coat of asphalt paint
is, cases frequently arise which call for something
even more strong and enduring. The wound
may be a very large one, for instance, and difficult
of access, so that little dependence can be put upon
future renewals of the dressing. If it is an old
wound there are probably borers beneath the sur-
face which may be able to break through even a

3 8 PRACTICAL TREE REPAIR

heavy coat of asphalt. To meet such a situation
we have always the possibility of covering the
wound with zinc or copper. There is a method,
though, which secures quite as effective a covering
as does zinc, with less expense and less work.
That method is the reinforcement of ordinary
brushed dressings.

A dressing is reinforced by applying a fabric
to the wound and saturating the fabric with the
dressing. The materials available for this pur-
pose are numerous, such as cotton batting, burlap,
cheesecloth, and canvas. By all means the most
satisfactory, though, is cotton padding, a material
used in dressmaking. It is a thin bat of cotton,
perhaps an eighth of an inch thick. All depart-
ment stores sell it, the price being about five cents
a square yard.

Three steps must be observed in applying the
reinforced dressing. First give the wound a
thorough coat of the dressing. It is well to let
this dry a day or two. Then press the padding
against the wound and saturate it thoroughly with
the dressing. At this point the padding which ex-
tends beyond the edges of the wound can be
trimmed off. It takes only a moment to trim the
edges if a sharp instrument is used. The writer
uses old safety razor blades. When this saturat-
ing coat has dried a few days the upper surface of
the cotton padding will usually be somewhat ex-

TREATMENT OF WOUNDS 39

posed. A final surface dressing is necessary in
order to protect the cotton from the weather.
When the job is done the presence of the cotton
is barely discoverable.

Not all dressings fit this process. Tar is apt
to harden at the edges and separate from the
wood. Paint would do fairly well, though it
would be very expensive. The asphalt com-
pounds work best. The first coat on the wound
can be of tar, asphalt being used to saturate the
fabric and for the final dressing.

The manufacturers of pruning paints often ad-
vertise that their preparations contain nothing
which could be harmful to the tree. The writer
does not consider that an important point. None
of the materials commonly used is seriously in-
jurious to the wood. Tar usually kills back the
cambium an eighth or a quarter of an inch, but it
is normally killed as far back as that by drying.
Carbolineum often kills the cambium a little
farther, but is innocuous if it is kept an inch or
so from the edge of the wound. Don't choose
an expensive material over a cheap one for -the
sole reason that its analysis indicates that it con-
tains nothing which could possibly injure the cam-
bium. The cheap one may in practice be just as
good.

All this discussion of wound dressings has been
necessary in order to make intelligible the brief

40 PRACTICAL TREE REPAIR

and definite general rules for the treatment of
wounds which can now be laid down.

Prune and make incisions, whenever possible,
in late summer, fall, and early winter. Small
wounds on fast-growing wood dress with paint
or tar. If in a year they show season checks give
them a second coat. Moist wounds saturate with
a non-filling disinfectant. After checking has
taken place and the wound is dry, put on a
thorough coat of a heavy dressing. Large
wounds, in which the exposed wood is seasoned,
paint with creosote, then cover with a heavy pro-
tective dressing. If necessary, reinforce the
dressing, or cover the wound with metal. It is
extremely desirable that all wounds be inspected
yearly, and that all injuries to the coverings be
repaired promptly.

We come now to the different kinds of wounds
trees receive, and the way to treat each of them.

Trees receive mechanical injuries in a thousand
different ways. It would be impossible to enum-
erate them, nor is it necessary, for the measures
of prevention and repair are much the same. It
will be necessary only to pick out a number of
typical injuries and describe the correct treatment
of each.

The commonest kind of mechanical injury to
the trunks of trees is the bark wound. Animals
gnaw at the trees, vehicles run against them,

TREATMENT OF WOUNDS 41

gardeners bark them with lawnmowers, falling
trees crush against them, farmers use them for
fence-posts, carpenters drive nails into them,
lovers cut hearts
on them, and small
boys try their little
hatchets on their
tender bark. For
every kind of bark
wound, no matter
what its cause, the
prescription is :
" Clean up, disin-
fect, and seal."
Yet even here cir-
cumstances alter
cases, and the way
the prescription is
carried out must
be adapted to the
special cases. The
differences depend
mostly upon the length of time intervening be-
tween the making of the injury, and its treatment.
It is extremely desirable that wounds be treated
immediately after they occur. This is not, as
might be inferred from the analogy of wounds in
animals, to prevent infection, for infection takes
place rather slowly, as a rule. Promptness is

Bark wound in which almost all of
the cambium has been saved by
prompt treatment

42 PRACTICAL TREE REPAIR

desirable because by immediate attention the size
of the wound can often be greatly diminished,
and its healing can be correspondingly facilitated.
This is by virtue of the fact that when bark is torn
from a tree it is the mucilaginous cambium layer
which lets go. Some of the cambium cells come
off with the bark and some remain on the surface
of the wood. If a sufficient number remain on
the wood, and if they do not dry out, they have
the power of growing and of developing new bark-
producing cells, which rapidly replace the detached
bark. It is obviously desirable to take advantage
of this recuperative power of the cambium.
When a tree is barked the wound must be pro-
tected from the sun and wind without a moment's
delay, by replacing the torn bark or otherwise
covering it. A dressing for the wound must next
be secured. For fresh wounds nothing is better
than soft or liquid grafting wax. A mixture of
clay and cow-dung is the second choice, with
shellac and paint to choose from if neither of the
preceding materials is at hand. Tar should not
be used, as it frequently kills the cambium it is
supposed to protect.

In preparing the wound for the dressing all
detached bark must be cut away with a sharp
knife, care being taken to cut into the wood as
little as possible. The dressing should be flowed
on with a soft brush, or smeared on in such a way

TREATMENT OF WOUNDS 43

as to disturb the moist surface of the wood as little
as possible. In two or three weeks it will be easy
to see whether the operation has been successful.
The surface will have grown outward perhaps an
eighth of an inch, and scratching will disclose a
pulpy greenish layer spread over it. It will not
of course be present where the wood itself has
been scraped or bruised. The cambium can be
saved in this way with most uniform success in the
growing season.

If the bark wound has not been attended to at
once it should first be inspected to see whether any
part of the cambium has escaped drying out and
has started growing a new bark. Such areas should
of course be preserved, unless they are detached
tongues of the kind which has been described as
being too remote from the line of sap flow. In
that case they had better be removed, for they
retard healing more than they help it. The first
thing to do with an old bark wound is to clean
it up thoroughly. Clear away all dead and
shredded bark. Sound the exposed wood with a
chisel or by boring into it, if necessary. If the
wood is much decayed it may have to be filled in
one of the ways to be described in a later chapter.
A depth of decay of only an inch or two, however,
or perhaps three or four inches, if it is a large
wound, needs only to be cleared entirely away.
If the resulting excavation extends under the

44 PRACTICAL TREE REPAIR

sound callus at any point, the callus must be cut
back correspondingly or the hole must be filled.
However, a healthy callus will bridge or fill up
quite a deep wound, provided it be so thoroughly
painted or tarred that no decay or boring insects
can get at the wood.

In the case of very large bark wounds, where,
perhaps, the wood is checked and here and there
invaded by borers, and it is evident that the tree
cannot heal over the wound in many years, it
should either receive repeated coats of a very
heavy dressing, reinforced, perhaps, with cotton
padding, or it should be covered with zinc. If
the last course is decided on, after the wound is
cleaned and trimmed up the zinc is cut to fit it, a
paper pattern usually being made first. The zinc
should preferably come up rather close to the edge
of the wound, but should in no case overlap in the
least the cambium or the bark. Having the zinc
ready, paint the wound thoroughly, the back of
the zinc likewise, and nail the zinc in place with
shingle nails an inch or two apart. Its outer sur-
face must then be painted, an especially heavy
coat being flowed over the edges to make sure
that they are water-tight. Thin sheet copper
also does very well for this kind of work. The
use of sheet metal will be described more fully in
a later chapter.

A slightly different class of wounds is caused

Oak tree with large bark wound. The decayed bark

has heen cleared away and the sound wood has been

creosoted and tarred

TREATMENT OF WOUNDS 45

by the tree's growing against objects which do not
give way before it, with the result that the bark
is killed locally, or at least fails to make any
growth. Such wounds are made by the plank
seats which are frequently seen pried in between
two trees. Both trees are sure to be injured
sooner or later if the plank is not taken out every
few years and cut down a little. In such cases if
the compressed bark is dead it must be removed.
If not, it should be cleaned off, so as to be free to
grow. The tree which has had wires wound
around it, or at least stapled to one side, is another
frequent patient of the arboriculturist. The dan-
ger in such cases is that the wire will girdle or
partially girdle the tree. All wire must be pulled
out if the bark has not actually closed and joined
over it. Of similar character is the tree which
has outgrown its wire guard. If parts of the
guard have become imbedded in the trunk, they
need not be removed if such a course would re-
quire cutting the calluses closing over them. The
bark of the meeting calluses should be pared down
and perhaps slit in places, to encourage their
growth. If the tree is vigorous and the calluses
are scraped occasionally, they will ultimately grow
together organically and permit the free flow of
the sap down the cambium.

Another kind of bark wound is caused by the
rubbing together of two limbs. Something more

46 PRACTICAL TREE REPAIR

than mere local treatment is required in such cases.
The best way is to cut off one of the limbs. If
that cannot be done they must be braced apart
in one of the ways suggested in the chapter on
bracing. In addition, the worn places require
thorough wound treatment.

The breaking off of branches is another fre-
quent cause of wounds. When proper pruning
and bracing have been neglected, large limbs of
red and silver maples, linden, and such soft-
wooded trees, are often fairly torn out by the
roots. The thing to do in such a case is to clear
away completely all splintered wood and torn
bark. The essential thing is to prevent the pos-
sibility of any cracks remaining in which water can
stand and decay begin. The smoothed surface
must receive an especially heavy dressing. If it
is large and at all cracked it had better be covered
with sheet metal.

This last type of injury comes, so to speak, in
all sizes, up to the huge wounds one so often sees,
made by the tearing apart of a forked maple or
elm. These are very serious affairs and require
painstaking treatment in order to prevent the
entrance of decay. The part of the wound re-
quiring the greatest care is the lower part, the
stub, it might be called, of the broken half of the
tree. If the bark and wood of the stub have been
split from the rest of the trunk, they will almost

TREATMENT OF WOUNDS 47

certainly die and permit the entrance of fungi and
borers, no matter how effectively these may have
been excluded from the upper part. The de-
tached wood must be chopped or sawed away, so
as to make a good water-shed, and so as to make
it certain that there is healthy bark, in connection
with the rest of the bark of the trunk, around
every part of the wound, ready to start a callus
over it. Of course it is not to be supposed that
so large a surface will be grown over, at least for
a very long period of years. The covering given
the exposed surface should therefore be a thorough
one, of metal or reinforced asphalt. Large sur-
faces of metal on bending trees have a tendency
to tear out at the nails, a tendency, however,
which can be partly remedied by putting the metal
on in vertical strips overlapping each other.

Frost cracks and the effects of lightning will
also be included in this discussion of mechanical
injuries, for they are like the truly mechanical
ones in result if not in cause. Frost cracks are
fairly common, but their origin is not generally
understood. The cracks first come to the notice
as long but very narrow openings lengthwise of
the trunk or main branches. After one or two
seasons they usually develop long, narrow, light-
colored projecting lip-like calluses on each side of
the crack. These calluses grow and project
farther and farther from the trunk as the years

48

PRACTICAL TREE REPAIR

pass, unless a series of Vnild years permits them
to grow together. The cracks are caused by sud-
den cold snaps which very suddenly freeze the
outer layers of the sapwood while the heartwood
is still comparatively warm on account, frequently,
of its connection with the lower and warmer parts
of the soil through the taproot of the tree.
Freezing a wood cell draws the water out of the
cell wall and collects it in a crystal in the center
of the cell. When this happens the cell wall has
to contract. If, in a cold snap, the periphery of
the trunk contracts suddenly, before the inner part
has time to cool and contract proportionately,
something has to give way, and a
frost crack is the result. After the
crack is once formed sap flows into
it, and, freezing, enlarges and per-
petuates the opening. Bark pres-
sure being removed from the con-
tiguous cambium, it is stimulated to
greater than ordinary growth and
soon develops " lips." Frost cracks
should be attended to promptly, for
they are frequent sources of infec-
tion. If the injury is discovered
soon after it occurs, the crack should be painted
with liquid grafting wax, and if possible filled
with grafting wax or cotton batting dipped in hot
tar or asphalt. When calluses form their union

Cross-section
through three-
year-old frost-
crack

TREATMENT OF WOUNDS 49

should be facilitated by lightly scraping their ap-
proaching surfaces in spring. In extreme cases,
if unsightly lips have been formed which offer no
hope of ever growing together, the entire ridge
can be sawed off and the wood covered with a
strip of sheet iron. In most instances it will be
enough if a dressing (but not an unsightly one)
is kept over the crack in order to keep out fungus
spores. The cracks open in very cold weather,
and that is the best time to put in fillings or to ap-
ply dressings. Scraping the bark increases the
liability of a tree to suffer from frost cracks.

Lightning and other electrical phenomena af-
fect the trees in many different ways. Lightning
often smashes a tree all to pieces. Usually, how-
ever, it breaks a few branches out of the top and
then passes down the trunk to the ground. As
the moister parts of the tree are the best con-
ductors, the electricity almost invariably takes its
course down the cambium and the wet sapwood
just below it. The course is usually rather nar-
row, oftenest three or four inches wide, though
sometimes there are two or more such courses
down the trunk. The wood offers sufficient re-
sistance to the electricity to produce a high degree
of heat. This heat instantly vaporizes the sap
and it is the pressure of the steam thus produced
which rips the long ribbons of bark and splinters
of wood out of the trunk. The only thing to do

50 PRACTICAL TREE REPAIR

with these long scars in the tree is to clean them
of frayed and isolated bark and loosened wood
and to paint them.

There is no certainty, after all, that this treat-
ment will end the story, for lightning affects trees
in strange ways. In some cases physiological in-
juries accompany the physical ones and cause im-
mediate or gradual death. Again, a tree will be
killed by lightning without the infliction of any
physical injury. In still other cases, trees stand-
ing near a tree will succumb with it, although
apparently unhurt.

Dr. G. E. Stone, in a bulletin of the Massachu-
setts Experiment Station, says that more fre-
quently than they are severely shocked, " trees
receive only a slight discharge, which burns out
a small hole near the cambium, and the result of
such a discharge will not be noticeable until two
or three years afterward. In such a case a ridge
forms on the bark, revealing the path of dis-
charge. An examination of the tissue will dis-
close a small hole, usually not larger than the head
of a pin, running down near the cambium layer.
A wound even of this size acts as a stimulus and
induces a marked growth of the cambium. These
cases are very common but often overlooked."

In another bulletin Dr. Stone describes and
illustrates the effect of " earth discharges "
through trees. The cases he cites are largely

TREATMENT OF WOUNDS 51

localized, and he thinks the nature of the soil may
bear on the phenomenon. The discharges are
said to take place during thunder-storms, and to
be accompanied by dull reports. Only a part of
the tree is affected, as one side of the trunk and
the adjacent lower limbs. The limbs may not be
killed, even though split deeply. In a year or
two creases appear on the trunk, marking the
course of the discharge. " A very much larger
number of trees than people are aware of show
earth discharges." I have observed very similar
injuries as the result of twisting strains upon the
lower parts of limbs by the weight of snow and
ice.

CHAPTER IV

BORING INSECTS AND THEIR CON-
TROL

IN view of a prefatory statement to the effect
that this book deals only with the physical re-
pair of trees, and does not concern spraying, it
may surprise some that it should contain a chapter
on insects. There are, however, a large number
of very active insects, the bark and wood borers,
which cause injuries very similar to mechanical
injuries. They are treated with steel tools and
with dressings in much the same way that wounds
are treated, and the tree repair man is usually ex-
pected to attend to them.

No observing person who has had an intimate
acquaintance with trees for any length of time
need be told of the immense damage these insects
cause. Others may gain some conception of it
from the fact that conservative estimates place the
annual loss attributable to forest insects in this
country at $100,000,000 a year, of which the
lion's share is caused by the borers. In certain
instances the seriousness of this damage is brought
home to us with special force. Fifteen or twenty

5*

BORING INSECTS 53

years ago, to cite a familiar case, the black locust
was hailed as the great post- and tie-producer of
the future. To-day, in most parts of the country,
hardly a sound stick of it can be found. The
locust borer has made the growing of locust tim-
ber unprofitable — almost impossible.

The damage done to shade trees by these in-
sects is greater, in proportion, than that suffered
by forest trees. The reason is that almost all of
these insects prefer to attack weak trees, and
changing conditions have unfortunately so affected
our town and city trees that a very large part of
them are to a greater or less extent invalids.
They no longer make the vigorous growth they
made before streets were paved and fields were
drained, and before factories poisoned the air.
But if they are more susceptible, they are also
more valuable than they were, and we must make
every effort to save them.

It is neither possible nor desirable, in a book of
this type, to enumerate and describe the many
species of insects which in one way or another do
physical damage to the trunks and limbs of trees.
The bibliography which will be found in the ap-
pendix is sufficient evidence of the amount and
availability of the literature bearing on the sub-
ject. The number of injurious insects found in a
single locality may be very small, but the number
of species injurious in one place or another

54 PRACTICAL TREE REPAIR

throughout the country is so very large that a com-
plete account of them would be more confusing
than helpful to the average reader. I shall there-
fore describe only the principal classes of insects
damaging the bark and wood of trees, illustrating
the habits of each class by a brief account of its
more important members. Suggestions for pre-
ventive measures will be correlated with the life
histories, the proper adaptation of operations to
the seasonal changes of the insect being all-impor-
tant in this kind of work.

Almost all damage done by insects to the bark
and wood of trees is done by them while they are
in the larval or grub form. As is universally
known, insects assume two distinctly different
shapes during their lives. During the first part
of their existence they are highly specialized for
the consumption of food in large quantities and
for rapid growth. That growth completed, after
a longer or shorter period of dormant transforma-
tion (the pupal stage), they come forth in the
adult, usually winged, form, especially adapted to
reproduction and the wide distribution of the
species. It is the voracious grubs which damage
our trees.

Broadly speaking, the insects we are at present
dealing with can be divided into two classes, ac-
cording to the part of the tree in which the larva
feeds and lives. There are bark borers and wood

BORING INSECTS 55

borers. The bark borers are most dangerous;
the wood borers are perhaps most widely distrib-
uted.

The insects which do harm to the inner bark
and outer sapwood belong (as do most of the
heartwood borers) to the order Coleoptera, or
beetles, distinguished by their hard " sheath-
wings " covering the pair which are used in flight.

First among the beetles come the weevils, or
snouted beetles, a race which devotes its attention
most largely to fruits and stored nuts and grains.
Half-a-dozen representatives live in the bark of
trees. The cypress weevil mines in the bark of
injured bald cypress, and the walnut weevil is at
home in the inner bark of dying walnut trees.

Much more destructive are the bark beetles, or
" shot-hole borers " as they are often called, in
reference to the little round black-edged holes
which they make as exits from the tree. Most
of them make beautiful seaweed-like markings up-
on the surface of the wood, just beneath the bark.
The most notorious member of the family is the
hickory bark beetle, a stumpy, shining black or
reddish-brown citizen, hardly more than an eighth
of an inch long. The adults are common during
the summer, feeding on hickory twigs. The eggs
are laid in the limbs or upper trunk of the tree.
The insect excavates a vertical tunnel an inch or

56 PRACTICAL TREE REPAIR

two long, just under the bark, and along the sides
of it, rather close together, it deposits the eggs.

From Circular 144, Bureau of Entomology
Brood galleries of the hickory bark beetle on surface of wood

The young grubs strike out and excavate narrow
but widening galleries at right angles to the pri-
mary burrow or radiating from it. They hiber-
nate in these galleries, pupate in spring, and issue

BORING INSECTS 57

forth as beetles in May. Obviously, then, the
bark of affected trees should be burned, and that
of endangered trees should be given protective
dressings, by May Day. A much smaller beetle
of this race infests the oak, but in its case the
primary gallery is horizontal, so the brood gal-
leries are vertical. Still another infests wild
cherry trees; another, elms.

The next family, though it signs itself the Cer-
ambycidae, is more often spoken of as the round-
headed borers. The adults are long-horns, the
slender antennae being mostly longer than the body.
Almost all of them are borers. One is the de-
structive common elm tree borer, the adult of
which is a flat brown beetle half an inch long, with
red-bordered wing covers'. The grub is flat and
white, and makes a long, irregular burrow. It
hibernates as a grub in the tree, emerging about
the middle of April or later. Better known is its
relative, the locust borer, which works in the wood
as well as the bark. The adult is a black or brown
beetle, marked with bands of golden yellow. It
is commonly seen munching pollen on golden-rod
tops in September, at which time it lays its eggs.
The grubs live in the bark during the fall, hiber-
nate there, and burrow into the trunk, from which
they emerge late in summer. Infested locust
wood cut during the fall or winter must be burned,
used, or immersed before the following Septem-

PRACTICAL TREE REPAIR

From Department of Agriculture Yearbook, 1910
Work of the flat-headed sycamore heartwood borer

ber. If the grubs are to be dug out, the work
should be done in the fall, before they enter the
wood. The Bureau of Entomology has found
that the hibernating grubs can be killed by spray-

BORING INSECTS 59

ing the trunks with a kerosene emulsion containing
twenty-two per cent, of kerosene.

Many other members of this division are of
sinister repute. Their very names brand them
villains — the " sugar maple borer," the u poplar
girdler," and the " linden borer.1* Still another
is the round-headed apple borer, destroyer of
apple and quince trees. The striped beetle ap-
pears in June or early July, and lays its eggs, soon
after, as near as it can to the ground. On this
account protecting the base of the tree for a couple
of feet, and whitewashing the upper part of the
trunk, form an effective protection against its at-
tacks. Finally, though hardly in place here, is
the broak-necked Prionus, a huge white grub bur-
rowing into the roots and crown of apple, oak
and aspen.

The flat-headed borers are also beetles, of the
family Buprestidae. Three of them are especially
injurious. The bronze birch borer, an immigrant,
has almost exterminated the birch trees in several
cities, and also affects willow and poplar. In-
jury can be detected by a reddish discoloration a
quarter of an inch to an inch in diameter, caused
by exuding sap and ejected excrement, by the dy-
ing of the top of the tree, and by a wavy appear-
ance of the bark. The galleries, just beneath the
bark, are an eighth of an inch wide and hopelessly
tangled and irregular. The adult beetles come

6o PRACTICAL TREE REPAIR

forth in June and all infested wood should be
burned before that time. Excision is practicable
during the early stages of the attack. Preventive
dressings should be put on the trees late in May
and kept on for two months. A close relative of
the birch borer, the sinuate pear borer, is destruc-
tive in some eastern states.

Another flat-head, the two-lined chestnut borer,
is effectively helping the chestnut bark disease to
kill out the American chestnut. The beetle is
black, with two faint lines on its back, and per-
haps three-eighths of an inch long. The larva
is twice as long, and white, with a touch of brown
at each end. The mature insects appear in May
and June. Infested wood must be barked (and
the bark burned) by the first of April.

Insects which burrow simply in the wood of the
tree, not consuming any large part of cambium,
are not nearly so damaging to the tree as most of
the bark borers. Only a few species are likely to
be the objects of genuine campaigns. Many of
them, however, come to notice rather often in the
work of tree repair because of their presence in
decayed trees. Typical of the whole tribe is the
flat-headed apple borer. Its larva, remarkable
for its disproportionately large head, bores ir-
regular mines in the sapwood of the apple and
many other deciduous trees. The eggs are laid
in June or July, and the insect is not so small but

BORING INSECTS

61

that wire netting is effective against it. Protect-
ive coverings should be kept on during the period
suggested in speaking of the bronze birch borer.
The flat-headed borers do immense damage to
coniferous forest trees, causing, for instance, the

Round-headed apple tree borer, a, larva, from side; b, from
above; c, female beetle; d, pupa

oval holes so common in cheap shingles. One or
two infest sycamore, oak and beech.

Besides the flat-headed borers, the insects feed-
ing mainly on the wood are the timber worms, the
carpenter worm, and the horn-tails. Of the first
group, the chestnut timber worm is the most im-
portant. It is responsible for the holes so com-
monly observed in chestnut lumber. There is
little to be done with it directly, but preventive
measures, as the destruction of dead and dying
trees and limbs, are effective.

62 PRACTICAL TREE REPAIR

First among the carpenter worms is the leopard
moth, introduced from Europe some thirty years
ago. Many trees, fruit and shade, are attacked
by it. The larva, which reaches a length of two
inches, is yellowish or pinkish, with a dark spot

l§fe:.
''•%A2iLV

Circular 109, Bureau, of Entomology

The leopard moth, a, adult female; b, adult male; c,
larva; d, empty pupal

at each end. It is sparsely hairy and covered
with prominent tubercles. The moths are hairy,
with semi-transparent white wings dotted with
dark bluish or greenish spots. They appear dur-
ing summer, beginning in May. The eggs are
laid soon after, and the young grubs burrow into

BORING INSECTS 63

a twig or branch. When they outgrow this first
branch they migrate to a larger one. They fre-
quently girdle a branch by burrowing around its
circumference just under the bark. The position
of the burrows is indicated by the matted sawdust
at their mouths. Pruning affected small limbs is
beneficial, on account of the grub's habit of mi-
grating. Fumigating with carbon bisulphide and
killing with wires also have their value. The
larvae live two years, spending the second year in
the large limbs and trunk. A campaign against
them should include one treatment of those parts
of the tree in the late summer of two successive
years.

The last group of insects worthy of mention as
wood borers is the horn-tail tribe, or wood wasps.
The commonest species is the u pigeon tremex."
The adult is a large, stocky, wasp-like insect, with
two pairs of transparent brownish wings. The
body is brown with lighter bands across the ab-
domen, at the posterior end of which there are in
the female three stout spines, used in depositing
the eggs in the bark. The larva is stout and
cylindrical, with a small head. The adults
emerge in summer and lay soon after. The bur-
rows of the grubs and the holes made in the bark
by the escaping insects are round, and nearly a
quarter of an inch in diameter. The insect does
not do great damage on account of the small

64 PRACTICAL TREE REPAIR

amount of cambium it destroys. The only
measure which can be taken against it is the de-
struction of infested trees. The main reason for
describing it here is to prevent confusion of this
insect with a beneficial parasite upon it which is
often blamed for the work of the tremex. The
parasite is an ichneumon fly, Thalessa lunator,
which slightly resembles the tremex in appearance,
though the ovipositor of the female, instead of
being half an inch, is three or four inches long.
The male has a slender abdomen, and both have
dark spots on the first pair of wings. The Tha-
less a deposits its egg in the burrow of the tremex,
and its larva causes the death of the tremex larva.

Such are the principal insect enemies of trees
with which the tree repairer is likely to have to
deal.

All these pests must be fought relentlessly, and
it is the duty of the local government, and at times
of the State and National Governments, to lead
in the fight. The best line of campaign is preven-
tion, and effective preventive measures must
usually be undertaken on a larger scale than is
possible to any but the largest private owners.
Insomuch as most of these insects prefer, and
increase rapidly upon, weak and dying trees, the
authorities should see to it, in so far as they have
power, that dying trees are removed and burned,
and that weak ones are pruned and fertilized into

BORING INSECTS 65

vigor — or else that they go the way of the dying
trees. Allotment companies are great sinners in
this connection. They carry out grading and
drainage operations which cause the death of
hundreds of trees, whose bark and trunk are soon
fairly alive with busy hosts of insects. People
who buy lots in such vicinities must keep watch on
their own trees, and should use their influence to
have the sources of infection removed.

In addition to these measures, which are simply
the application of good silvicultural principles to
the trees of the city, considered together as a
forest, it is extremely important that all trees, and
especially trees of a threatened species, or trees in
an infested region, should be kept in good health.
In some cases fertilization alone will be found a
sufficient check upon an epidemic of bark beetles.
The most destructive species affect only weakened
trees. The way to make them pass by your trees
is to see that your trees have a good healthy flow
of sap. That means " Water and manure ! "

We have, then, these rules for the prevention
of insect epidemics and attacks:

1. In planting, select trees suited to the soil
and locality, so that they can easily be kept in a
thrifty, resistant condition.

2. In the case of established, as well as newly
planted trees, see that the soil is right as regards
fertility and physical condition, and that the trees

66 PRACTICAL TREE REPAIR

have the proper amount of water. That is, keep
all trees vigorous.

3. Cut and burn, or at least bark, all dead
and, especially, dying trees not later than the first
of April of each year, unless the habits of some
particular pest indicate another season as the cor-
rect one.

Under certain conditions, however, especially
in orchards, the use of a direct protective cover-
ing or dressing may be the only way to prevent
an attack. These take several forms. Against
the round-headed apple and quince borers and the
peach borers, a covering of tough paper or fine
wire netting, tied tight above and heeled two
inches deep with soil below, make effective pro-
tections.

Of repulsive dressings there are a large num-
ber, though less often recommended now than
formerly. " Raupenleim," for instance, sold by
the Bowker Fertilizer Company, of Boston, is
very effective as an all-over covering. Mixtures
containing vaseline or tar should not be used in
large quantities. The thinner applications, which
depend mostly upon their smells for their effective-
ness, have also much value, though they must
usually be renewed at intervals during the summer.
The best of them is probably a pound of whale-
oil soap dissolved in a gallon of water and re-
inforced with two ounces of carbolic acid. The

BORING INSECTS 67

trunks and lower limbs of the trees should be
painted with the mixture at intervals of two or
three weeks during the danger season.

Similar in results, but unlike in the way they
are attained, are whitewash and cement paint.
Whitewash must be applied heavily and very
thoroughly, the loose bark being previously
brushed off. It must be renewed as often as the
weather destroys its completeness of covering.
Cement paint, made by mixing, to the consistency
of heavy paint, Portland cement in skimmed milk,
makes an extremely effective protection and lasts
the whole season. It, as also whitewash, can be
colored to suit the operator's fancy.

These campaigns must of course be planned in
advance. Above all, the egg-laying season of the
particular insect in hand must be determined. If
doubt as to that point exists, consult the entomolo-
gist of your State Experiment Station, sending
him a full description of the injury, and, if possi-
ble, specimens of the insect.

Preventive measures such as these, however, are
not exactly tree repairing.

The only way to fight the borers after they have
attacked a tree is to dig them out or kill them indi-
vidually in their burrows. The work can be done
at any time, but perhaps late summer and early fall
are the best. The operator should provide him-
self with the tools ordinarily used in treating bark

68 PRACTICAL TREE REPAIR

wounds. In addition a half-inch curved wood-
carver's gouge will be handy. Some steel wire
will be needed for probing the burrows. Differ-
ent kinds of wire suit different jobs, sometimes a
stiff, and sometimes a soft wire being the best.
The materials required are putty, which is the
handiest thing with which to plug up small holes,
though some people prefer the more expensive
grafting wax, carbon bisulphide for poisoning
grubs in their holes, and the ever-essential paint
or tar.

The attack begins with a careful study of the
enemy's plan of campaign — determining whether
or not more than one age of larvae is present,
whether, say, some burrows contain one-year
larvae and others two-year; discerning the signs,
often very minute, which mark the presence of a
burrow; and investigating carefully the direction
and length of the burrow and the comparative
effectiveness of the probing and poisoning methods
of attack. If it is found that the burrow is large
enough and straight enough to make it possible to
kill the larvae by probing the burrows with a wire,
that method should be adopted. It is far the most
rapid. After the hole is probed it must be
plugged up with putty. If there is any dead bark
about the entrance of the burrow (and many
borers live for a time just under the bark before

BORING INSECTS 69

they enter the wood) it must be cut away and the
wound must be painted.

If, on the contrary, probing the burrow is not
rewarded by that peculiar and gratifying sound
which makes known that the larva has been
crushed, poisoning must be resorted to. Carbon
bisulphide is almost invariably used for this pur-
pose, because of its cheapness and convenience.
It is a highly volatile fluid, giving off a gas which
is deadly to all animals. It is inflammable, and
he who smokes while he uses it had better look
out for the fool-killer. As a rule, it comes in
half-pint tins, stopped with a cork. There are
several ways of applying it to the burrows. I
carry around a pocketful of little bits of cloth, say
an inch square. When I have opened up the
mouth of a burrow I take one of these bits of cloth
with a pair of forceps, dip it into the carbon, and
then insert it in the hole, which is then, of course,
immediately plugged with putty. The more usual
way, though, is to apply the fluid with a small
syringe, those of glass being handiest. About
half a teaspoonful or a little less is required for
each hole.

It is extremely essential, in going over a tree,
that every burrow be found, and that the eye be
trained to detect the least indication of the pres-
ence of a borer. Every suspicious-looking spot

70 PRACTICAL TREE REPAIR

must be investigated, until the true signs are mas-
tered. If the whole tree is infested and an effort
is made, nevertheless, to save it, the trunk should
be done thoroughly, whether there is time to do
the limbs or not.

In his important work on forest insects (Fifth
Report of the United States Entomological Com-
mission, 1890) Prof. A. S. Packard describes a
method of combating bark borers which had been
tried, apparently with success, in Belgium. It
was discovered that a full flow of sap killed the
larvae, doubtless the reason the insects prefer
weak trees. Insomuch as removing bark pressure
increases sap flow, particularly in spring, the ex-
periment was tried of paring off the outer layers
of the cortex, down to say a quarter of an inch
or a little less of the cambium, over the affected
areas in old elms. The resultant flood of sap
killed the grubs. The writer has had no personal
experience with this method. He would suppose
that it would be hard to say just which trees and
what parts of them were invaded by the borers
until it was too late for the work to be effective.
A protective covering of cement paint would prob-
ably be necessary to prevent undue drying of the
exposed inner bark.

Such measures as this, and not less the usual
curative operations, ought invariably to be supple-
mented by the use of stimulating manures.

CHAPTER V
ROT-FUNGI AND THEIR WORK

HOLLOW trees are caused by fungi. If it
were not for rot-producing fungi trees
would live twice as long as they do, lumber would
cost half as much, and this book would not con-
tain half as many pages as it does. These fungi
are plants of a low order, plants in which there
is no, or little, differentiation into root, stem, and
leaf. Every bacterium is a fungus; so is every
mold, mildew, smut, and mushroom. The main
respect in which these plants are alike is that they
do not contain chlorophyll, the green coloring
matter characteristic of plant cells which carry on
the work of photosynthesis, or the utilization of
the carbon in the air. That is, they cannot make
carbohydrates out of water and carbon dioxide,
as green plants do. The same is true of animals,
and the fungi are like animals in that they are ab-
solutely dependent for their sustenance upon ma-
terials elaborated by chlorophyll plants, either in
the form in which those materials are produced
by the plants or as they may be worked over by
plant-eating animals. In other words, fungi live

71

72 PRACTICAL TREE REPAIR

upon living or dead plants or animals. Those
which subsist upon living organisms are called
parasites; those which live on dead matter are
saprophytes. This division, however, is not iron-
clad, for some fungi part of the time follow the
policy of one class and part of the time that of the
other. Fungi which can live only upon the heart-
wood of trees are of course really saprophytic, be-
cause the heartwood is dead.

Intelligently to prevent and as far as possible
remedy the attacks of rot-producing fungi, it is
essential that the man who is doing tree repair
work should study and understand their manner
of growth and distribution, and should be able to
distinguish the most important species, just as a
good physician must know all that has been dis-
covered about typhus and tuberculosis bacilli.

The life cycle of a fungus is superficially quite
like that of one of the higher plants. The mush-
rooms and hoof-like or shelf-like growths we see
so often on dead and decayed trees are the fruit-
ing bodies of rot-producing fungi. From their
lower surfaces come thousands of little dust-like
cells, called spores, which have the capacity of
vegetating like seeds and of growing into new
fungus plants. Let us suppose that such a spore,
from the fruiting-body of the " white heart-rot,"
is wafted away by the wind and falls upon an old
bark-wound in the trunk of a maple, the surface

ROT-FUNGI AND THEIR WORK 73

of which is now checked and weathered and moist.
Here all the conditions are favorable, and in a
few days the spore begins to grow and sends out
a minute root-like organ containing living proto-
plasm. This hypha grows and branches and soon
makes up quite a mass of fibers, gradually working
its way into the heart of the tree. The hyphae,
considered together, are called the mycelium of
the fungus, and really constitute the fungus plant.
The brackets and mushrooms which appear on the
outside of the trunk are special bodies — in a way,
fruits — developed by the plant solely for the pro-
duction of spores, and called, on that account,
sporophores. The living tips of the hyphae make
their way through the wood in various ways.
Some work in between the cells, sending little root-
like branches through the walls of the cells to
suck out what is nourishing of their contents. In
other cases the tips of the hyphae exude ferments
which dissolve the cell walls and permit the hyphae
to grow freely throughout the wood, consuming
part of it and leaving the rest fragile and dis-
united.

Although the hyphae of the fungus are quite in-
visible to the naked eye, the result of their work
is easily detected. The wood changes in color,
texture, and weight. These changes, however,
are to a large extent gradual. In the case of some
fungi it is very difficult to draw a line in a cross-

74

PRACTICAL TREE REPAIR

•«.«»
».••

» •;
• :

section of a rotted trunk, between the diseased
wood and the sound wood. Sometimes the wood
is discolored before it is actually invaded. In
other forms, the wood is invaded a considerable
distance before any change is
observable to the unaided eye.
When a fungus is working up
a tree, also, it often sends an
advance guard of mycelium
up the very center of the
trunk, where the soft pith
makes its progress easy. All
these facts make it much more
difficult than it would other-
wise be to make a complete
sporophore to exc;sjon of decayed wood.

As regards the rate at
which decay spreads through wood, but little is
definitely known. It is certain that different de-
cays grow at different rates, and that the same
decay spreads at different rates in different trees.
The indications are that, in the main, de-
cays spread very slowly — sometimes only a little
faster than the wood is built up by the cambium.
After the passage of a greater or less period of
time, often amounting to many years, a denser
mass of hyphae than usual gathers at some point
near the outer surface of the host, usually at a
wound, a rotted knot-hole, or the burrow of a

.•••:•!

Section of a decayed

trunk, showing reia-

ROT-FUNGI AND THEIR WORK 75

boring insect. From this mass there is sent out
a more or less highly differentiated and completely
formed body, the purpose of which is to develop
and disseminate the spores. The appearance of
sporophores on a tree is of course conclusive evi-
dence of the presence of decay within the tree, and
usually a large amount of decay, for the fruiting
bodies are not produced until the fungus plant has
made a strong growth. In certain cases sporo-
phores are not produced until the mycelium has
exhausted the available supply of nourishment.
Frequently a fungus subsisting in a living tree does
not send out sporophores until its host dies. The
moral is, not to suppose, just because there are no
mushrooms on your trees, that there is no decay
inside of them.

The many hundred rot-producing fungi affect-
ing living trees fall readily into four groups, ac-
cording as they attack mainly the bark, sapwood,
heartwood, or roots. For the present purpose it
will be enough to describe one or two of the more
important members of each group. Readers who
desire fuller information are referred to the
bibliography.

Of bark decays the commonest and best known
are the apple bark rots and the chestnut bark dis-
ease. There are a number of fungi which kill
larger or smaller areas of the bark on apple limbs
and twigs. Several of them, as the bitter rot, also

76 PRACTICAL TREE REPAIR

attack the fruit The apple blister canker (Nu-
mulana discreta) is one of the most destructive.
It is a wound parasite, starting growth wherever a
bit of dry wood presents itself. For a time it
grows in the heartwood, then spreads into the
bark, rapidly killing a large patch. The affected
area becomes brown, sunken, and blistered. In
a year or two the branch is girdled and killed.
Pruned orchards should be sprayed promptly with
a fungicide, and all large wounds should be
dressed with an antiseptic. Small branches which
are inoculated should be removed. On large
limbs the affected areas should be cut away with
a draw-shave, the wound being carefully dressed.
The man who is repairing trees must know the
apple bark rots. When he finds a tree seriously
affected by onex>f them he must not fuss with
cavities in the tree until the far more dangerous
bark rot is cleaned out.

The chestnut bark disease is not unlike the
blister canker. The mycelium of the fungus
enters the bark through small wounds. It grows
in the bark and cambium, spreading until it girdles
the limb and starves the outlying parts. The
bark of the affected areas becomes light brown
and shrinks as it dries. This fungus is spreading
rapidly in the eastern states. Many of the state
forestry departments, as well as the National Gov-
ernment, have issued bulletins on the disease, di-

ROT-FUNGI AND THEIR WORK 77

recting owners of chestnut timber as to the way
to handle and use affected trees. There is no
wholesale method of combating the disease.

Valuable trees can, however, be treated indi-
vidually. In an interesting article in the Febru-
ary, 1913, American City Mr. R. G. Pierce de-
scribes his system of treatment.

" All the diseased bark or wood must be re-
moved from the tree and burned. The tools,
such as gouge, chisel, knife or hand ax, used in
this cutting-out work, as well as the cut surface,
should be thoroughly sterilized. The wound
after sterilization should be covered with some
water-proofing. . . ." Mr. Pierce goes on to de-
scribe his method of operating in detail. Small
branches which are affected he removes with a
sterilized saw. Diseased areas on larger limbs
he cuts out, cutting into the wood a depth of five
or six annual rings, and removing at least an
inch of healthy bark around the discolored area.
Tools must be sterilized (as by dipping in creo-
sote) before the final layer of wood is removed.
Mr. Pierce catches the diseased bark thus gouged
out in a bag to prevent it from infecting lower
branches in its fall.

The fungi of the next group, those causing
decay of the sapwood, are probably in no case
true parasites. When they attack living trees it
is only very weak trees which are seriously dam-

78 PRACTICAL TREE REPAIR

aged. They very quickly attack unseasoned tim-
ber, standing or felled. For instance, Polystictus
pergamenus is frequently found growing on trees
which have been seriously injured by fire, frost,
or sunscald. It attacks the .dead bark first,
spreading later into the sapwood. In a few years
it sends out hundreds of little shelf-like, leathery
sporophores. The prompt cleaning away of every
patch of dead bark and the dressing of wounds
are the only preventive measures, and of course
complete excision is the only cure.

The third group is the most important of all.
Almost all its members are wound rots, entering
the tree through exposed surfaces of wood.
They make their way from the wounded spot into
the heart of the tree, and grow up and down in
the heartwood. The destruction of the heart-
wood is not immediately harmful to the tree, and
some fungi cannot spread outside of the heart-
wood. Others, the majority, though they cannot
actually invade healthy sapwood vessels, can work
their way into the sapwood by virtue of certain
changes, approximating a change into heartwood,
which take place in the sapwood immediately con-
tiguous to the decay. These changes take place
most readily where the sapwood has become drier
than usual, as through the death of a root just be-
low it, or the removal of the bark covering it.
Thus the fungus can work its way to the surface

ROT-FUNGI AND THEIR WORK 79

at a wound or weakened spot, and push out sporo-
phores. The invasion of normal sapwood by
heartwood rots is, however, very slow, and it al-
most never happens that a tree is strangled and
killed by such a fungus. What the heart rots do
is to weaken the support of the tree, making it lia-
ble to destruction by storms.

Perhaps the commonest and most destructive of
the fungi inhabiting the heartwood of trees is the
"white heart rot " (Fomes igniarius). It is
found in every part of the world. In this country
it most frequently attacks beech, aspen, willow,
maple, walnut, hickory, apple and oak.

Entering through wounds or the stubs of dead
limbs, the fungus attacks the heartwood of the
tree. Von Schrenk and Spaulding give the fol-
lowing description of the effect of the fungus upon
the wood of the tree : ' The diseased wood is
very sharply bounded from the healthy wood by
black layers about one-eighth to one-sixteenth of
an inch in width. There may be but a single one
or there may be several arranged more or less
concentrically. Just outside of these layers there
is a layer consisting of from three to six annual
rings, which is darker in color than the normal
wood because of the infiltration into the same of
products of the decomposed wood. . . . The
black layers never exactly follow the annual rings
of growth. . . . The completely rotted wood is

8o PRACTICAL TREE REPAIR

white to light yellowish in color, according to the
species of tree in which the fungus is growing.
When rubbed between the fingers it breaks up into
fine flakes, but does not powder."

The fungus does not normally develop sporo-
phores until many years after infection. The
woody fruiting body, though somewhat variable
in appearance, is usually hoof-shaped, with a hard
outer layer, brownish or blackish in color. To
the lower surface of the hoof there is annually
added a gray or reddish-brown layer of pores in
which are produced the spores which reproduce
the fungus. The first sporophores usually appear
at the point of original infection. Later ones
may break out wherever the decay comes close to
the surface of the wood. The sporophores are
by no means so common as the rot. In many
groves of infected trees not a single sporophore
will be found.

A decay of which the sporophores of the causal
fungus are more familiar than those of the fungus
just described is the red heart rot induced by
Polyporus sulphur eus. It attacks both coniferous
and deciduous trees, particularly the oak, chestnut,
walnut, maple, apple, pear, and hemlock. Wood
destroyed by this fungus becomes red-brown and
full of checks, in all three planes, which fill with
white sheets of mycelium. Later the powdery
remains of the wood can be shaken out, exposing

Fruiting bodies of white heart-rot fungus «>n aspen
(Bureau of Plant Industry. Bulletin 149)

ROT-FUNGI AND THEIR WORK 81

the mycelial framework. Trees long affected
are always hollow with masses of the powdery
rotten wood, alive with insects, at the bottom of
the cavity.

The mushrooms of the red heart rot, which are
edible when young, appear in late summer but do
not persist long.

Hydnum erinaceus, the " coral mushrooms,"
causes a decay of oaks and maples characterized
by the softness and moistness of the decayed wood.
" The diseased wood in its final stages," say von
Schrenk and Spaulding, " is soft and mushy, so
that when squeezed considerable water flows out.
Trees in an advanced state of decay have numer-
ous large holes in the heartwood, which are filled
with masses of light yellowish, fluffy fungous my-
celium." The mushrooms, much sought by epi-
cures in that sort of delicacy, are lumpy, soft,
moist-looking, and crowded underneath with spike-
like teeth bearing the spores.

Root rots are fortunately not so common as
heart rots, for they are at once deadly and almost
impossible to combat. The only well-known
species is the honey mushroom, Armillaria mellea.
The fruiting bodies occur in masses at the base of
the affected tree or on the surface of the soil above
a large root. The individual mushrooms are
rather small, honey colored, and specked with
white. The stem has a swollen base and a ring

82 PRACTICAL TREE REPAIR

around its throat. The gills are white. The
honey mushroom produces growths sometimes
called " shoe strings " which are commonly seen
under the rotten bark of dead stumps, and in the
surrounding soil. They are flat (in open soil
round) black strands of hard-woven mycelium.
It is at the ends of them that the mushrooms are
found. The fungus enters through a wounded
root, spreading into and killing the cambium, and
progressing from root to root by means of the
" shoe strings." When most of the roots have
been killed up to the trunk the tree suddenly blows
over. The rotten roots should be dug out if pos-
sible, and no new tree should be planted near by
for several years.

In addition to these fungi which cause disease
in living trees, there are two found only on dead
trees or branches which are so common that they
must at least be referred to. One is Fomes ap-
planatus, the common brown and white shelf-
fungus. It is found only on dead trees or dead
parts of trees. The other is Polystictus versi-
color, the variously tinted and striped papery little
shelf-like sporophores of which are omnipresent
in the woods and along the railroad track. It
attacks but one tree in the living state — the
catalpa.

Below wounds and in the vicinity of cracks in
elm, maple, and horsechestnut trees there is often

ROT-FUNGI AND THEIR WORK 83

seen a whitish or brownish stain, caused by slimy
exudations from the cut or fractured wood. Such
a flow is called a slime-flux. The flux is charac-
terized, in addition to its appearance, by a sour,

Sporophores of Fames applanatus on dead maple stump

yeasty smell. Slime-fluxes are probably due to
the growth of algae, low fungous forms, as bacteria
and yeast, and often animalcules, in the sap which
escapes naturally, at the time of the original injury
to the tree, from the cambium and sapwood. The
growth of these minute organisms causes the for-

84 PRACTICAL TREE REPAIR

mation of a slimy covering over the exposed wood.
This covering is of a liquescent nature — attract-
ing water. It thus draws the watery sap from the
sapwood, preventing the natural drying-out and
closing of the sap-conducting tubes. The process
continues for an indefinite period, until the cam-
bium in the vicinity of, and especially below, the
source of the flux is killed. It, and later the inner
bark, turns brown, and the bark is easily separated
from the wood. The deleterious effect of the
flux upon bark tends to prevent the healing, by
calluses, of the wound, and contributes further
to the permanence of the flux, which usually con-
tinues until higher fungi invade the area and kill
the wood from which the flux had been drawing
sap. This is a rough and ready account of a
phenomenon scientists are still studying, but it will
do for our purpose.

The disposition of wounds to be affected by
slime-flux can be diminished by pruning in the dor-
mant season and by dressing wounds promptly
with a penetrating antiseptic such as creosote.
Curative measures must of course be carried out
in the dormant season. If it is a flat pruning
wound scrape the cut surface and pare away all
dead bark. Then apply hot creosote or hot tar,
following later with a second coat. If the flux
exudes from a hole, clean out the place with a
gouge, making the excision a thorough one. Then

ROT-FUNGI AND THEIR WORK 85

treat the cut surface as just suggested, preferably
drying out the hole with a gasoline torch before-
hand. Do not fill such a hole until the success of
the cure is certain. If the trouble arises in a crack
which cannot be gouged out, the only things to do
are to make the drainage as good as possible and
to spray the crack often with a copper solution.
There seems to be no better place than this to
throw in a reference to mistletoe, which is a serious
pest in some parts of the South. When possible
the infested limbs should be removed. Attempts
to prune off the parasite, or even to gouge out its
roots, are not often successful.

CHAPTER VI

THE VALUE AND FUNCTION OF FILL-
ING TREES

AFTER finishing this chapter some readers
may think that the writer is like the doctor
who, as a physician, gave his patient some medi-
cine, and then, as a friend, advised him not to take
it. But he will not plead guilty to such a charge.
He believes that " tree surgery " has a function
and real value, but he thinks there are limits to
that value, and this chapter, roughly speaking, is
an attempt to define those limits.

The first thing to be admitted, or stated, is that
the art of filling cavities in trees is still in an ex-
perimental stage, the value of the work, and even
the right ways of doing it, being as yet quite un-
certain. This statement may shock some people
who have seen fillings done by the better work-
men, and who have read or heard the claims of
the " tree surgeons." Yet with that statement
nearly every experienced arboriculturist in the
country will agree, and it is a statement which can
be proved.

To begin with, we must study the effect of decay

86

FILLING TREES 87

on trees when the tree repairer does not interfere.
One of the most surprising facts about the normal
course of decay is the extreme slowness with which
it does its work. This will be branded as the
rankest heresy by every " tree doctor." They
have made every effort to create the impression
that the least sign of decay, if untreated, will be
followed by speedy dissolution and certain ruin.
But the proof is all on the other side. Common
observation and the records of history and science,
all agree that perfectly hollow trees frequently
survive and flourish for very long periods. Liter-
ature and legend are full of references to such
trees. No one who has gone back to the old
farm of his youth has failed to recognize many
of the " bee trees " and " coon trees " and "old
hollow apple trees," which were seemingly no
more hollow than they had been a decade or two
before. In 1687 the Charter Oak contained a
hollow large enough to hide the charter of Con-
necticut in. If there had been tree doctors in
that day they would have affirmed that only a
prompt filling of concrete would prevent the early
death of the tree. Yet not until 1856 did it suc-
cumb, still green, to the storms of New England.
The trees themselves, in many ways, offer evi-
dence of the time decay may continue without be-
ing fatal. A tree makes an effort to close a
wound by rolling a callus over it from the sides.

88 PRACTICAL TREE REPAIR

If a cavity develops where the bark has been
wounded, the callus has no support, and as it
grows it does not bridge over the cavity, but simply
rolls inward, gradually becoming a great fold.
Insomuch as the fold increases, like other wood,
by annual layers, it is easy to count or estimate,
in a cross-section through such a fold, the number
of years since the tree became hollow. Folds of
this kind are not infrequently found to be half a
century old, or even a century.

We can even look at the teeth, so to speak, of
of the rot-producing fungi themselves. Many of
these fungi have a woody fruiting body, or sporo-
phore, which adds to itself each year a new layer
of spore-bearing tubes. The number of layers
therefore indicates the age of the sporophore.
The hoof fungus Fames igniarius, is such a one.
Sporophores of the hoof fungus have been found
which contained eighty annual layers. And it
must not be forgotten that the fungus may have
lived in the tree many years before it produced a
sporophore.

All these facts, taken together, conclusively
demonstrate that the decay of trees is sometimes
an extremely slow process, and all indications
point to the conclusion that it is normally such.

" But," it may be objected, " tuberculosis is
often a very slow disease. Is that, then, any
reason for not trying to cure it?" Not by any

FILLING TREES 89

means, but it is a very good reason for not too
hastily concluding that the disease is cured by
a certain treatment, just because the patient sur-
vives that treatment for a year or two. And
that is just the point. The tree surgeons, if we
express doubts as to the effectiveness of their work,
will show us examples of it which are eight or ten
years old, and ask if any further proof is neces-
sary. It surely is. We must be convinced that
the tree would not now be in as good condition
as it is if the filling had not been put in. That,
of course, is not an easy thing to do, because no
two trees are alike, and because of the impossibil-
ity of seeing what is going on inside of a filled
tree. No definite conclusion can be arrived at as
to the effectiveness of large fillings in decayed
trees until impartial observers have studied a large
number of filled and unfilled trees for a long period
of years. This conclusion obviously works both
ways. If it will take a long time to prove that
filling trees works, so will it take a long time to
prove that it doesn't work, and the only way to
learn is to try. With this the writer agrees per-
fectly, because it is an admission of his thesis, that
tree surgery is still in an experimental stage.

There is one aspect of the filling of trees, how-
ever, about which doubt no longer exists, and that
is its expensiveness. It requires a great deal of
hard as well as skilled labor to remove the decayed

9o PRACTICAL TREE REPAIR

wood from a rotting tree and to put in a filling of
concrete or asphalt. When there are many trees,
it is easy to see that the bill is likely to be a large
one. Few would object to the cost, however, if
paying the bill meant that the trees were perma-
nently restored to health and vigor. Few would
object if they were sure that, whatever the result,
the money was spent in the way in which it would
do the trees the most good. But not many of us
have absolutely unlimited funds to expend on our
trees, and we want to be reasonably sure, if we
spend a hundred dollars for having a tree filled
with concrete, that the tree will be helped thereby,
and helped more than it would be by any other
expenditure of the hundred dollars.

It is this condition of affairs which makes it so
essential that the owners of trees, and the land-
scape architects and other professional men who
are called upon to advise them, should be in-
formed as to the principles to apply in determining
whether a certain tree ought to be filled or not.
As a help in that direction, certain rules can be
laid down, but it must be remembered that they
are not iron-clad, and that they are subject to the
supreme rule that circumstances alter cases.

The first rule is almost self-evident, and it
would not seem necessary to state it, if it had not
frequently been violated by tree surgeons. It is
that no expensive cavity work should be put into

FILLING TREES 91

a tree belonging to a species which, locally or
generally, is doomed to destruction by the attacks
of insects or fungous diseases. In some parts of
New England this principle would rule out work
on old elms, on account of the havoc wrought by
the elm-leaf beetle and the leopard moth. The
rapid spread of the chestnut bark disease makes
it almost foolhardy to put much money into chest-
nut trees within two hundred and fifty miles of
New York. Even beyond that radius, it is doubt-
ful whether work is admissible which looks for-
ward fifteen or twenty years.

The second rule is to the effect that it is usually
unwise to spend much money filling trees that
stand in a grove or woods, where the mass of the
foliage counts for more than the individual trees.
In such a case the grove should be handled as a
whole. Its effect as a whole, the thickness and
the color of the foliage and the thriftiness of the
trees, is likely to be improved far more by enrich-
ing the soil, by installing a watering system, or
by planting young trees, than by the expenditure
of the same amount of money in filling cavities
in one or two of the trees. In this connection it
must be remembered that in the absence of the
elementary requirements of tree life, water and
good soil, the other trees in the grove will one
by one need more or less expensive doctoring. If
a veteran of the grove becomes weak and threatens

92 PRACTICAL TREE REPAIR

to succumb to the storms, prune it back severely,
perhaps brace it to its stronger neighbors, fertilize
it, and plant a young tree or two near by. The
chances are good that the old tree will become
a sturdy specimen and thrive for several decades.
The young tree, in the meantime, will grow to fair
size, and will be ready to take the veteran's place.
If the grove is to be permanent it must always con-
tain young trees as well as old ones.

In the third place, expensive fillings should not
be put into trees in a region where there is a high
mortality rate (either among all trees, or simply
in the species to which the decaying tree belongs)
on account of gradual changes in the environment.
Such regions of high mortality are common near
cities. They are oftenest caused by the lowering
of the water level and the consequent drying of
the soil, as a result of draining, street-paving, the
destruction of the forest floor covering, and the
compacting of the surface soil. They are also
caused by the contamination of the atmosphere
by factories. When such a state of things exists,
or threatens to exist, it is obviously unwise to spend
money on work which cannot in any way diminish
the risk from the prevalent adverse conditions.
If there is money to be spent upon the trees in such
a locality, it should be spent, if at all, in an effort
to restore the natural conditions for want of which
the trees are dying, and preferably in improving

FILLING TREES 93

the soil. Money spent on the soil is rarely
wasted. If it does not save the old trees, it will
at least give their young successors a good start
in life. If the trees survive and adjust them-
selves to the new environment, the ones that re-
quire it can safely be filled or otherwise repaired.

The fourth rule is scarcely more than a special
case under the last. A tree which has just under-
gone a distinct change of surroundings should not
be filled. Such a change might be, for instance,
the building of a house very near to the tree, with
the resultant cutting of roots and branches, or the
simultaneous removal of a number of close
neighbors, or the installation of a drainage sys-
tem. A number of years should be allowed to
elapse in such cases, before the tree is filled, in
case it contains a large cavity. Filling, which
can in no way help the tree to meet the new con-
ditions, should be deferred until it is certain that
the tree will survive the change of environment.

Expensive cavity work should not be put into a
tree unless the other needs of the trees have been,
and are going to be, attended to. If a man is
starving to death it does not lessen his misery to
reflect that his bones are strong enough to sup-
port a fat man. Decaying trees can survive with-
out fillings — even flourish without them — but
no tree can long survive or flourish without food
and water and protection from its insect enemies.

94 PRACTICAL TREE REPAIR

Nor should any tree receive costly surgical care
if it is weak and making little growth. The great
army of bark and wood borers and other insect
enemies ready at any time to swoop down upon a
weakening tree, makes the expectation of life of a
weak tree very precarious. Common sense in-
dicates that no large sums ought to be risked on
sickly trees.

Again, only after very careful consideration
should a hollow tree be filled up which has com-
pleted or nearly completed the span of life natural
to that species in that climate and soil. Some-
times such old trees can be reinvigorated, but in
every case the measures calculated to restore youth-
ful vigor should be carried out and their success
assured, before much filling is done.

Finally, from the fact that a tree is hollow it
does not necessarily follow that a concrete or as-
phalt filling is " indicated," as the doctors say.
Some decays eat out the entire heartwood and die
out with the destruction of the affected wood. In
such cases filling is of but little value. The decay
has done its work and it is too late to stop it. The
drainage of the cavity is usually good, and the
inner surface is often so weathered that it is as
resistant as a seasoned plank. Such a condition of
affairs is often observed in old sycamores. No
further treatment is justified than smoothing and
painting the walls of the cavity and carefully brae-

FILLING TREES 95

ing the tree. Equally futile is the attempt which
is sometimes made to remedy chestnut trees which
have been completely hollow by the powdery red
heart rot.

These general rules for the avoidance of unwise
expenditures in large tree repair projects must
be supplemented by a discussion of the comparative
importance of various kinds of cavities, and a
classification of them with reference to ease of ex-
ecution and certainty of success.

As a preliminary of such classification, how-
ever, we must formulate a statement of the ends
aimed at in the filling of cavities, because our
decision as to the probability of success in filling
each type of cavity will depend upon the degree
to which the purposes of the filling can be attained
under the peculiar conditions presented by that
type of cavity. Briefly stated, holes in trees are
cleaned out and filled with these three purposes
in mind: First, to stop decay by removing all
the fungus. Second, to prevent the entrance of
fungi and insects by coating all exposed wood with
a protective dressing, by filling the cavity with
cement or asphalt, and by facilitating the healing
of the wound. The third purpose is to strengthen
the tree.

These different purposes are attained with vary-
ing degrees of success. The first purpose can
sometimes be attained perfectly, especially in cases

96 PRACTICAL TREE REPAIR

of limited and local infection by a fungus which
produces a definite line of demarcation between the
sound wood and the diseased. At other times
it is absolutely impossible of attainment, and is fre-
quently impossible at a reasonable cost. The
second intention is subject to about the same
chances of success, depending upon the kind of
tree and the shape and location of the incision.
As regards the third purpose, it may be said that
fillings add little or nothing, of themselves, to the
strength of the tree. The iron braces usually put
in to hold the filling in place, however, have some
strengthening effect. But this phase of the work
will be taken up in greater detail in the following
chapter.

These are the things that the tree surgeons do,
but they are not, it is true, the only things they
claim to do. They have been able to create in
people's minds the impression that filling a tree
constitutes an immediate relief from some sort of
canker which saps the life of the tree, and that the
process of filling exerts a direct physiological in-
fluence, at once increasing the tree's vigor and re-
storing, so to speak, its good spirits. This kind
of talk has caused the breach which undoubtedly
exists (and much to the detriment of the real
science of tree repair) between the tree surgeons
and the arboriculturists and landscape architects.

A gentleman whose knowledge of plant physi-

FILLING TREES 97

ology was gleaned from the booklets of tree sur-
geons, once said to the author, who was in the act
of painting with tar an incision in an apple-tree,
" I suppose that the apples will taste of tar for a
year or two, won't they?" When these ideas
become a little more widely disseminated it is
to be expected that progressive growers will be
found pouring liberal doses of " Red-eye " into
holes in their apple trees, by way of preparation
for marketing their fruit in the prohibition States.
It cannot be too emphatically stated that no
cement filling, nor any other filling, nor the re-
moval of decay that precedes the filling, can have
any physiologically beneficial effects upon the tree.
Decay is harmful in exactly the same way that a
hole cut in the tree with an ax is harmful. It
interrupts, in proportion to its extent, the exchange
of sap between the roots and the leaves, and it
removes a certain part of the physical support of
the tree. It is to prevent the increase of these
very dangerous processes that the decay is cut out.
But the excision does not, obviously, remedy the
harm which has already been done. Indeed, it
actually increases the damage to the tree, for the
hole is always larger than the decay-spot it was
made to eradicate. If better foliage sometimes fol-
lows the putting in of fillings, it is because the trees
are often pruned severely at the time they are
filled. No real advance in the work of repairing

98 PRACTICAL TREE REPAIR

decaying trees can be made until this lumber of
false notions is cleared away, and the real value
of the work is studied and determined.

With this analysis of the purposes of tree fill-
ing in mind, let us pass now to a brief inventory of
the different types of cavities, making an effort to
estimate, in each case, the probability of a suc-
cessful realization of these purposes.

The smaller holes in trees, caused by weather-
ing and local or incipient decay starting from a
decaying stub or a bark wound, can often be very
rapidly and completely cleaned of rotten wood.
The cavities can usually be well drained and not
only are the fillings easily waterproofed, but they
are likely to be callused over within a reasonable
time. If properly done such fillings are almost
sure to be wholly successful. They are of great
importance in preventing the spread of decay and
the formation of cavities more difficult to treat.
No hesitancy should be felt in putting such work
into trees of even secondary importance, or into
orchard trees whose value is strictly commercial.

Next in the scale of simplicity are moderately de-
veloped basal cavities — rotting places, that is, at
the base of the trunk. If in handling such cavities
it is possible to remove all decay and to " ground "
the filling, the work is sure to be effective and
profitable. The rot which was gradually weaken-
ing the tree has been permanently eliminated.

A tree that

FILLING TREES 99

Danger from water pockets, the most frequent
cause of failure in tree work, has been completely
avoided by the good drainage produced by
grounding the filling.

In basal cavities which have progressed farther,
the decay working higher up the trunk, some of
those advantages may be realized which follow
the filling of simpler cavities of the same type,
while others may not be. The main difficulty is in
the removal of all the decay, especially when it
runs higher up in the trunk and perhaps into
several large limbs. In such a case the larger ex-
pense and the greater uncertainty as to effective-
ness demand that careful consideration be given
to the value of the damaged tree and to its possible
future value, before the work is started.

When we come to large cavities in the upper
part of the trunk, oftenest caused by the break-
ing out of large limbs, involving bad crotches and
saddles, we come to the most difficult and most un-
certain class of cavity work. The trees are often
so old that their value is problematical at best.
The great strain on the filling makes indispensable
a great deal of expensive bolting through the
trunk, with its unavoidable damage to the conti-
nuity of the cambium. It can be pretty definitely
stated that fillings of this type cannot be done suc-
cessfully with concrete. Such a filling has to be
divided into small sections to accommodate the

ioo PRACTICAL TREE REPAIR

inevitable swaying and twisting. The divisions
between the sections are certain, sooner or later,
to admit water, and calluses will not grow over a
filling which grinds against them in a wind. For
such cavities as this, asphalt is now being advocated
as a filling, but none of the different methods of
using it has been tried out long enough to make
its value absolutely certain. No large job of this
kind should be undertaken unless the probability
of large expense, and the possibility of ultimate
failure are squarely recognized.

In this connection it may be note4 that when
the tree surgery companies publish photographs il-
lustrating their largest jobs, the pictures are always
observed to have been taken during the progress
of the job or immediately upon its completion.
When, however, they print pictures taken several
years after the work is done (as in showing callus
growth, which is supposed to be proof of success)
the pictures are almost invariably of simple basal
fillings.

By keeping in mind this scale, indicating roughly
the relative costs and risks of the different classes
of fillings, and also the preceding list of " don'ts "
relative to expensive fillings in trees, it is possible
for the owner of trees, or his adviser, to arrive at
a pretty definite conclusion as to whether to order
his decayed trees filled or not.

In view of what has already been said, it is

FILLING TREES 101

hardly necessary to insist that it is impossible to
answer with one word the question " Is filling
trees successful?" It all depends on the tree,
the cavity, and the filling. A small cavity in a
healthy tree can be filled with certainty of success.
A large and complex filling in a decrepit tree may
well be beyond the power of any man to accom-
plish successfully at any cost. Somewhere between
these limits lies the line of demarcation, fluctuat-
ing with the existing conditions and the skill of the
workman. Further observations on old jobs may
draw that line farther back toward the simple
operations. Future inventions and greater skill
may push the line out to a point where it will in-
clude more difficult work than has yet been at-
tempted. The rules laid down in this chapter aim
to locate the line as definitely as that can now be
done.

In conclusion, for the sake of the emphasis which
comes of repetition, let it be said again here, as it
has already been said several times in various
forms, that tree surgery is not nearly so important
to trees as feeding, watering, and spraying, and
that the common-sense, as well as the scientific
procedure, is first to make the tree vigorous, and
then, if it needs filling, to fill it.

CHAPTER VII

THE FILLING OF CAVITIES —
MATERIALS AND TOOLS

THE treatment of cavities is the part of tree
repair which presents the greatest technical
difficulties, as well as the largest opportunities for
the application of the principles of the nature and
growth of trees and of the spread of decay. The
causes of cavities in trees have already been
stated. The many ways in which they are dan-
gerous have also been touched on in several con-
nections. Perhaps the clearest way to state the
potential peril which lies in every cavity is to say
that all cavities grow. Slowly, but steadily, every
cavity grows larger and larger, until the exchange
of sap between roots and leaves is so far cut off
that the tree dies, or until the supporting frame-
work of the tree is so far eaten away that the tree
is broken down by the wind. Every cavity is
therefore a stage in the steady course from the
bark wound to the hollow, shattered tree. Other
factors may bring about the death of the tree be-
fore the cavity gets in its work, but the cavity is

102

FILLING OF CAVITIES 103

always at least a potential cause of the tree's
destruction.

It is no wonder, then, that heroic measures are
often resorted to in order to stop the spread of
a cavity. For, as the essential reason why they
must be treated is that all cavities grow, so the es-
sential principle of their treatment is to stop their
growth. And, conversely, the degree to which
a treatment is successful is the degree to which the
growth of the cavity has been stopped. Although
the essential idea in the treatment of cavities is to
stop their growth, other principles are involved,
which, though not primary, are by no means with-
out importance. These are that the treatment
must be such as to facilitate the healing over of
the interruptions in the continuity of the bark
which accompany wounds and cavities, and, in so
far as possible, it should be such as to restore to
the tree the strength which has been taken from it
by the destruction of its tissues. The first of these
is in one way a corollary to the principle first
stated, that of stopping growth, because the heal-
ing over of a wound is the surest way to prevent
reinfection.

The ways in which these principles are put into
practice will appear later, but it may be well to lay
down at this point a skeleton program of the dif-
ferent processes which are normally included in a
complete cavity treatment:

104 PRACTICAL TREE REPAIR

1. The decaying wood is completely removed,
the mouth of the cavity being enlarged as much
as may be necessary to accomplish this.

2. The mouth of the cavity is so shaped as to
insure a proper retention of the filling, and as to
facilitate the healing of the wound.

3. Braces are put in to strengthen the tree, re-
tain the filling, and prevent the opening of cracks
around it.

4. The interior of the cleaned cavity is treated
and dressed in such a way as to prevent the rein-
fection of the wood by fungi, and, in so far as is
possible, to produce a water-tight connection be-
tween the filling and the wood.

5. The cavity is filled, care being taken that the
surface of the filling is so arranged as not to inter-
fere with the natural healing of the wound.

6. The surface of the filling is so treated as
to make it water proof.

This outline may help to give unity to the rather
piecemeal handling of the subject-matter of the
chapter which is unavoidable from this point on.
We shall first discuss the tools which are used in
this branch of tree repair, then the materials, and,
finally the methods.

TOOLS

The tools used in cavity work are those nat-
urally suggested by the kind of work to be done.

FILLING OF CAVITIES 105

In clearing away the dead wood, the main re-
liance is placed upon carpenters' gouges of the
larger sizes, inch-and-a-half being perhaps the
most useful size, while the two-inch size makes fast
work if the wood is soft. Smaller sizes also have
their special uses. It is hardly necessary to say that
the gouges are outside-ground and socket-handled.
This last feature is important on account of the
frequency with which the handles break and have
to be replaced. The best handles are made of
sound ash or hickory, and are fairly large, with
an iron ring around the butt. For work in large
cavities long handles have to be fitted to the
gouges. Old wagon spokes are the best stuff to
use for this purpose. They can usually be got for
nothing at any blacksmith's. The butts will have
to be strengthened with an iron ring or the spokes
will soon split. If these rings cannot be bought
at the local hardware or department store sub-
stitutes can be made by sawing a gas-pipe into inch
lengths.

Mallets, the invariable companions of the
gouges, also come in several sizes and styles.
Those of lignum vita usually last longest, but
the wear and tear on them is very great, and a
mallet which has a crack in it will not last long.
Tastes differ as to weight of head and length of
handle, but fast work cannot be done with a light
mallet. The writer prefers the size known as

io6 PRACTICAL TREE REPAIR

number eleven (weighing a little less than two
pounds), and a handle about ten inches long.

After these tools, perhaps the most useful is a
light hand ax, especially in large work. An adz
is also very useful, as is a pruning saw of the
" meat-saw " type, the blade of which can be set
at right angles to the handle, making it a handy
tool when there is a large " lip " to be cut from the
edge of a cavity.

Several more or less successful efforts have been
made to devise machines for excavating decayed
wood. As yet none of these has come into general
use, the extremely variable conditions presented by
work in trees giving human labor a peculiar ad-
vantage over the less easily controlled mechanical
devices.

Under the head of tools ought also to be men-
tioned the ladders necessary for getting at the cavi-
ties to be excavated when they are high above
ground. The devices used, the various combina-
tions of ladders, step-ladders, planks, and ropes
which are made for the purpose of securing a com-
fortable footing while at work, are endless. The
work to be done and the materials at hand with
which to do it will suggest to a handy man the best
arrangements which can be made under the exist-
ing circumstances. It saves time to make the con-
ditions of work in each case as comfortable as pos-
sible.

FILLING OF CAVITIES 107

MATERIALS

Dressings. — It is natural, when the materials
employed in the treatment of cavities are men-
tioned, to think first of concrete and the like. But
of first importance are the dressings used on the in-
terior of the cavity before the filling is put in.
Logically, those materials are practically the same
as the materials used for wound dressings, a sub-
ject considered at length in a previous chapter.

The materials of greatest value as dressings for
cavities are creosote, the best preliminary disin-
fectant and preservative; coal tar, mainly of value
when the cavity is dry and well-drained, and the
various forms of fluxed asphalt.

Fillings. — A large number of different materials
have been or are being used for filling trees. Con-
crete is of course the commonest of them. Lately,
asphalt has been supplanting concrete for many
kinds of work. In the present division of the
chapter the principal materials and the ways in
which they are prepared for use will be discussed,
leaving for a later division an account of how they
are put into the tree.

Concrete. — Cement is a fairly easy material to
handle. Any one can mix up a pail of cement with
a wheelbarrow or two of gravel, pour it into a soap
box, and make a passable horse-block. But the
ease with which a certain kind of success is attained

io8 PRACTICAL TREE REPAIR

with cement is apt to lead to ineffective results
when the work is subjected to conditions at all try-
ing. A person who wants to do good work with
cement, work suited to the materials used and
adapted to the end aimed at, must make himself
familiar with the properties of cement and of con-
crete and with the principles governing the selec-
tion of materials entering into the concrete, the
mixing of those materials, and the placing and
hardening of the mixture. There is a number of
cheap and excellent handbooks dealing with these
matters, and one of them should be familiar to
every user of cement. In this book, however,
only the elements can be presented, and such de-
tails as bear directly on the use of concrete as a
filling for trees.

It may be well to begin with a few definitions.
Concrete is an artificial stone made up of small
pieces of natural stone held together by a matrix
produced by the crystallization of hydraulic ce-
ment and water. The materials held together,
such as sand, gravel, or broken stone, are called
the aggregates. Portland cement, the hydraulic
cement commonly used for making concrete, con-
tains lime, silica, alumina, and other elements, and
is made by melting a limy substance with a clayey
substance and grinding the resultant clinker to a
very fine powder. It is this material alone which
is correctly called cement, the mixture of it with

FILLING OF CAVITIES 109

water and any form of aggregate being concrete.
The word cement is, however, frequently used to
designate concrete, especially when the aggregates
employed are small.

Concrete, then, is made by mixing cement with
aggregates and with water. In order that the
concrete may be good the materials of which it is
made must be carefully selected. Portland ce-
ment is very uniform and it is safe to use the prod-
uct of any of the large mills, or any brand sold
by a reliable dealer. If kept for any length of
time it must be protected from moisture, and must
be dry and powdery when used. It comes in
paper or cloth sacks containing about ninety-five
pounds. Four sacks make a barrel and cost about
a dollar and a half.

The aggregates present greater difficulties. In
the first place, the type of aggregate best suited to
the purpose must be determined. It has been the
usual custom to employ simply a mixture of cement
and sand for filling trees, on account of the fact
that coarser aggregates make it difficult to work
the exposed surface of the filling down smooth.
A concrete made of small aggregates, however, is
not so strong nor so dense as one in which larger
aggregates are used. W. A. Radford, in
" Cement and How to Use It," makes a clear
statement of this principle:

" There is the closest relation between the

i io PRACTICAL TREE REPAIR

density and the strength 'of concrete. Even a
slight increase in weight per cubic foot will add
very decidedly to the strength. In this connec-
tion the importance of the coarser aggregates can-
not be too strongly insisted upon. The use of
coarse material is essential to density, since coarse
material contains the smallest amount of voids.
Different kinds of sand, gravel, and stone vary
greatly in the amount of their voids; and by judi-
ciously mixing coarse and fine materials, the
voids may be much reduced, and the weight and
density of the concrete increased.

" If the sand be screened so as to take out the
coarse grains, the voids will be increased and the
weight reduced, thus injuring the sand for making
concrete. Strength may be improved by adding
coarse material, even though the proportion of
cement is thereby reduced. This has been re-
peatedly shown by experiment. A mixture of
cement and sand alone will form a rather weak
concrete, especially if the sand is fine. By adding
gravel — say about twice the quantity of gravel
that there is of sand, or a little more — a con-
crete will be obtained containing, of course, a
greatly reduced percentage of cement, but of
greatly increased strength."

The strain on concrete fillings in trees is so great
that a sacrifice of strength for a fancied esthetic
effect is not easily justified. It is, moreover, not

FILLING OF CAVITIES in

difficult to handle a rather coarse aggregate in such
a way as to make a fairly smooth surface, espe-
cially if that surface is given a heavy waterproof
dressing. Placing, as he does, efficiency before
appearance, the writer urges the use of larger
aggregates in making concrete for filling trees.
Half-inch crushed stone makes an excellent
material for the purpose, as also does screened
gravel.

The selection and proportioning of the aggre-
gates depend upon the principle that the most com-
pact and strongest concrete is made by so grading
the aggregates that the mixture may contain a
minimum percentage of voids. Enough cement
is mixed in to fill the voids, and the resultant con-
crete is practically solid. An ideal combination
of aggregates, therefore, is one which brings to-
gether fine and coarse sand, small stones and large
ones. A mixture of sand with screened gravel or
broken stone conforms fairly closely to this ideal,
as, to a slightly less degree, does bank gravel, a
natural mixture of sand and gravel.

Good sand is fairly coarse, with grains of grad-
uated sizes, and, above all, it must be clean. A
coarse mixed sand requires less cement than a fine,
uniform one. Besides the dead and dusty appear-
ance of dirty sand when it is dry, the following
test for fresh sand is very useful. The descrip-
tion of it is quoted from " Concrete Construction

ii2 PRACTICAL TREE REPAIR

About the Home and on the Farm," published by
a cement company.

" Pick up a double handful of moist sand from
the bank; open the hands, holding them with the
thumbs up ; rub the sand lightly between the hands,
keeping them about half an inch apart, allowing
the sand to slip quickly between them. Repeat
this operation five or six times, then rub the hands
lightly together so as to remove the fine grains of
sand which adhere to them, and examine to see
whether or not a thin film of sticky matter adheres
to the fingers; if so, do not use the sand, for it con-
tains loam."

Bank gravel makes a fairly good ready-mixed
aggregate for concrete, although as a usual thing
it is not correctly proportioned, the amount of
sand being excessive. It is ordinarily best to put
some of the gravel through a quarter-inch screen
in order to determine what its actual composition
is. Then, if a deficiency of the larger pebbles is
indicated, enough screened gravel can be added to
make, the proportions correct. If pure sand has to
be used it must be mixed at about the rate of two
parts of sand to one of cement, in order to approxi-
mate the richness of a 1 14 gravel mixture.

The various mixtures of cement, aggregates,
and water, which are used in making concrete are
grouped in two ways : according to the proportion
of cement to aggregates, and according to the

FILLING OF CAVITIES 113

amount of water incorporated in the mixture. A
rich mix is one in which one part (by loose bulk)
of cement is mixed with two parts of sand and
three of gravel. A medium mixture runs about
1:3:6, and a lean mixture, 1:4:8. Arranged ac-
cording to wetness, a very wet mixture is one
which is mushy enough to run off the shovel, a
medium mixture is jelly-like and will quake on
tamping, while a dry mixture closely resembles
damp earth.

For filling trees a rich mixture should ordinarily
be employed, because the actual amount of cement
used is small and because it is highly desirable that
the filling set quickly and become very hard. In
positions where there is but little strain on the fill-
ing, as beneath or near the surface of the soil, or
in a large cavity with a small opening, a mixture
of medium richness can be used with entire safety.

The degree of wetness is not so easily disposed
of. For the most part a rather dry mixture has
been used for filling trees. The difficulty of mak-
ing a form into which to deposit the concrete al-
most compels the workman to use a mixture so
dry that he can build it up without a form and
without danger of its slumping down through the
opening of the cavity. This is the easiest way to
put in a concrete filling, and it has been almost
the universal way. It is constantly being made
clearer and clearer, however, that the dry system

n4 PRACTICAL TREE REPAIR

is subject to one very serious danger. Many fill-
ings made in this way, though they may at first
seem hard, gradually " rot." The writer believes
that the explanation of this difficulty lies in the
dryness of the mixture. There is a saying that
a wet mixture tamps itself, but that a dry mixture
must be tamped. A dry mixture which is not
thoroughly tamped cannot make a dense concrete.
Now it is almost impossible to tamp properly con-
crete which is being built up in a cavity. In the
first place, there is not often much elbow-room
and it is difficult to apply sufficient force. Then,
too, a hearty ramming would almost surely cause
the lower part of the filling to belly out or to fall
out bodily. As a result, tree fillings are not often
tamped with anywhere near the force considered
essential in the manufacture of building blocks by
the " dry method," which is practically the only
large use of dry concrete. Such fillings are in-
evitably porous, and porous concrete is like a
sponge. If there is any water about, the concrete
will absorb it.

This brings us to another difficulty which often
arises in connection with dry fillings. It often
happens that a large part of what water there is
in the mixture evaporates the very first day it is
in place. Between this evaporation and the orig-
inal scantiness of water, not enough is left to crys-
tallize the cement in the concrete. When the con-

fin

Cavity in the base of a white oak filled with concrete

FILLING OF CAVITIES 115

crete dries out only a part of the cement really
hardens. The rest, although its cementing value
is destroyed, does not harden and is left in the
concrete in an unfixed condition. Now when this
concrete becomes saturated with water, and the
water works downward and out of any drainage
openings which may occur, it carries with it some
of this loose cement, a condition of things which
is betrayed by a light-colored stain on the bark
below the opening of the cavity. As this process
goes on the porousness of the concrete must ob-
viously increase, and before long the filling is ab-
solutely saturated, and has become rotten, friable,
and weak. This result is the more surprising be-
cause a week after the filling is put in it usually
seems as hard as flint, due to the fact that trowel-
ing and smoothing the surface draws to it a large
ampunt of cement and water, which cause the sur-
face of the filling to become really hard.

As a remedy for this state of affairs two solu-
tions have been tried. The old method has been
rid of some of its faults by making the mixture
just as wet as it is possible to handle it, by paying
greater attention to the tamping, and, especially,
by preventing the access of water to the concrete
by means of improved dressings for the inner sur-
face of the cavity and the outer surface of the
filling. At the same time, efforts have been made
to find a practical means of handling a wet mix-

n6 PRACTICAL TREE REPAIR

ture, for therein lies the real solution of the prob-
lem. The writer has tried several schemes to
overcome the mechanical difficulties presented by
the wet mixture. The most successful of them,
and also the best way of handling the dry mixture,
will be described later under the general descrip-
tion of the method of filling cavities.

Little need be said concerning the details of
mixing concrete and the like, for such matters are
familiar to almost every one, and they are de-
scribed fully in pamphlets which can be secured
free of charge from the Government or the manu-
facturers, and in cheap and easily obtainable hand-
books.

Something ought, however, to be said about
quantities and costs. As soon as a job has pro-
gressed far enough to make possible an estimate
of the cubical contents of the cavity, the amount of
materials required to fill it should be figured out
and provision made for obtaining them. To do
this it is necessary to know how much cement and
aggregates is needed to make a certain amount
of concrete. Suppose the aggregate is a natural
mixture of sand and gravel. It will be a little
shy of gravel and the mixed sizes will not bulk as
large as if they were separated, so you will have
to use one part of cement to four parts of gravel
to make the equivalent of a i :2 14 concrete. At
the rate of one to four, a bag of cement, three and

FILLING OF CAVITIES 117

three-quarters cubic feet of gravel, and five gallons
of water will make a medium wet mixture which
will make four and a quarter cubic feet of concrete.
So by dividing the number of cubic feet in the
cavity by 4^4 you can obtain the number of bags
of cement to order, and by multiplying the num-
ber of bags of cement by 3J4, you can obtain the
number of cubic feet of gravel required. If the
sand and stone or gravel are secured separately,
the amounts required can be calculated from the
proportions of the ingredients of a cubic foot of
concrete. A cubic foot of i :2 \\ concrete con-
tains approximately .015 of a bag of cement, .016
cubic yard of sand, and .032 cubic yard of stone or
gravel.

The cost of materials varies greatly in different
parts of the country, but a fair average would be
$1.50 a barrel for cement, $.80 a yard for sand,
and $1.20 for stone. A combination of these fig-
ures with those above indicates that a cubic foot of
1:2:4 concrete contains $.056 worth of cement,
$.013 of sand, and $.04 worth of stone, making
the cubic foot cost, for materials, approximately
eleven cents. • It is more likely to exceed than not
to reach that figure.

Asphalt. — It is now generally recognized that
concrete is not fitted to serve as a filling material
for every kind of cavity. With that recognition
has come a demand for a more elastic material,

ii8 PRACTICAL TREE REPAIR

more like wood in its properties, and capable of
becoming more nearly like an integral part of the
tree. The moment this need was stated, asphalt
suggested itself as the material which most nearly
meets the requirements. It is, indeed, practically
the only solid filling material which has been
brought forward as a substitute for concrete. Its
eminent fitness is obvious. It is slightly elastic,
while concrete is absolutely rigid; it is waterproof,
while concrete absorbs water; it adheres to
wood, while concrete does not; it is light and
warm, while concrete is heavy and cold.

In a preceding chapter, under the topic of
wound dressings, some of the various kinds of
asphalt have been mentioned. It cannot as yet be
definitely stated what form of asphalt is best suited
to tree work. For outside waterproofing appli-
cations, the writer is convinced that bituminous
cement made from the natural asphalt is the best.
For cavity work it may sometimes be little more
than a question of choosing the cheapest material,
especially when the metal-front system is used.

Such brief description as is necessary of the
methods of mixing the asphalt with other sub-
stances, in the preparation of the actual filling-ma-
terial, is best deferred until the processes of filling
appropriate to each material are being described.

CHAPTER VIII

GENERAL METHOD OF FILLING
CAVITIES

SO much for the materials used in dressing and
filling cavities. Next in order is a general
description of methods — the way the excavation
is made, the way the hollow trunk is braced and
filled. This general description will be followed
by specific discussions of the various types of
cavities and of the special problems each presents.

PRELIMINARY SURVEY

After it has been decided to fill a cavity in a cer-
tain tree, the first thing to be done is to make a
careful investigation of the decayed portion of the
trunk, the purpose being to map out the course to
be followed in excavating the rotten wood. If
openings already exist, as they usually do, it must
be decided whether they will offer sufficient access
to the decay, and, if not, how much they must be
enlarged, or what new incisions must be made, and
where. It is often wise to leave the cutting of
new holes until after the excavation is well under

119

120 PRACTICAL TREE REPAIR

way, but when the need of them can be clearly
foreseen, it is an economy to cut them at once, so
that each portion of decayed wood can be removed
from the most convenient point. If the decay

Vertical section of a decayed oak, showing holes bored to de-
termine extent of decay, and section of the same tree excavated
and filled

runs down the trunk to the ground on any side,
the soil must be dug away. It may be well to
mention here that cavity work is very hard on the
grass around the tree, and it is often well to lay
down a piece of canvas or burlap, to protect the
sod. Existing openings must in every case be

GENERAL METHODS 121

enlarged to sound wood an inch or so thick, in
order to provide a proper edge for the cavity.
If there are old callus lips rolling over the side of
the opening of the cavity, and there is rot behind
them, they must be cut away. In case new in-
cisions are necessary, they are made, when possi-
ble, at a place where there is already an injury to
the tree, such as a patch of dead bark, or where
the wood is thin and the slow growth of the bark
indicates that the flow of sap will not be seriously
interfered with by an incision. It requires con-
siderable experience to enable a man to say in ad-
vance just how large an opening will be needed
for removing the decayed wood from a cavity,
but to do so often saves much time, for it frequently
happens that a man chips a long time at a patch
of dead wood which could have been very quickly
removed through an opening made later on.

EXCAVATION

The openings once fixed on and made, the work
of removing the rotten wood begins. At first this
is usually easy enough, but it grows harder and
harder as the work progresses. All sorts of
tricks have to be used in order to get at all
of the decay. Sometimes if a gouge won't "bite,"
a chisel, with its edge toward the wood, will
do the work. An extension bit is also very
useful in handling " pockets " of rotten wood.

122 PRACTICAL TREE REPAIR

" Punk- wood " can sometimes be burnt out
with a gasoline torch, using a tree scraper
to scrape off the charred wood and control the
flame.

It would require a good many pages even
to enumerate the hundreds of schemes and adapta-
tions employed by a resourceful workman during
a season's work. A person of normal ingenuity
will not need any further suggestions along this
line than are daily furnished by the work to be
done and the tools at hand.

As the work nears completion, the operator
must constantly keep in mind the standard of per-
fection decided on in the beginning. The tree
has presumably bee,n sounded (by boring holes, if
necessary) , and it has been definitely determined
that all of the decay can and should be removed,
We shall speak later of those cases in which it is
found impossible to get out all the rotten wood.
At present we are taking it for granted that com-
plete excision has been prescribed. It may seem
superfluous to say (but repeated experiences have
shown that it is not) that " complete " does not
mean " substantial." It does not mean that the
rot is to be cleaned away perfectly where it is easy
to get at, and yet permitted to remain in corners
and crotches which are difficult of access. And
too much must not be left for the antiseptic dress-
ing, for few of the dressings soak in to any con-

GENERAL METHODS

123

siderable depth. Half an inch is all that can
usually be counted on.

Aside from the necessity of making sure that
all infested wood is removed, it does not make
much difference in what shape the interior of the
cavity is left. It does not have to be smooth, ex-
cept in so far as may be required by the nature of
the dressing to be used. Tar, for instance, will
not flow behind large semi-detached chips, but as-
phalt may cover them easily.

SHAPING THE MOUTH

The excavation finished, the next step is the
proper outlining and edging of the opening. The
mouth of the cavity
must be so shaped that
the filling will be re-
tained, the formation
and growth of calluses
facilitated, and the en-
trance of water into
the cavity made unlikely.
The first purpose is at-
tained by making the
cavity larger back of the
mouth than it is just at
the mouth. The entrance of water is made less
easy by slanting upward the upper and lower
edges of the opening, so as to form water-sheds.

Vertical section showing top
and bottom of cavity slant-
ed up to prevent entrance
of water

If the top of the incision is
made too square callus
growth does not start from
the top

124 PRACTICAL TREE REPAIR

As regards the encouragement of calluses, the im-
portant thing is to keep in mind the facts and
rules concerning the cambium and the growth of
calluses which have been explained in the chapter
on the nature of tree growth. The mouth of the
cavity should be kept as narrow as possible, the
sides fairly straight and parallel to the strong-
growing ridges of the trunk, and the ends of the

Cross sections of four incorrect fillings. In the first, the exca-
vation is not correctly shaped for retaining the filling; in the
second, the filling is brought out so far that the cambium
cannot spread over it; in the third, the filling bulges too
much; in the last, the wood at each side of the opening is
cut too thin

opening should be tapered. Some otherwise skil-
ful operators cut the top of the opening off square.
That is a mistake, for if the tree is growing very
slowly a triangular-shaped piece of bark just
above the filling either dies or makes very slight
growth, thus forming an ideal haven for boring
insects. To avoid the possibility of the cam-
bium's drying out, there must be a reasonable
thickness of sap-wood beneath it, which means
that very thin lips should be cut back to a point
where the wood is an inch, say, in thickness. In

GENERAL METHODS 125

this connection it may be noticed that there is
always danger, especially when the bark is thin,
that the cambium will be killed by drying back
an inch or so from the edge of the opening.
This amounts to an enlargement, by so much, of
the wound, and measures should be taken to pre-
vent it. If the job lasts several days, the tempo-
rary edge of the opening should be shellacked if
the danger is considered sufficient to warrant the
trouble. When the edges have finally been
shaped and pared smooth, the bast and cambium
and the wood an inch below it should be painted
with shellac or liquid wax. Such treatment will
not only prevent drying but also the killing of
the cambium by the antiseptic dressing.

BRACING

Bracing is next. Braces are put in to
strengthen the tree, to make it more nearly rigid,
in order that it may not crush the filling, to assist
in the retention of the filling, and to prevent the
opening up of cracks around its edges. For all
these purposes it is almost futile to try to use
braces which are entirely within the cavity. Such
braces cannot be made stiff enough, and cannot be
anchored strongly enough to the wood. The only
way to do is to run the braces clean through from
one side of the trunk to the other, which of course
means that ordinary machine bolts are exactly

126 PRACTICAL TREE REPAIR

suited to the purpose. The number of bolts de-
pends upon the size of the tree, the thickness of
the sound wood, and the number and size of the
openings of the cavity. As the most common
function of the braces is to prevent the formation
of cracks around the filling, they are usually in-
serted as close to the mouth of the cavity as pos-
sible, reminding one of the stitches with which a
surgeon closes up a wound. It is not often that
the bolts need be closer together than eighteen
inches. The diameter of the bolts should be kept
down to the minimum of safety, not only to save on
the cost of the iron, but also to avoid making un-
necessarily large holes in the bark in inserting them.
Considering that the steel of which machine bolts
are made has a strength of fifty thousand pounds
to the square inch, it is evident that anything
larger than five-eighths bolts will not often be
needed. Bolts in trees give way, when they do,
by snapping off, or pulling out of, their heads.
When ordering special sizes and extra lengths from
the blacksmith the best way is to have both ends
of the bolt threaded. A nut can be set on one
end and can be considered as a head, or both nuts
can be used to tighten up the bolt.

In case the slope of the bark toward the mouth
of the cavity is such that a large socket would have
to be cut in order to form level floors for the head
of the bolt and the nut, it is better to run them

GENERAL METHODS

127

Beech tree with old trunk cavity and the same tree, excavated,
braced, and filled with asphalt

through the center of the tree, only one end being
near the edge of the cavity. The same method
is advisable when the wood on either side of the
cavity is very thin. After the location of the bolts
is decided on, the holes for them should be bored,

128 PRACTICAL TREE REPAIR

the sockets cut out or bored out with a large
auger and measurements for the bolts made.
These processes will be described at greater length
in the chapter devoted to the bracing of limbs.
Every effort should be made to keep the sockets
as small as possible. Nor need they be cut much
deeper than the cambium. Large, deep sockets,

Cross sections showing two ways of Sockets for bolts, one too
bracing a cavity deep, the other correct

in which the bolt head can be completely covered
with cement, may look better to some people than
smaller ones, but in them appearance is gained
at the cost of lessened strength in the brace and
greater damage to the tree. It is hardly neces-
sary to say that the sockets and the bolts must be
painted with some disinfectant, such as tar, before
the bolt is inserted.

These bolts do riot usually strengthen the tree
to any great extent. There are a number of sys-
tems of bracing in common use which are claimed
to strengthen the tree. In the writer's opinion
they do not often materially do so. In one sys-

GENERAL METHODS 129

tern a network of strap-iron, elaborately bolted to-
gether, is staggered back and forth inside the tree.
But the reinforcing elements are so short and weak
in comparison with the leverage of the limbs and
the power of the wind, that it is difficult to believe
that they have any substantial strengthening value.
Another method is to reinforce the concrete with
rods of steel, just as structural concrete is rein-
forced. This can only be of value when it is used
in a long cavity which is decidedly more weaken-
ing in the middle than it is at either end. If the
tree is weakest at the ground this system would
increase the danger because it would destroy the
shock-absorbing capacity of the trunk and make
of it a lever by which the top could bear on the
lowest part of the trunk. Doubtless these and
similar systems of interior bracing have occasional
uses, but before going to much expense in that
direction it is a good idea to make a diagram of
the proposed reinforcements and submit it to a
civil or structural engineer. If his discussion of
the project leaves you convinced of its value, go
ahead.

In the case of a tree so far gone as to suggest
such elaborate interior reinforcement, it will
usually be best to employ the " open system " of
cavity treatment which will be described in another
chapter. Strengthen the weak limbs with outside
braces. If possible, strengthen the whole tree by

130 PRACTICAL TREE REPAIR

running wire ropes to it from its sturdier neigh-
bors. These braces need not be conspicuous.
Their strength is not problematical : it can be cal-
culated to the pound. Plant a Virginia creeper
or Euonymus radicans at the base of the old tree
and spend the money you have saved in setting
out a young one.

DRESSING THE CAVITY

The braces in place and tightened up, the next
thing on the program is the antiseptic treatment
of the interior of the cavity. The materials suit-
able for this purpose have already been enumer-
ated. The choice of a material or a combination
of materials depends upon the completeness with
which it was possible to remove the decay, the con-
dition of the exposed wood, and the shape of the
cavity, and the material to be used in filling. If
a penetrating antiseptic is needed, carbolineum is
the most effective. If the wood exposed in exca-
vating is damp it is essential that it be allowed to
dry for a few days, the cambium, of course, being
protected. It does no harm for a cavity to stand
in this way half the summer. If time for natural
drying is not available, the cavity can be dried out
fairly well with a gasoline torch, though consider-
able discretion is needed in the use of that tool.
A cavity which is to be filled with concrete should
never receive, as its final dressing, any material

GENERAL METHODS 131

less heavy than asphalt, unless it is a perfectly
drained basal cavity, in which case coal tar can be
used. Whatever material is chosen, it must be
applied after the braces are in, and the applica-
tion must be thorough and absolutely complete.

FUMIGATING

If boring insects have gained entrance through
the trunk, and have progressed beyond the decay,
so that some remain after the decay is removed,
the cavity must be fumigated before it is filled.
Tack a sheet of tar-paper over the mouth of the
cavity, filling the interstices between the paper and
the bark with clay or cotton-batting dipped in mud.
Just before the last corner is packed down throw
in a rag soaked with a teaspoonful of carbon bi-
sulphide for each cubic foot of space in the cavity.
If the cover is tight the larvae will be dead in a
few hours.

FILLING: CHOICE OF MATERIAL

The cavity is now ready for filling. The first
question in that connection is the choice of a filling
material. Concrete is still generally looked upon
as probably the best filler for the more simple
types of cavities, although its shortcomings and
limitations are constantly being more widely recog-
nized. Its advantages are that it is very cheap, is
easily obtainable everywhere, requires none but

132 PRACTICAL TREE REPAIR

common tools and appliances, and is easily and
quickly put into the tree. On the other hand, it is
absolutely unlike wood in all its properties, being
heavy, cold and rigid, while wood is light, warm
and elastic. It is very difficult to get a good junc-
tion between wood and cement. Cement is always
somewhat porous, and usually damp, and attracts
and condenses moisture, the greatest enemy of the
life of wood. It is very weak when it is new,
and is then and later frequently crushed by the
immense strength of a bending and twisting tree.
Almost the only thing in its favor is its conveni-
ence. Many situations and conditions, however,
can be found in which the drawbacks of concrete
are minimized in importance, and in which it is
as good a material as any.

Perhaps an attempt to lay down certain rules
covering these points would be worth while: In
basal cavities which are well grounded and which
do not extend up into the trunk a distance greater
than two or three times its diameter, use concrete.
In small cavities, at least so small in relation to
the size of the trunk in which they occur that when
the tree sways they move as a unit and do not vary
much in shape, use concrete if the wood is dry.
When the conditions are slightly more severe than
these, concrete can often be used with safety, pro-
vided extreme care is taken with the braces, the
dressing of the cavity, and the covering of the sur-

GENERAL METHODS

face of the concrete. If the drainage is poor, if
there are many openings, if the tree twists and
bends in the wind, use asphalt. These rules gov-
ern fillings only. In a succeeding chapter will be
found accounts of cavity treatments which do not

The two trees at the left are proper subjects for cement fill-
ings. Those at the right must be filled with asphalt or
treated by the open system, without fillings

involve filling, and also discussions of the value
and proper use of each.

Coming now to the actual operations of putting
in the filling, the methods of handling concrete
will be described first — then the use of asphalt.

FILLING WITH CONCRETE

Concrete fillings can be put into trees in a num-
ber of different ways. And the differences, though

i34 PRACTICAL TREE REPAIR

at first glance they may seem of slight importance,
are not so much differences of method as they are
differences of purpose. In other words, the men
who have developed the different systems, have
had different ideas as to the function of cement
fillings. In the early days of cement work in
trees, it seems to have been taken for granted that
the main value of the filling lay in its strengthen-
ing effect. The question of how this supposed
effect was brought about does not seem to have
been asked. It simply " seemed natural " that a
tree which was full of hard cement should be
stronger than a hollow tree. However, when
irregular cracks appeared across the face of every
large cement filling, and when the filled trees
proved to be no more resistant to storms, appar-
ently, than unfilled trees, tree-men began to ask
themselves whether they were working on the
right principle. The idea that the cement was
of considerable strengthening value was not
abandoned, however, and the difficulties which had
developed were explained as being due to the
absence of a sufficiently close bond between the
concrete and the wood. The most obvious
remedy for the trouble was to drive a lot of nails
into the inner surface of the cavity. But the
cracks still appeared. Continuing the same line
of attack, an elaborate system of interior bracing
or reinforcing was developed. This was an im-

Linden on Boston Common, excavated and bolted,
ready for filling

GENERAL METHODS 135

provement on the simple cement filling, but its re-
sults were at best uncertain, and embarrassing
fractures continued to appear in fillings of any
considerable size.

About this time (1907) the writer had to take
out a number of concrete fillings, some eight or
ten years old, which, though otherwise well done,
had been put in without previously treating in any
way the inner surface of the excavated cavity.
He observed, though hardly with surprise, that
while the concrete was perfectly hard and sound,
it was divided into sections, in every situation ex-
cept the very base of a grounded filling, by roughly
horizontal fractures. Many of these cracks were
so small that they could hardly be detected on
the surface of the concrete. These observations
made it quite apparent that it is idle to try
to increase the strength of a hollow trunk by filling
it with a rigid back-bone of concrete. And a little
consideration will make evident the soundness of
this conclusion. The secret of the great strength
of wood lies mainly in its elasticity, the ease with
which it can be bent and twisted. Concrete is
strong in quite a different way. It is almost per-
fectly rigid and inelastic. And it is futile to try
to reinforce an elastic substance with an inelastic
one. Suppose we have two beams, one of con-
crete and one of wood, bridging a certain space.
Suppose the concrete beam has a breaking point

136 PRACTICAL TREE REPAIR

of one thousand pounds, and that the wood will
support the same weight, but that it bends three
inches in doing so. If the beams are placed to-
gether and a weight of twelve hundred pounds is
placed across them, what happens? The wood
begins to bend, but it will hardly be supporting a
hundred pounds before the concrete beam's limit
of elasticity has been reached. The load on it
being in excess of its strength, the concrete breaks,
and the whole load falling on to the wood, it also
gives way.

The importance of this difference in the char-
acter of the strength of the two materials is espe-
cially great just at the time the filling is put into
the tree. It is well known that concrete, though
it hardens with considerable rapidity, does not at-
tain to its ultimate strength for a rather long
period after it sets. It is this fact which explains
the provision in all building codes to the effect that
the forms must be left on structural concrete work
at least two weeks. During the first day or two
that the concrete is in place its tensile strength is
very slight, even though the surface of it may
seem quite hard. And it is absolutely inelastic.
During this first day or two, however, the tree
is certain to sway a little, and if there is much
wind its trunk will be in motion from top to bot-
tom. It is almost impossible to brace a tree so
that it cannot bend, and it is quite impossible to

GENERAL METHODS 137

brace it so that it cannot twist, and the raw con-
crete is just as weak under torsion as it is under
tension. As an inevitable result minute fractures
are produced in the filling, which forever destroy
its tensile strength. It may be said that the con-
crete at least retains its compressive strength, and
that it acts as a buttress to the tree. An architect
might answer that a shallow buttress offers but
little resistance to a horizontal stress, and a num-
ber of instances have come to the writer's notice
in which the filling seemed to act as a fulcrum in-
stead of a buttress, and actually helped to over-
turn the tree. Furthermore, trees are twisted off
more often than they are blown straight over, and
a concrete filling cannot offer much resistance to a
twisting force.

All these considerations compel the conclusion
that the idea that a concrete filling appreciably
strengthens a tree is a mistaken one. What, then,
is the true function of the filling? That function
is threefold. The filling keeps insects, fungi, and
water from gaining access to the heart of the tree;
it forms a surface across which the calluses can
grow, a growth which aids the tree physically and
physiologically; and it probably has some value
in preventing the collapse under strain of a hollow
trunk, a value due entirely to its power of resist-
ing compression.

The effect of this change in the purpose of fill-

i38 PRACTICAL TREE REPAIR

ing is to make a fundamental difference in the tech-
nique of filling. It means that all effort to secure
vertical rigidity can be abandoned. It means that
a filling made up of horizontal layers will perform
all the real functions of a filling, while at the same
time it will control the formation of the inevitable
cracks in the concrete. The " layer system " has
been adopted by most tree repair men, although
not always with a complete realization of the full
significance of the principles which underlie it.

Justice demands that it be said, however, that
in this branch of tree repair, as in most arts and
sciences, there are two schools. Some arbori-
culturists still insist that the right way is to secure
perfect rigidity throughout the concrete filling and
perfect adhesion of the filling to the trunk. To
the multitude of nails and numerous iron braces
once generally in vogue, this school has added an
intricate wire web, woven back and forth across
the opening of the cavity, and fixed to the wood
by a row of staples an inch or so inside of the
cambium. Even though these efforts are success-
ful in accomplishing their purpose, it is a matter
of considerable doubt with the writer whether that
purpose is worth accomplishing. Even granting
that the filled portion of the trunk can be made
perfectly rigid (and that is granting a great deal),
it remains to be proved that a rigid trunk is more
resistant to storms than an elastic trunk.

GENERAL METHODS 139

If we have, then, a simple cavity for which
concrete is a suitable filling we know in advance
that it will be useless to try to make of the filling
a rigid mass. Our bracing has also been done
with that principle in mind. Knowing the plan
we are going to work on, we are ready to proceed
with the work of filling the tree. There are, as
has already been suggested, two ways of putting
concrete into a cavity — the dry method and the
wet method.

CONCRETE: DRY METHOD

The dry method is the commoner one. It looks
simple but it is not an easy job for a beginner to
set concrete up in an open cavity in such a way
that it will be well tamped and compacted, and yet
avoid " slumping " of the face of the filling. It
is well to begin with a job which slopes back a
little. It is not practicable, in this method, to
use a very large aggregate. Mix a mortar of
one part cement to four parts of natural gravel
which has passed through a half-inch screen, mak-
ing it so dry that a vertical wall can be cut in it
without slumping, and yet so wet that a handful
of it squeezed tightly will not fracture when the
hand is opened.

Set a pail of this mortar and a pail of wet
stones near the tree. After laying down a layer
of stones in the back of the cavity and out to

140 PRACTICAL TREE REPAIR

within four or five inches of its mouth, spread
over them a layer of mortar. The best trowel
for this purpose is a garden trowel to which has
been fixed a rather heavy handle about fifteen
inches long. Such a trowel scoops and carries
better and spreads as well as the flat, diamond-
shaped mason's trowel. The butt of the handle
is handy as a tamp. After thoroughly compacting

the cement about the
stones, bring up the level
of the front of the fill-
ing with mortar alone.
Lay each trowelful down
at right angles with the
mouth of the cavity.
Spread it back so as to
bond with the stones,
and pull it forward to
the face, pressing it
against a pointing trowel
held in the left hand.
Every layer must be
carefully tamped and
compacted by pounding
and pressing it from

Vertical section showing di-
vision of cement filling into
sections

above and pressing it in-
If the filling extends up
more than three feet above the surface of the soil
(or less in a small tree) divide the filling into

ward from in front.

GENERAL METHODS 141

horizontal sections. The interval between the
joints (or " disjoints," rather) depends upon
the amount of " give " in the trunk. Near the
base of a tree a foot and a half is sufficiently short.
Farther up, the sections should be smaller. One
sometimes sees complicated fillings which are di-
vided into sections of only four or five inches.
The necessity for such ample provision for cracks
usually indicates that the limitations of the use-
fulness of concrete have been exceeded. The di-
visions are produced by leveling off the top of the
concrete as the filling is being built up, and spread-
ing a sheet of paper over the level surface before
continuing the filling. Newspaper does very well
for this purpose, and has the advantage over
heavier kinds that it offers no resistance to the
trowel in cutting down
the face of the filling.
Thick tarred roofing
paper has its advocates,
however, their theory
being that it gives the
filling some elasticity un-

c\er rnmnrpQQinn The concr€te fillln£ must be

kept just below the cam-
After the filling is bium

completed, the next thing

to attend to is its outer surface and conformation.
At the edges the concrete should meet the wood
just below the line of the cambium. The distance

I42 PRACTICAL TREE REPAIR

back of the cambium depends on tbe thickness of
the dressing with which the surface of the concrete
is to be protected. There is a natural tendency
to rub the surface of the filling down smooth, but
the subsequent surface dressing sticks better to the
surface which results from cutting or paring down
the cement with a trowel. The conformation of
the filling should be graceful, following the curves
of the trunk, but no effort should be made to imi-
tate the bark or ridges of the natural tree. The
curve from one side of the cavity to the other
should not be full, but rather incline toward flat-
ness.

CONCRETE: WET METHOD

The method, which will now be described, of
filling cavities in trees with wet concrete mixture,
depends on the closing of the opening with a dam
of waterproof fabric (such as oil-cloth) held in
place by strips of canvas across the opening, the
dam being carried up the opening as fast as the
mixture is deposited. The work is performed in
the following way, a basal cavity of very moder-
ate difficulty being taken as an example. Having
completed the excavation and treated the interior,
fill the lower part, up at least to the surface of the
soil, with wet concrete. Then, if the tree is a
large one, tie two poles to the trunk, one each side
of the opening and six or eight inches from it.

GENERAL METHODS 143

They can be held in place at top and bottom by
ropes running completely around the tree, and at
intervals between by ropes around the back of the
tree. Separate the poles from the tree by a num-
ber of inch blocks. Have ready a piece of oil-
cloth or oiled canvas at least as wide as the widest
part of the opening and as long as it is; also a
large number of strips of canvas five or six inches
wide.

Brush the shiny surface of the oil-cloth with
light oil. Mix a batch of concrete, preferably
near the tree, making it so wet that a man stepping
on a pile of it will sink to his ankles. You are
now ready to continue filling up the cavity. First
hold the oil-cloth, shiny side in, against the open-
ing of the cavity, the top edge of it reaching a
few inches above the highest part of the opening
and tack it there with a couple of brads. Fit the
cloth, where it touches the ground, across the
opening and hold it in place with a few
shovelfuls of gravel. Tie a strip of canvas to
the bottom of one of the poles and carry it across
to the other pole in such a way as to hold the oil-
cloth in place. Carry the canvas back and forth
across the opening up to a point say eighteen
inches above the surface of the soil. Loosen the
oil-cloth from the brads holding it above, thus
exposing the opening of the cavity. The lower
part of the oil-cloth will of course be held against

i44 PRACTICAL TREE REPAIR

the opening by the canvas strips. Inspect the in-
side of the eighteen-inch wall or dam thus pro-
duced, making sure that it is firm and tight to the
edges of the opening. If it appears possible that
the mortar will escape along those edges, a rag or

Two stages in the process of filling a basal cavity with concrete
by the wet method

some waste or a bit of clay can be used to plug
up the loose places. Now shovel in the concrete,
spreading and tamping it at the same time. See
that it flows into every corner and that no part of
it escapes the tamp. When the concrete has
reached the top of the dam, give it a final tamp-
ing, level it off, and spread a sheet of newspaper

GENERAL METHODS 145

over it, in order to make a division, as described
earlier in the chapter. You are now ready to
start a new section. Raise the end of the oil-cloth,
tacking it up as before. Carry the strips of can-
vas back and forth across the opening until a
height of a foot or so is reached. Then drop
the oil-cloth, put in the concrete, and proceed as
before.

When the filling is completed it must be allowed
to stand for several hours, the exact time depend-
ing upon the weather, the richness and wetness of
the mixture, and the size of the filling. If possi-
ble, put in the filling in the morning and inspect it
occasionally during the afternoon. As soon as
it becomes resistant to the fingers and a little force
is required to cut into it with a trowel, take off
the canvas strips and the oil-cloth. Then chip
or scrape the filling off down to the proper level
and contour, starting with the spots which require
the most cutting away. If a pebble here and
there runs farther back into the concrete than it
is desired to cut, simply pull it out and leave a
hole there. If the surface resulting from this
process is not sufficiently smooth, dampen the sur-
face thoroughly and cover it with a thin stucco of
wet mortar made of one part cement and two
parts sand. The stucco should be as shallow as
possible; indeed, it is best simply to fill up the
deeper holes made by knocking out stones from

146 PRACTICAL TREE REPAIR

the filling. Shade the filling from the sun and
after it has become a little harder sprinkle it
with water occasionally to " cure " the surface.
Finally, treat the surface with a waterproof com-
pound or paint.

It is obvious that this method can be, indeed
must be, modified to meet special needs and special
conditions. If the filling is in a small tree the
poles at the sides can be dispensed with, and the
canvas strips can be run completely around the
tree. If canvas is not handy, rope can be used,
some slats and a piece of burlap, perhaps, or a
piece of old carpet, being laid against the oil-cloth
to stiffen it.

Some may think that a filling done in this way
will result in too flat a surface across the mouth
of the cavity. The writer considers a flattish
surface stronger, more favorable to the growth
of calluses, and better looking than a much rounded
surface, but if greater convexity is desired it
can easily be secured, either by leaving the canvas
strips loose, so as to let the oil-cloth bag out a
little, or by leaning a pole or two against the open-
ing inside the oil-cloth, to hold it back from the
opening. If the filling is so shallow that con-
vexity is necessary to give it strength, asphalt
ought to be used in place of concrete.

If for any reason it is desired to have the con-
crete harden very quickly, a ten per cent, solution

GENERAL METHODS 147

of calcium chloride can be used in place of pure
water. The mixture will harden three or four
times as fast as it otherwise would. This per-
centage represents about eight pounds of chloride
to ten gallons of water. The chloride costs about
twelve cents a pound in small quantities; much
less in larger ones.

Concrete fillings put in during frosty weather
must be protected several days with blankets or
straw. Some protection, also, is worth while
when fillings are put into street trees. Small boys
have a mania for scratching on fresh cement in-
scriptions which d6 not enhance its beauty.

SURFACE-DRESSING ON CONCRETE

Concrete absorbs water, especially when it is
only of moderate density, as concrete fillings are
likely to be. To head off this absorption and the
decay which usually follows it, every concrete
filling should receive a waterproof dressing over
its surface. For small fillings which are not much
exposed to the weather and dampness, a couple of
coats of tar will do very well, provided they are
applied after the concrete has dried out. In all
other cases it is best to give the concrete one or
more coats of some special concrete paint. The
writer uses Hoyt's cement paint, which has the
virtue of sticking to a slightly damp surface.
When the paint has dried a coat of tar can be put

I48 PRACTICAL TREE REPAIR

on as an additional protection and because black
is probably the best color for fillings. Many
workmen apply slaters' cement to the wood
just inside the mouth of the cavity, with the idea
of filling in advance the crack which always forms
between the concrete and the wood. I have not
found that method very successful, but I often ap-
ply the slaters' cement rather thickly to the region
of the crack after the filling has dried out.

FILLING WITH ASPHALT

There are many ways in which asphalt can be
used for filling trees. Invariably, however, it is
mixed with a cheaper material, being used as a
cement rather than as a homogeneous filling. The
materials thus cemented together may be sand,
sawdust, or excelsior.

Mixed with sand, as it is in paving, it cannot
readily be built up and sur-
faced, so that if sand is used
as an aggregate the cavity
must be given a front wall
of sheet metal to act as a
Section of cavity filled dam while the mixture is be-

alphalt "filling"' ing Put in and as a protection

to the surface after the job

is done. If this method is used a shallow ledge

must be cut along each side of the cavity, as for

ordinary tinning. A sheet of zinc is then cut to

GENERAL METHODS 149

fit from side to side of the cavity and is nailed to
the ledges. In the cavity, back of the zinc, is
now packed the hot sand-asphalt mixture. The
mixture is made by stirring about six parts of hot
sand (rather fine, and preferably of various sizes,
down to dust) into the melted asphalt. The mix-
ture resembles a heavy bran mash and can be
handled with a shovel or trowel. It must be
thoroughly tamped. When the filling has been
brought up to the level of the first length of zinc
another sheet is cut and nailed in place, overlap-
ping the first slightly, like shingles. Finally, the
metal is tapped over with a hammer to smooth it
out and is given a thorough waterproof dressing.
This method is of considerable value for filling
cavities whose sides are so shaped that the metal
can easily be fitted to the sides, and whose sides,
either naturally or as a result of bracing, are rigid,
the mouth of the cavity not opening and closing
slightly in storms, as it is so wont to do. If the
latter is the case the metal will be torn from the
nails which fix it to the wood. In many instances
the metal will be sufficient without the use of an
expensive backing of asphalt. In other cases a
cheaper backing will be found quite as satisfactory.
The value of the metal-front asphalt-sand filling
is therefore limited, because it cannot meet severe
demands and because moderate demands are as
well met by cheaper systems of cavity treatment.

150 PRACTICAL TREE REPAIR

Better fitted to do the things which concrete
has failed to do, and adapted to the treatment of
every sort of cavity, is the " asphalt briquette
system." l The central idea of the method is the
use of briquettes, of various sizes, made of excel-
sior, or excelsior and sawdust, bound together
with asphalt. A wall is built up, in the front part
of the cavity, of briquettes cemented together with
melted asphalt. To prevent the possibility of a
crack opening between the filling and the wood,
as invariably occurs with concrete, the briquettes
next to the wood are nailed to it. The wall of
briquettes is reinforced by braces from the back
of the cavity. The remainder of the cavity, back
of the front wall, is filled with any one of a num-
ber of materials, such as " asphalt staff " (ex-
celsior cemented together with asphalt), sawdust,
or cinders.

Besides the briquettes, there must be on hand
before work begins a supply of asphalt cement and
of fluxing oil, such as u Varnolene," a kettle in
which to melt the asphalt, another kettle, possibly
smaller, in which to mix asphalt and sawdust,
provisions for heating the kettles and for protect-
ing the grass while doing so, a supply of sawdust
and excelsior, some odds and ends of boards, ten-

1 An application has been filed for a patent covering this
method, and those who wish to use it should apply to Mr. C.
H. Hoyt, Citizens Building, Cleveland, who can also supply
the asphalt briquettes.

GENERAL METHODS 151

penny nails, some fairly heavy wire, and the
necessary tools, such as hammer, gouge, mallet,
and pliers.

The preparation of the cavity for an asphalt
briquette filling is not essentially unlike the prep-
aration for a filling of concrete. The decay must
all come out, of course, in either case.

For concrete the cavity must be wedge-shaped,
smaller in front than in back. For asphalt it is
desirable that the sides of the cavity be as near
perpendicular as possible to the face of the future
filling. There is no change in the rules as to the
handling of the cambium and the shaping of the
incision in order to facilitate the growth of the
callus over the filling.

The interior must receive a dressing just as for
concrete. A hot mixture of asphalt and a small
amount of fluxing oil is the best for the purpose,
because it stays sticky for some time.

Previous, however, to the application of this
dressing, such braces must be put in as are neces-
sary, and a method of reinforcing or bracing the
briquette wall must be decided on and provided
for. The different ways in which the wall can
be strengthened will be taken up later on.

If the cavity is a basal one and extends below
the ground, the lower part up to the surface of
the soil, or two or three inches above it, must be
filled with concrete, or partly with cinders or the

152 PRACTICAL TREE REPAIR

like. When the concrete is hard the work of
filling with asphalt begins.

Paint the upper surface of the concrete, which
has been leveled off, with asphalt. Have a kettle

Front view, vertical and
cross sections of a basal
cavity rilled by the asphalt
briquette system

of melted asphalt near the cavity. Drive a nail
nearly through one of the briquettes near its end.
Spear the briquette with an awl and dip it into the
hot asphalt. Lay it along side the wood with its
outer edge about a quarter of an inch back from
the cambium. Drive in the nail and pull out the
awl. If a wedge-shaped space remains between
the back part of the briquette and the wood, it had

GENERAL METHODS 153

better be filled up with a mixture of about equal
parts of asphalt and sawdust. Set a similar bri-
quette against the wood on the other side of the
cavity. Now you can fill in between the two bri-
quettes in place. Take a briquette on the awl, dip
it, and place it on its longer side on the concrete,
its front being flush with the first
briquette and with the edge of the W«|<J,
concrete. Lay another briquette
beside the first and continue the
course over to the other side of the
cavity. Lay on two more courses
in the same way. This will bring
the flat courses up to a level with
the top of the briquette nailed to
the wood at the sides of the cavity.
Start the next course by laying a briquette with its
narrow edge against the wood. Nail this bri-
quette to the wood and to the briquette below it.
Finish the course. Then, at each side, nail a bri-
quette flat against the wood. Build the wall up
between them, lay another course from wood to
wood, and so on.

This process is more complicated, naturally,
when the side of the cavity is slanting or curved.
The principal difference is that the soft asphalt-
sawdust mixture is more often called on to fill
crevices and corners. The necessary care re-
quired for fixing the briquettes at the edges of the

154

PRACTICAL TREE REPAIR

wall to the wood depends upon the degree of
probability there is that a crack will open up be-
tween the filling and the wood. If the briquettes
at the side are tightly nailed to the wood, when
the tree sways the enlargement of the mouth of

Arrangement of briquettes in an oval
cavity

the cavity will be taken up by the elasticity of the
briquette wall. If none of the briquettes is nailed
to the wood, a crack may appear, under certain
circumstances, along the edge of the filling.

In carrying up the wall it is well to keep its face
as smooth as possible, particularly at the sides, but
it is not difficult to smooth the surface with a ham-

GENERAL METHODS 155

mer, or to cut off projections with a chisel, after
the wall is finished.

At intervals, as it is built up, the wall will
need bracing. The amount of bracing required
depends principally upon the width of the wall.
If it is not more than a foot wide, no bracing will
ordinarily be needed. There are two types of
braces, those which prevent the wall from bulg-
ing out and those which prevent it from caving in.
The first function is best performed by wire, the
second by pieces of wood.

There are two good ways of handling the wire.
The most obvious plan is to drive some staples
into the back of the cavity and run short lengths
of wire from them to the wall. The easiest way
is to employ V's of wire having the ends bent down
at right angles. One limb of the V-shaped wire
is threaded through the staple and the bent ends
are driven into the briquettes. One of these V's is
put into every second or third course. Another
way is to use the same kind of V's, but to anchor
them, not to staples, but to a strong wire run from
one end of the cavity to the other from bolts or
pieces of wood across its top and bottom. The
advantage of this last plan is that greater elasticity
is permitted to the wall without loss of strength.

The wooden braces also take several forms.
For example a board can be laid on the surface
of the back filling^ fitting in snugly between the

Wooden brace for asphalt-
briquette wall

156 PRACTICAL TREE REPAIR

briquette wall and the rear wall of the cavity.
Or a little longer board can be built right into
the briquette wall, being nailed to the briquettes
and extending back far enough to touch the back
of the cavity. Such a brace can be made to resist

a pulling as well as a
pushing force by nailing
to it a cross-piece fitted
into a part of the cavity
which is wider than the
mouth.

It must not be sup-
posed, however, that
the asphalt wall is of
itself weak. On the contrary, it is very strong,
but the conditions surrounding work in trees are
so extremely trying that braces which may never
be called on to undergo an ounce of strain ought
to be put in, if only by way of insurance.

The filling in the space back of the wall forms
a backing for the wall, helping to hold it in place.
The filling also helps in putting in some types of
braces and it holds them in place. On the whole,
I am inclined to consider coal ashes or fine cinders
the best material for filling the space back of the
briquette wall, on account of their packing qual-
ities, their cheapness, and the fact that they need
no treatment to make them proof against insects
and decay.

Cavity in large red maple. The lower part was filled
with concrete and the upper part was tinned

GENERAL METHODS 157

This back-filling should be carried up along
with the briquette wall, and it should be thoroughly
pressed or tamped into place in order to prevent
subsequent settling. If it is felt that these ma-
terials would not give a sufficiently staple backing
for the wall, the entire filling can be made of bri-
quettes, of hot asphalt-sawdust mixture, of " as-
phalt-staff," or of ordinary staff made of excelsior
and plaster of Paris.

In large cavities it is well to provide for the
ventilation of the filling. The best way to do
this is to leave out a briquette near the bottom of
the wall and another near the top. The holes
thus formed must be provided with a netting to
keep the filling in and insects out. The face of
the wall for an inch or two around the opening
can be painted With hot asphalt and a piece of
copper or brass netting can be pressed against the
opening and held there until the hardening asphalt
cements it in place.

The surface of a filling made in accordance
with these specifications for the asphalt-wood
briquette system is likely to be rather irregular,
but it is not likely to be irregular enough to inter-
fere with the growth of the calluses ; yet it may be
desirable, from the esthetic standpoint, to make
it smoother. It is not difficult, with a broad,
sharp chisel or gouge, frequently dipped in oil,
to cut away the corners of projecting briquettes.

1 58 PRACTICAL TREE REPAIR

Then the surface can be warmed with a gasoline
torch, not held too near, and irregular places can
be pounded down with a mallet. Finally, the
entire surface must be given a heavy coat of hot
asphalt to which about one fifth of its bulk of
" Varnolene " oil has been added. In some
cases it may be worth while to reinforce this
dressing with cotton padding in the way that has
been described in discussing the treatment of
wounds.

Besides being used in the form of briquettes, a
mixture of asphalt with excelsior or with sawdust,
at the rate of about a pound of sawdust to three
pounds of asphalt, has great value applied directly
to the cavity, especially for filling small holes.
All that is necessary is to melt the asphalt, mix
in the excelsior or sawdust and press the mixture
into the cavity. A little practical experience will
teach any one the points which must be observed
in handling these materials. The " asphalt staff,"
for instance, must be held in place a few minutes
until it hardens. After a filling of staff has
hardened it can be trimmed to shape, and can be
nailed to the wood by nails driven slantwise
through its edges. Finally, it must receive a
thorough dressing of metal or fluxed asphalt.
Many combinations of briquettes with staff or
asphalt-sawdust mixture will at once suggest them-
selves.

CHAPTER IX
THE VARIOUS TYPES OF CAVITIES

THIS general description of the procedure to
be followed in the filling of cavities with the
various materials employed for that purpose must
in practice constantly be modified to suit special
conditions. In the following pages the com-
moner types of cavities
will be taken up and the
principal measures and
materials best suited to
the handling of each
will be described.

Rotten knot-holes
and decayed stubs con-
stitute the common-
est type of cavity.
Many large and serious
cavities have their
origin in the stubs re-
sulting from the death
of limbs or the incor-
rect removal or treatment of limbs by pruners.
Holes of this kind are extremely common, and it

159

Section of rotten stub, with
dotted line indicating cor-
rect excavation

160 PRACTICAL TREE REPAIR

is often necessary that the treatment given them
be rapid and economical. If such a cavity is
shallow the best way to handle it is to employ the
open system, to be described in the next chapter,
in which no filling is used.

Deeper holes, in which the open treatment
would involve too large an incision and the cutting
away of too much bark, must be filled. Although
in some cases complete removal of the decayed
wood is neither possible nor desirable (and of
those cases we shall have more to say in a later
chapter) , for the most part the general principles
of cavity work apply as well to small holes as to
large ones.

The first step, then, is the removal of the de-
cayed wood. To do this thoroughly often in-
volves considerable difficulty. The mouth of the
hole must usually be enlarged, especially down-
ward, and it may be necessary, if the decay runs
far down the trunk, to cut in from below to get
at it. More than one such opening may be re-
quired. In that case, a considerable distance
should be left between the openings, for other-
wise the intervening patch of bark will die.
These holes must be cut only when it is absolutely
necessary, for every such opening increases the
risk of the entrance of water and of other troubles
with the filling. The excavation finished, the

VARIOUS TYPES OF CAVITIES 161

mouth of the hole should be trimmed up and
cleared of ingrowing callus.

The filling material to use in such a cavity de-
pends upon its shape and upon its position in the

Deeply decayed knot-hole and the same excavated and filled with
asphalt

tree. If it is in a large trunk where there is likely
to be but little strain on the filling, cement will do
very well, after, of course, a thorough dressing
with some form of asphaltum. If, however, the
hole is in a limb, and at a point where there is con-
siderable twist and bend, cement will not do, for
it will break up and perhaps be forced out of

1 62 PRACTICAL TREE REPAIR

place. In that case the filling must be elastic.
Use asphalt briquettes and a mixture of hot as-
phalt and sawdust, or the mixture alone. In
every case a dressing of asphalt must complete the
filling.

For the odds and ends of small holes, in so far
as they need filling, a mixture of asphalt and saw-

.Sawdust

Shallow cavity under a callus filled with asphalt-
sawdust mixture

dust, or excelsior, or both, is the safest material
to use. For instance : It is often found that the
surface of a large old bark wound is decayed three
or four inches deep. In cleaning away the decay
the healthy calluses at the sides of the wound
may be undermined several inches. The asphalt-
sawdust mixture is just the thing with which to
fill in under the overhanging callus. A few nails
can be driven through it as it is cooling.

The commonest and simplest form of large

VARIOUS TYPES OF CAVITIES 163

cavity is the basal cavity. Basal cavities are
caused by decay which enters the trunk at or near
the ground, through a wound in the bark, or
through a dead root. The only difficulties likely
to be met with in handling such a cavity are the
thorough excavation of the decay in the roots,
if it has worked deeply into them, and the correct
handling of the filling in relation to the lower
parts of the incision, where complications may be
produced by the growth or death of roots. As
regards the excavation, every effort must be made
to make it complete. If necessary, the opening
of the cavity can be enlarged and carried up the
trunk, or a new opening can be made, preferably
in one of the depressions between the main roots.
If the fungus causing the decay is one which de-
stroys the heartwood only, it will not be necessary,
in case it has worked down into the large roots,
to follow it far. The decay is likely to cause
less damage in the root than would an incision
large enough to make possible its complete re-
moval. But as far as the excavation is carried
it must be thorough, so that there may be no
connection between the remaining decay and the
heartwood of the trunk. In making incisions in
and about the roots, care must be taken that the
free flow of sap is not sacrificed to neatness of
outline and ease of filling. In order to " ground "
the filling correctly it is usually necessary to dig

1 64 PRACTICAL TREE REPAIR

down a foot or so just in front of the opening
of the cavity. The soil should be dug away from
the roots wherever there is any decay or possibil-

Views and sections illustrating the excavation and filling of a
simple basal cavity

ity of decay, and the grounding and drainage of
the filling should be carefully provided for. If
the decay has worked down to the ground under
the trunk, as it often does in trees which have not
large tap-roots, the humus and soil must be dug

VARIOUS TYPES OF CAVITIES 165

away several inches so as to give a chance to in-
spect and treat the remaining roots.

All decay having been removed, but little more
cutting is usually required. No great effort should
be made below the surface of the soil, as is often
necessary in handling openings in the upper trunk
to arrange the edges of the cavity in such a way
that the calluses will heal over the filling. It is
possible to do much in that way only at the foot
of the filling, in connecting up the filling with the
large roots usually found on each side of a basal
cavity. The patches of bark which have to be
removed from the roots in this operation are of
slight consequence, on account of the fact that
they are aside from the main flow of sap.

Basal cavities of the type we have been dis-
cussing do not often need any bracing. The cen-
ter is so much larger than the mouth that bracing
is not frequently required to retain the filling in
place, and it is not possible to add much strength
to a tree by putting in braces so low down in the
trunk.

As a dressing for the inside of the cavity, tar
will do very well, for the good drainage removes
the principal reason for a heavier covering of the
wood.

The work of filling the excavation is fairly sim-
ple. If there are any pockets, such as might be
caused by removing the decay from a root, they

1 66 PRACTICAL TREE REPAIR

must be filled up with asphalt or a heavy mixture
of ashes and tar. The next step depends upon
the nature of the bottom of the excavation, espe-
cially as regards the number of exposed roots.
If the soil has been dug out from beneath the
crown of the roots, it is usually better to replace
it with packed ashes or gravel before beginning
the concrete filling. The reason for this is that
these materials do not pinch growing roots, as
concrete does, and yet they are effective guards
against insects. In front, however, the concrete
ought to be carried fairly deep into the ground,
especially if there is any idea that the filling will
serve as a strengthening buttress to the tree.

The concrete filling should next be put in.
Though it may seem that the tree can sway but
little so near the ground, it is usually advisable
to divide even a low basal filling into sections, in
order to anticipate and control the formation of
cracks. The first division may be two feet, more
or less, from the ground, according as the tree is
large or small.

Concrete fillings of basal cavities can often be
left without any surface dressing. As a rule,
however, it is safer to paint them, after they have
hardened, with tar or asphalt, giving particular
attention to the edges.

In cases where the decay, starting at the base
of a tree, has worked upward in the trunk, the

VARIOUS TYPES OF CAVITIES 167

proper treatment is identical with that just de-
scribed for simple basal cavities, with the exception
that braces may be required in order to prevent
the opening of cracks at the sides of the filling.

Much more difficult to handle than basal cavi-
ties are those in the upper part of the trunk,
caused, for the most part, by the wrenching out
of a large limb or by some severe injury to the
bark. The difficulty of the excavation depends
upon the age of the injury. If the decay has
worked far up or down the trunk it may be neces-
sary greatly to enlarge the original opening.
The direction and size of the enlargement should
be investigated in advance by sounding the tree,
if necessary, with a half-inch bit. Once the exact
extent of the decay is known, it is easy to deter-
mine the size of the opening necessary for the
complete removal of the decay. If the shell of
the tree is thin it is best simply to enlarge the ex-
isting opening, but if a considerable thickness of
sound wood remains, it is well to try to get at the
decay from separate openings, above or below the
original one, but not less than a foot from it. Or
the new opening may be made on another side of
the tree if a good opportunity presents itself — a
bark wound, for instance, a rotten stub, or a very
slow-going area — to make an incision without
doing much damage to the tree. The reason for
the difference is that the wood between the main

1 68 PRACTICAL TREE REPAIR

opening and the auxiliary ones is left for its
strengthening value, and if the shell is thin no
such value is present. Then, too, a thin patch of
wood between two holes, one of which is above
the other, is likely to die, dry out, check, and ad-
mit new decay. Once the size and place of the
openings are decided on, they should be made,
for to delay each inch of enlargement of a cavity
until it becomes absolutely necessary to make pos-
sible the use of the gouge, means that the work
is constantly being done at a disadvantage. It
is all hard where part of it might be easy.

The great point about handling the excavation
of this type of cavity is to make sure, if concrete
is used as a filling material, that good drainage
is provided. This means that there must be a
downward slope from the lowest part of the cav-
ity, inside, to the lowest part of the opening. If
such is the case, any water which may enter the
cavity before the crack between the concrete and
the wood is covered by the growth of callus,
will be drained out at the bottom. To be sure,
it is not very reassuring to have to provide for
such a possibility, but experience has shown that
it is wise to provide for the disposal of water in
cavities, when filled with concrete, even though
the correct dressing or the cavity and of the outer
surface of the filling may reduce the possibility
of the entrance of water or of damage resulting

VARIOUS TYPES OF CAVITIES 169

from it if it should enter, to a minimum. When
too great an excision of sound wood is required to
secure drainage, the lower part of the cavity, up
to the level of the opening, can be filled with
asphalt, the balance of the cavity being concreted.

Careful bracing is ordinarily very essential to
the successful treatment of a large trunk cavity.
The amount of iron to be used, and its distribu-
tion, of course depend upon the strength of the
remaining sound wood and upon the strain it is
subjected to. Cavities having an opening of any
considerable vertical dimension generally need
horizontal braces. If the excavation has left the
trunk very weak the tree as a whole should be
braced to a stake or to a neighboring tree, as will
be described in the chapter on bracing. The pos-
sibility of reducing the strain on the trunk by
pruning in some of the branches should also be
considered

The dressing of the interior of a trunk cavity
should be as thoroughly done as it possibly can be,
and the most effective materials should be used.
If the inner surface is easy to get at, melted as-
phalt is the ideal dressing; if difficult, a dissolved
asphalt is likely to be more satisfactory. The
braces must be coated, of course, along with the
wood.

With the choice of a material for filling, we
come to the most serious problem presented by

170 PRACTICAL TREE REPAIR

this type of cavity. General rules for the choice
of filling materials have already been laid down,
and there is little that need here be added to them.
Asphalt is distinctly the best material, but if the

opening is reasonably
small, the cavity well
drained, and the prob-
able strain on the filling
not great, a concrete
filling, well put in, may
be fairly satisfactory.
The surface of the
concrete, if used, must
be given a waterproof
application, after it has
thoroughly hardened.

When injuries to the
trunk occur near crot-
ches, very bad cavities
often develop. They
are due, usually, to the
death of a large limb or the death or breaking off
of the upper part of the trunk. The resultant
cavity is called a " saddle." It is hard to make
a good job out of a saddle filling, for the reason
that parts of the filling are likely to be horizontal
or nearly so, making waterproofing difficult, while
the large amount of sway and movement in the
branches up which the saddle extends makes it

Typical saddle-cavity show-
ing distribution of braces

VARIOUS TYPES OF CAVITIES 171

doubly difficult to keep the filling water-tight.
The wood on the upper side of limbs, also, grows
much more slowly than that on the under side,
and calluses are formed with equal slowness. Sad-
dles, therefore, are likely to be healed over very
slowly, so that though good work is especially
difficult, it is also especially necessary.

The solution lies in correct bracing, correct fill-
ing, and correct dressing of the surface of the
filling.

In bracing the first thing to be done is to put
in a brace up above from one limb to another or
from the trunk to the weak
limb, in such a way as to
take most of the strain off
the base of the limb. Then
bolts must be run through
the saddle or just below it,
in order to minimize the
amount the mouth of the
cavity will open and shut intr^ollow splil

during a high wind. It

may be that some short pieces of gas-pipe or of
hard wood can be fixed in the cavity, pried in in
such a way as to make the walls as nearly rigid
as possible.

Cement should never be used in filling a saddle
cavity. If the tree is not worth a filling of asphalt
the cavity should be left unfilled.

172 PRACTICAL TREE REPAIR

A split crotch is another hard proposition. If
decay has entered it may be necessary to enlarge
the crack between the limbs or to make other in-

Crotch cavity braced, ready Bracing of a split
for filling crotch

cisions in order to get at the rotten wood. In
such a case the treatment should be guided by
what has been said about saddle cavities. If,
however, decay has not entered, the crotch should
be cleaned, as far as it easily can be, of loose bark
and other debris. If damp it should he left a

VARIOUS TYPES OF CAVITIES 173

while to dry. Spray it with creosote, then build
up a dam of moist clay, covering the crack nearly
to the top. The clay can be held in place by
boards, which are themselves held by ropes around
the tree. Fill the split by pouring in hot asphalt
through the opening at the top. An asphalt of a
rather low melting point, or one slightly fluxed
with oil, is preferable to a very hard one. The
asphalt must ordinarily be used clear, but if the
crack is a large one it may do to mix some saw-
dust with it.

The braces through the split limbs and also,
preferably, up above, must be set in place before
the asphalt is poured, and then
tightened up after it has hard-
ened. It is in many cases well
to put in a pair of bolts through
the trunk at an angle with the
plane of fracture.

The last form of cavity we
shall consider is the " chimney Split trgeethbe°rlted to~
cavity," which results from the
complete decay of the heartwood of a tree. It is
almost invariably marked by a basal opening at
the ground and another large opening at the top,
where a large limb or the top of the main trunk
itself, has been broken off. The hard proposition
connected with this type of cavity is the excava-
tion of the decayed wood. If the decay is diffi-

i74 PRACTICAL TREE REPAIR

cult to get out and the line of separation between
the sound wood and the decayed wood is not well

marked, and especially
if the decay has worked
up into a number of
branches, it is usually
not worth while to try
to excavate and fill the
tree. It is better by
far to brace the tree, if
it needs it, fumigate
the cavity, spray it per-
haps with carbolineum,
make all openings in
the tree water-tight, and
use the money saved by
not filling it in better-
ing the soil or planting
a new tree. In other
cases, especially when

Vertical section of a hollow '

tree, showing the basal open- the decay has proceeded

^rther, it may be com-

asphalt briquettes. The in- paratively easy to get
tervening space is rilled with - . -

cinders most of the rotten wood

with the help of a hoe

and long-handled gouges. Sometimes the de-
cayed punk can be expeditiously got rid of by sat-
urating a part of it at a time with coal oil and burn-
ing it out, care being taken to control the draft.

VARIOUS TYPES OF CAVITIES 175

The decay substantially cleared away, the cav-
ity should be dried by leaving it a few days or
by building a fire at the bottom of it. Then the
inner walls must be sprayed thoroughly with car-
bolineum, a little loose soil being thrown into the
bottom of the cavity to catch the drip, which might
injure the roots. If the cavity walls are fairly
smooth and easily accessible they may now be
painted with asphalt in some form.

The filling should be adapted to circumstances.
If there is an opening at the base, the lower part
of the chimney can be treated like an ordinary
basal cavity, being filled with concrete. Above
this point, if there is a fairly large stretch of trunk
without openings, it can be filled with packed
cinders or gravel, and then a filling of asphalt can
be set in at the top of the cavity. To fill the
entire trunk of a hollow tree with concrete, to
try to " put in a new back-bone," as one firm of
tree surgeons has claimed it could, is at once waste-
ful and futile.

In case, for any reason, it is not desirable or
feasible to fill the upper part of the chimney with
cinders, it can be left open, and the filling of the
top opening can be supported on a platform built
just below it. Such a platform can be made of
boards on bolts run through the trunk, or the plat-
form can be made of wires woven back and forth
between a dozen nails or staples driven into the

176 PRACTICAL TREE REPAIR

inner wall of the cavity. Over the boards or
wires any material or combination of materials
(such as boards, straw, heavy paper, or burlap)
can be used as a support for the filling of concrete
or asphalt. But tinning is usually the best way
to handle the top of a chimney cavity.

CHAPTER X

THE TREATMENT OF CAVITIES
WITHOUT FILLING

THE tree surgeons have one almost universal
characteristic. They all decline the half
loaf. If they cannot have the whole loaf, they
will have none. If they cannot do a perfect job,
get all the decay out of the tree and replace the
destroyed wood with a neat filling, they will not
touch it. At least, so they say. If there are
ever published the " Confessions of a Tree Sur-
geon's Foreman," perhaps we shall discover that,
more often than we have ever guessed, they have
been content to receive several good slices less
than the whole loaf. A coating of tar and a fill-
ing of cement can cover a multitude of sins. Be
that as it may, the writer believes that, though
in many cases decay cannot be completely re-
moved, there are few cases in which the progress
of decay cannot be retarded, or at least in which
the final result of the decay, the destruction of the
tree, cannot be materially postponed. The ways
and means of accomplishing these ends constitute
the subject-matter of this chapter. There are

177

178 PRACTICAL TREE REPAIR

also included in it discussions of various methods
of treating cavities which premise a complete ex-
cision of the decayed wood, but which do not call
for the filling of the cavity.

The most important way in which the life of a
tree in an advanced stage of decay can be pro-
longed is by severe pruning and liberal manuring.
The pruning takes off much of the strain on the
tree and invigorates the remaining parts. Al-
though this treatment does not, strictly, fall within
the legitimate field of this book, on account of the
vital interest of the subject to almost every per-
son who is likely to look into a book of this kind,
I shall venture to quote here a few lines from two
editorials, written by the editor, Prof. Sargent,
which appeared in the old " Garden and Forest."

" The vigor of a tree depends upon the power
of its leaves to elaborate plant food. The larger
the leaf surface exposed to the light, the greater
will be the vigor of the tree. The object of prun-
ing, therefore, is to increase leaf surface. If
half a branch of a decrepit tree, bearing small and
scattered leaves, is cut away, the leaves which
will grow upon the half which is left will be so
large that their total area will often be more than
double the total area of the leaves upon the whole
branch before it was cut. ... A tree on the de-
cline should have its main branches all shortened
in from one-third to one-half their length. . . .

TREATMENT WITHOUT FILLING 179

Nearly all our forest trees bear severe pruning
of this sort, and improve under it." Prof. Sar-
gent also insists on the importance of fertilization.

It need hardly be said that these extracts do
not constitute complete advice as to when severe
pruning ought to be employed, nor full directions
for carrying out the work.

This is one way in which the arboriculturist,
recognizing the impossibility or the prohibitive
expense of eradicating completely the decay in a
veteran tree, can defer the time of its dissolution
by a much less expensive, and yet perhaps no less
effective, treatment. Yet it would not do to
create the impression that severe pruning and
filling are alternative processes. If it is thought
that the tree will respond to the pruning treatment
it should be pruned. If, in addition, filling the
cavities promises to be successful and not too ex-
pensive, the tree should be filled.

There are treatments, however, which are al-
ternatives to filling and which fall within the
realm of tree repair. Their purpose, for the
most part, is to secure those benefits of cavity fill-
ing which are most cheaply attained, while sacri-
ficing those less easily secured. Some are baldly
practical, seeking only to stop decay and giving
no thought to the appearance of the tree when the
work is done. Some of them, though not includ-
ing fillings, have been brought forward with the

180 PRACTICAL TREE REPAIR

•

claim that they perform all of the functions as-
cribed to fillings, and perform some of them better
than fillings do. Where the complete eradication
of the decay is obviously impossible, or where,
on account of the secondary value of the tree, or
any other of the reasons enumerated in the sixth
chapter, a large expenditure is not deemed wise,
the weakening of the tree can be retarded by
treatments which, makeshift though they be, often
return larger percentages of benefit than do the
far more expensive fillings.

There is at present a strong movement among
practical arboriculturists, the men connected with
experiment stations and with large city parks, in
favor of the omission of the filling in the treat-
ment of cavities. " Clean out every particle of
decay, brace the trunk if it needs it," they say,
" paint the interior of the cavity with a heavy
dressing, and let it go at that." The arguments
in favor of that method are four. First, it saves
the cost of the filling. Second, there is less dam-
age to the tree, because no sound wood need be
cut away in preparation for the filling. Third, it
does not suffer from the disadvantage of a cement
filling that it " draws " water and increases the
probability of a reinfection of the wound.
Fourth, it does not suffer from the disadvantage
of all fillings, that it is impossible to inspect the
work after the filling is in place to determine

TREATMENT WITHOUT FILLING 181

whether further excavation is necessary and, if so,
to continue it. This is easy when the filling is
omitted. The cavity is inspected annually, and if
there is any decay it can be removed.

On the other hand it is claimed that several
advantages attained by the filling are lost by omit-
ting it. First, no provision is made for the sup-
port of the callus, which, without support, cannot
bridge the wound. Second, the provisions against
the entrance of insects and fungi are inadequate.
Third, the strengthening effect of the filling is lost.
Fourth, if the excavation is a large one it will in-
variably ruin the beauty of the trunk of the tree.

In answer to these claims the " ultra-modern-
ists," to borrow a phrase from a rather remote
field, assert, as to the first of them, that in the
case of large wounds in old trees callus growth is
so slow as to be negligible, and that when calluses
do grow, they help the tree quite as much physi-
ologically and almost as much physically when they
roll into the cavity as when they bridge over it.
Of the second claim they say that a heavy dress-
ing, periodically renewed, is as good as a filling,
and of the third, that the strengthening effect of
the filling is highly problematical and cannot be
great in any case. As regards the esthetic argu-
ment, they frankly admit that they are not work-
ing for looks but for effectiveness.

As to the technique of the " open system,'* but

1 82 PRACTICAL TREE REPAIR

little need be said. The excavation is made in
substantially the same way that an excavation
for a filling is made, though with the important
differences that no wood has to be taken out of

Four sections of the same cavity, showing it before excavation,
filled with concrete, covered with zinc and treated by the open
system

it so as to shape the excavation in such a way that
it will retain a filling, and that no provision has
to be made for a " cambium edge line " from
which the callus can grow out over a filling. In-
growing calluses need not be removed. If in-
cisions through the healthy bark have to be made
they should conform in shape and location to the

TREATMENT WITHOUT FILLING 183

rules for making incisions formulated in a previ-
ous chapter. No tongues or patches of bark can
be left, which are cut off from the main flow of
sap, for they will die, decay, and expose the wood.
Drainage must be looked out for. If a " pot "
is left at the bottom of the cavity it must be filled.
The best way is to pack in some largish stones

Two ways of handling a " pot " at the bottom of a cavity treated
by the open system

and submerge them with hot asphalt. Though,
theoretically, if the pot is correctly painted it will
be water-tight, so that water standing in it would
do no harm, it might do some damage with the
help of Jack Frost, and would be sure to become
a breeding place for mosquitoes.

The dressing of the interior of the cavity must
be done with the greatest care. After a coat of
hot carbolineum, put on one or two coats of coal
tar or of one of the asphalt preparations, seeing

1 84 PRACTICAL TREE REPAIR

that not a speck of the wood is left exposed. In-
spect the dressing yearly.

The open system is especially suited to the
treatment of small cavities in healthy trees. Such
a one is illustrated in the accompanying drawings.

One of the first methods of dealing with wounds
and cavities was to cover them with sheet metal.

Shallow decayed spot gouged out
and tarred, without filling

The idea was not only to keep out the elements
and insects and fungi, but also to provide a sup-
port for the calluses growing from the sides of
the mouth of the cavity. It was at one time gen-
erally thought that tinning would prove the best
treatment for almost every type of cavity, but it
is now realized that its value is rather strictly
limited. These limitations follow directly from
the nature of the material and the way in which
it is applied, and a discussion of them will be de-
ferred until those points have been taken up.

TREATMENT WITHOUT FILLING 185

The kind of excavation required in order to
prepare a cavity for tinning is in some ways like
an open system excavation, and in other ways like
excavation for an asphalt or concrete filling.
No provision need be made, of course, for the re-
tention of a filling. But fitting a cavity for tin-
ning is unlike treating it by the open system in that
a line all around the opening of the cavity must

The correct way to cut an old callus in preparation for tinning
and manner in which the new callus will spread over the tin

be laid out, up to which the tin shall come, and
all living bark and cambium inside of this line
must be removed. This line must keep as close
to the cavity as possible, so that the area to be
callused over may be minimized. The opposite
sides of the line must be as nearly as possible in
the same plane, so that the tin can be put on with-
out wrinkling it. And the line must be so located
that there shall be just inside of it a strip at
least three-quarters of an inch wide, of fairly
level, strong wood, upon which to nail the edges
of the metal.

1 86 PRACTICAL TREE REPAIR

It is absolutely essential that no growing bark
be permitted to remain inside of the cavity, for
it would be almost certain, ultimately, to press
against the lower surface of the tin and displace
it. And it is especially important that the edges
of the metal be laid and nailed in such a way that
no growth can get under them, and in such a way
that a callus will grow over them and the nail
heads as soon as possible. The way to make
sure that no living bark is left is either to chip off
the bark and wood just under it, or else, as in
the case of old inrolling calluses, to peel off the
bark and to scrape away all of the exposed cam-
bium. It is desirable, at the line at which the tin
meets the bark, that a little of the sapwood be
cut away, so that the tin may be a trifle below
the starting callus.

As an interior dressing, a thorough coat of car-
bolineum will be enough. No heavier dressing is
required, for there is no weathering to be guarded
against and no bond to be produced between filling
and wood.

Several different forms of sheet metal are used
in tinning trees, tin itself, odd as it may sound,
being the least valuable. But the word " tin "
is so very handy, both as a ,noun and as a verb,
that it is the natural one to use in speaking in a
general way of sheet metal.

Sheet zinc comes in several degrees of hardness,

Linden on Boston Common, treated by the "open"
system. The tree was so badly damaged by the
leopard moth that it was not considered worth rilling

TREATMENT WITHOUT FILLING 187

a rather soft grade being best suited to tree work.
The most useful thickness is No. 9 zinc gauge,
which comes in sheets and rolls of various lengths
and costs not far from seventy-five cents a square
yard, retail. Heavier and lighter, as well as
harder, zincs have their uses.

Galvanized iron is of course zinc-plated sheet
iron. It is heavier and stronger than sheet zinc
and is valuable for large flat work. No. 22, sheet
iron gauge, is a good weight. It comes in sheets
two feet by seven, which cost about two dollars.

Soft sheet copper is a pleasant material to
handle and is a good material for covering wounds
where much bending and fitting is required. It
is the most permanent sheet metal, but is of course
not strong. It cannot often be substituted for
zinc on account of its high cost, the thickness
weighing ten ounces a square foot costing about a
dollar and a half a square yard.

Tin-plated sheet iron (roofing tin) does fairly
well for small jobs where there is not much strain
and where it can be kept painted. The weight
stamped 1C is the one oftenest used.

Ordinary sheet iron, such as is used for making
stove-pipes, is the cheapest sheet metal, but it
requires extraordinary precautions to prevent rust-
ing, and one is never quite sure of it. The nails
used are zincked shingle or basket nails, with
fairly large heads.

1 88 PRACTICAL TREE REPAIR

The way in which the metal is applied to the
opening of the cavity is governed by the nature
of the strains .on the metal, after it is in place.
Those strains have two origins. The pressure
of the ingrowing callus upon the tin produces one
kind of strain, a strain which falls first on the

Before-and-after views of a typical job of metal work

nails and then on the metal itself. This strain
is not often the source of trouble, for as soon as
the callus grows over the nails they are so
anchored that they cannot give way. The other
strain is far more serious. It results from the
tearing and shearing forces produced by the bend-
ing and twisting of the tree. If the opening is a
large one, in a storm its sides will shorten and

TREATMENT WITHOUT FILLING 189

lengthen, spread apart and come together. If
this strain is too great it rules out the use of metal.
A moderate amount, however, can be accommo-
dated in various ways.

The first thing that can be done is to reduce
the amount of strain on the metal by bracing the
sides of the cavity together, exactly as is done in
preparing a cavity for a concrete filling. If

Cross section showing how zinc can be bowed in to allow for
spreading of the sides of a cavity

there is a good, strong nailing edge at each side,
a few narrow strips of sheetiron can be nailed
across the opening to help keep it rigid. The
strain can also be met by dividing the metal up
into sections of greater or less size, according to
the amount of sway. When that is done the work
must begin at the bottom, each successive section
being lapped over the one below it an inch or two.
Under certain conditions the tendency of the
nails to tear through the metal under stress can
be lessened by bowing the metal in a little so that

190 PRACTICAL TREE REPAIR

the spreading of the sides of the cavity is accom-
modated by the surplus metal.

When the incision is completed and everything
is ready for the tin, proceed as follows: Make
a paper pattern of the whole opening, if it is
small, or of the lowest section if it is large, mak-
ing sure that the paper is not stretched or folded
in a way the metal itself is not capable of. Lay
the pattern on the metal, scratch with a nail the
line of its edge, and cut out the shape. Fit the
metal over the opening, trimming off the edge
here and there if necessary to make a perfect fit.
Paint the back of the tin with tar or paint. Paint
the edges of the opening, the strip of wood, that
is, to which the tin will be nailed, with heavy liquid
asphalt. Now fit the tin into place and tack it
there with nails four or five inches apart. If the
metal is heavy it is a good idea to punch holes
around its outer edge with a small punch or a
sharpened spike. The nails must be very near
together — an inch or even as little as half an
inch apart. Where circumstances permit it, stag-
ger the nails, putting some farther from the edge
of the tin than others. After nailing it is a
good idea to go over the edge of the metal with
some such tool as a dull cold-chisel, pounding the
edge into the wood a little so that the growing
callus cannot by any chance get under it.

It is hardly necessary to say that this work is

TREATMENT WITHOUT FILLING 191

not so easy as the simplicity of the above direc-
tions would indicate. A great deal of ingenuity
is required to fit the metal neatly and closely.
For instance, in order to make it conform to a
" valley " it must sometimes be slit in from the
edges and overlapped.

The treatment of the outer surface of the metal
is the last but by no means the least important
process in tinning cavities. A, very heavy dress-
ing should be put on, especially around the edges.
Not only is this last necessary as a precaution
against the entrance of water, but also against
rust, especially of the nails. A heavy dressing
also tends to prevent the starting of the nails in
zero weather.

Tin work requires a certain amount of after
care, like every other sort of work in trees. The
surface dressing may need renewal after a few
years. There is one objection to tinning which
may have to be remedied if it develops. That is
the tendency of the tin, or such other metal as
may be used, when there is a high breeze, to
" snap," a noise which means that the tin is being
forcibly, though slightly, wrinkled. After a year
or two the tin gives way in one or two places and
the noise stops. As soon as a piece of tin begins
to snap one or more horizontal slits must be cut
in it with a can opener or a sharp cold-chisel, so as
to relieve the tendency to buckle. The slits must

1 92 PRACTICAL TREE REPAIR

be covered with cotton-batting soaked with an as-
phalt dressing. It is likely that a back filling of
cinders or sawdust would help to avoid the dis-
advantages of tin work, but the writer has never
tried that method.

The nature of the principal strain upon the
metal and the way in which it gives way to it, sug-
gest the correct limitations to be placed upon the
use of metal for covering cavities. It is not so
much size which causes the failure of a job of
tinning, but rather the amount of variation there
is, under stress of the wind, in the size and shape
of the opening. A large cavity in a firm trunk is
much easier to tin successfully than a smaller cav-
ity in a bending and twisting limb. An opening
in a trunk or branch which swings about much
ought not ordinarily to be tinned, as the work
is almost certain to be unsatisfactory. It is some-
times difficult for a beginner to determine whether
a given opening is likely to be variable in size or
not. In that case it is best to wait until a windy
day comes, when any variation in the size of the
opening can be observed.

Tinning is very well suited to the treatment of
small cavities, such as those resulting from the
decay of stubs. The treatment of one form of
rotten stub, for which tin is especially well
adapted, is indicated by the accompanying draw-
ings. Metal does very well as a covering for the

TREATMENT WITHOUT FILLING 193

oval cavities resulting from the partial healing and
partial decay where a limb has been torn away by
the roots, as so often happens in elms and silver
and red maples. It is often the best way to
handle the top of a chimney cavity. It is all
right for cracks which do not open and shut. It
is not suited to the treatment of large, long, and
contorted cavities.

In several different connections, I have spoken

Hollow stub cut off close and covered with tin

of decayed trees which could not or ought not to
be cleared entirely of rotting wood. There are
two reasons why this may be the case. First, the
decay may be of such a character, and may have
spread to such an extent, that its complete removal
would involve a prohibitive expense. Second,
for similar reasons, the complete removal of the
decayed wood (retaining, as it does, a certain de-
gree of strength for many years), and the re-
moval of large amounts of sound wood in getting
at the decay, may promise to involve a greater
risk of damage than is involved in the presence

i94 PRACTICAL TREE REPAIR

of the decay. The basic principle we have so far
been working on is that the purpose of cavity work
is to stop decay, and that decay can be stopped
only by the complete excision of the contaminated
wood. Is there anything, then, which can be
done if complete eradication is impossible? To
this question, I believe, an answer, provisional
perhaps, can be made in the affirmative. Decay
undoubtedly progresses at different rates under
different conditions. Weather, moisture, and in-
sects favor the destruction of wood by decay; dry-
ness and freedom from the attacks of insects re-
tard most types of decay. Many rot-producing
fungi work so slowly that the infested wood re-
tains a fair amount of tensile strength and a very
considerable amount of compressive strength for
a great many years. It is worth while to prevent,
as long as possible, the complete disintegration of
this dead wood through the activity of insects and
of " follow-up " fungi and bacteria. As to this
last point very little is definitely known, but it is
probable that bacteria are very important in the
final bi caking down of decay-infested wood.
Moisture, it is well known, is essential to the
growth of bacteria, as of other fungi.

There are times, then, the writer believes, when
it may be profitable simply to treat a cavity so
that insects and moisture may be kept out in so far
as is possible, and that the conditions may be

TREATMENT WITHOUT FILLING 195

made as unfavorable as possible for the growth
of fungi and the oxidation of wood. There are
several ways in which to go about the application
of this principle. The first step is to remove all
loose decayed wood, and to impregnate the re-
mainder with a moisture-repelling preservative
such as hot carbolineum. In order to do this
effectively, it is usually necessary to let the cavity
dry for a few days, or else to char it out with a
gasoline torch. If the carbolineum is brushed
on it must be dashed into all the cracks. At least
one coat should be sprayed on, if possible. The
first thing to be attended to, however, is the drain-
age of the cavity, if it needs draining. An in-
cision can be made to accomplish this, or, if there
is a " pot " to handle, the decayed wood in it can
be cut and burned out, and it can be filled with
stones and asphalt.

If a hole runs up the tree it should be cleaned
out as well as possible, sprayed with carbolineum,
and blocked up in some way. An old sack, or a
sack full of excelsior or straw, the whole thing
dipped in carbolineum, might fill the bill.

If a cavity so treated is located in such a way
that the rain cannot beat into it there need be no
covering over the mouth to keep out the weather.
Indeed, light and ventilation are likely to retard
the growth of the fungus. If the mouth is hori-
zontal, on the other hand, it may be well to tin

196 PRACTICAL TREE REPAIR

over the opening. The tinning, of course, must
be just as well done as if the cavity had been
thoroughly excavated.

For blocking a small hole at the base of a hoi-

Plug of concrete at base of
chimney cavity

low tree, nothing is better than a plug of concrete,
held in place by nails driven into the wood a couple
of inches back from the opening. An incision
must be made, and the filling must be kept back
from the cambium line, just as in ordinary fillings.
It perhaps ha4 better be said again that the

TREATMENT WITHOUT FILLING 197

processes last described are not advanced as the
correct treatment for valuable and historic trees,
but when used in the woods or orchard, where
more effective treatment is economically or tech-
nically out of the question, they are well worth
their cost, if only to prevent the breeding of bor-
ing insects.

CHAPTER XI
BRACING

THE bracing of trees is one of the most im-
portant phases of tree repairing. Most
trees which reach maturity die through being up-
rooted or broken down. If a tree breaks off
bodily the trunk is usually rotten, and rotten
trunks are most often caused by decay entering
through wounds caused by the breaking-off of
branches. Thus bracing may prevent decay.
Even if decay has set in, bracing may put off for
many years the inevitable result of the destruction
of the tree's framework. The vitality of trees is
wonderful. Hollow old apple trees and chest-
nuts which look as if the next strong breeze would
blow them over, will flourish for years. Hollow-
ness does not necessarily mean physiological weak-
ness. Even if the heartwood, which is dead and
mere support, is eaten away, the living, sap-con-
ducting wood may be intact. If, then, we use a
few rods of iron and lengths of wire rope to per-
form the function normally performed by the
heartwood, the tree's "expectation of life" may be
as good as if it contained no decay.

198

BRACING 199

The question of when to brace is not easy to
answer. A limb requires bracing if serious decay
appears in it or in the trunk from which it springs;
if a bad crotch has developed; or if, for any rea-
son, including natural growth, the load supported
by the limb has increased to such a degree in com-
parison with its strength as to make it look, and
be, " dangerous." A tree as a whole may require
bracing if trees near-by which have protected it
from the wind have been removed, if the tree's
foothold has been weakened, if its trunk is de-
cayed, if it has lost large branches and become lop-
sided, or if structures have been placed beneath it
which would make its fall especially disastrous.

Some kinds of trees require bracing oftener than
others. The fruit trees lead, and especially the
apple, with its long horizontal branches. Trees
which form close crotches, as the silver maple and
elm, and weak-wooded trees, as tulip, linden, wil-
low, and some maples, are especially apt to need
preventive or corrective strengthening.

Judgment, careful investigation, and observa-
tion under stress of ice-storm or full crop, must
supplement the above rules as to when to brace.
In any event, the presumption should be in favor
of bracing. It is good insurance, like the stitch
in time. A few dollars' worth of iron, though not
essential now, may some day save you the loss and
sorrow caused by the destruction or mutilation of

200 PRACTICAL TREE REPAIR

a beautiful tree. If you are in doubt as to
whether to use cement filling you may wait a year.
The decay will spread but slightly. But if brac-
ing is needed, do it at once, for the next storm may
wreck the tree. And never depend on cement as
a substitute for bracing.

In coming to the methods of tree bracing, it is

C&rnbivm

fifteenth
\ of cambium.
' remove

ty bolt

Two bands, one now broken, Showing how a bolt put
around limb of a sugar through a limb, kills less
maple cambium than a band

necessary to dispose, first of all, of an old idea on
the subject. It has long been the custom to
strengthen the spreading limbs of old trees, espe-
cially elms, by binding them up with a chain or iron
band, just as one would tie up with a string the
stalks of a sprawling hollyhock. These bands
usually break. If they do not they often break
the limbs they are supposed to strengthen, for they

BRACING 201

kill the bark and stop growth where they impinge
on the limbs, and wear their way far into the wood.
Any brace which wholly or partly constricts the
growth of a limb defeats its own purpose, for it
prevents by just so much the natural strengthening
of the limb. There is no reason why a tree should
have to wear corsets.

The great point is that the nourishing sap, as
we have seen in the second chapter, flows down
the delicate cambium just beneath the bark. If
the cambium is killed, growth at that point ceases,
and decay begins. If a band is used, a strip of
cambium is killed which amounts to from a fourth
to a half of the circumference of the branch. If a
bolt is run clean through the limb, the nut being
sunk into the wood, perhaps a tenth of the circum-
ference of cambium will be removed, and this
amount will be quickly reduced as the nut is grown
over. No system will therefore be proposed which
requires the removal of any considerable amount
of cambium, measured on the circumference of the
limb. Narrow incisions into the cambium made
parallel to the length of the limb heal rapidly and
are comparatively harmless.

Another general principle is that the brace
should be as high up as is possible, or, at least, as
is convenient. This follows from the physical law
of the lever and the fulcrum. A brace near the
crotch has to be much stronger than one which is

202 PRACTICAL TREE REPAIR

farther from the crotch. Light materials can be
used for rather heavy jobs if this principle is em-
ployed.

As a rule the brace should not be pulled up taut.
If chain or wire is used a little slack should be left,
and long rod-iron braces should always be jointed.
The reason for this is that a branch can normally
sag a few inches without danger, and it is only
when this safe elasticity has been used up that the
brace is needed and should come into play. At
this point the strength of the brace is added to the
strength of the limb. If the natural sag of the
limb is not permitted, the brace must assume the
entire strain the moment an unusual burden is
placed on the limb. The amount of slack re-
quired depends, of course, on the distance of the
brace from the crotch. Where the purpose of the
brace is to close up a crack obviously no slack can
be allowed.

Various materials are used for braces. Form-
erly, chain was much used. It has the advantage
of being rather easily applied, if hooked bolts are
used, but is expensive, conspicuous, and easily
rusted. Rod-iron is equally expensive, very diffi-
cult to adjust, often noisy, and requires frequent
trips to the blacksmith's while work is in progress.
Of late years the writer has come to depend on
heavy wire for light work and the various sizes
of steel wire rope for heavier work. This ma-

f

Willow in Longfellow Park. Cambridge, Mass.,

showing how an iron hand constricts the tree. A

bolt through the limb should have been used

BRACING 203

terial is very strong, inconspicuous, and extremely
economical, both of material and labor.

The wire is normally used to connect laghooks
or eyebolts fixed in the branches to be braced. In
large jobs the strength of the wire must be made
approximately equal to the strength of the anchor-
ing material. It is wasteful, for instance, to use
wire rope with a strength of two thousand pounds
to connect eyebolts which have a strength of only
one thousand pounds. A lighter rope should be
used.

The simplest form of brace is a straight bolt
through the trunk of a splitting tree. In the case
of young trees this treatment alone may cure a
dangerous crotch. I shall state with care the
method of inserting such a bolt and in subsequent
descriptions shall take for granted an understand-
ing of the proper way to insert a bolt in a tree.

First decide on the size of bolt to be used, —
a quarter-inch, say, for a four-inch sapling, or five-
eighths for a tree of ten inches or so. Then with
a bit of the same size, bore a hole through the
tree, choosing a place where the wood is thick
and strong, and where the hole will be nearly per-
pendicular to a fairly level and clean surface at
both ends. Now take a chisel and cut out a shal-
low coffer or depression into the wood at one end
of the hole. This coffer is to receive the square
head of the bolt, for machine-bolts and not wagon-

204 PRACTICAL TREE REPAIR

bolts are used. It must be just the size of the
bolt-head and its floor must be at right angles to
the hole, regardless of the bark. It may be shal-
low or deep, but must be sunk through the bark
and at least an eighth of an inch into the wood.

', ^ -. \N(/t&nd washer
\ \ \ sunk in round
\ x , x \coffer ,,,,„],

Diagram of bolt through a limb, and views from above of
both ends of the bolt

If the head is sunk in to the level of the cambium
it will be quickly grown over, but that is an ad-
vantage of appearance only. A similar coffer, ex-
cept that it is round, to receive the washer, must be
made at the other end of the hole. Now run a
wire or stick through the hole and get the length
of the bolt. The bolt being selected or prepared,

BRACING 205

paint it and both coffers with tar. Drive the bolt
through, apply the washer and nut, and tighten
up. If much of the bolt extends beyond the nut
it can be cut off with a cold-chisel or hack-saw.
Now paint all exposed iron, and the work is done.
Some very particular people fill up the coffers, to
the level of the cambium, with putty, plaster, or
cement, but unless they are very large they will
soon be covered by a natural callus.

As a rule a single bolt should not extend through
two branches, even though they be close together,
because, if there is much sidewise movement, or
twist, one of the branches will be split. However,
when the two trunks of a bifurcated tree run up
nearly parallel, the best way to brace them is usu-
ally to put a single heavy bolt through them, not
very far above the crotch.

We will now turn to the bracing of the limbs
of small trees. Apple and peach trees are espe-
cially liable, if not properly pruned, to develop
long branches which are not strong enough to sup-
port large crops of fruit. Such limbs are usually
propped, but bracing with wire is much more satis-
factory. For such work fence-wire, or even bal-
ing-wire, doubled, will do very well, but wire which
is not galvanized must be painted. Large screw-
eyes can be used in the limbs or even more econom-
ical devices can be used. One of these is as fol-
lows: Bore a hole through the limb about twice

2o6 PRACTICAL TREE REPAIR

die size of the wire. Run the wire through, turn
the end and run it back. Adjust a headless ten-
penny nail in the loop so that it will catch the wire
as the loop starts to pass through the hole. The
nail must lie lengthwise of the limb and it is just
as well to cut a slot in the bark to receive it. This

Cross sections through small limbs, showing four methods
of fixing wire

device is usually used with a double wire, but it
can be done with a single wire just as well. Only
two or three inches at the end of the wire is turned
and pulled or driven back into the hole. If it is
a tight fit and the wire is stiff the anchor will be
as strong as if the wire were doubled throughout
its length. Another scheme is to bore two smaller
holes and run the wire in one and out the other.
One hole must be just above the other — say three

BRACING 207

inches away. Another way is to bore two holes
from a single point, one slanting up the limb, the
other down. A slot in the bark from one hole to
the other can be made to receive the wire, but care
should be taken in pounding the wire into place
not to bruise the bark. The nail or wire will be
grown over in a year or two. If the hole is not
filled up by the wire a bit of cloth dipped in tar
might be pressed into it to keep out insects and
fungus spores until growth closes the opening.
Tree-doctors may say these schemes are not work-
manlike, but they are effective, economical, and
easily worked, and they don't hurt the trees.

If there are a number of weak branches they
can be supported from a ring near the center of
the tree. If two weak branches are opposite, with
a strong trunk between them, -a wire can be fixed
to one, run up to the trunk, straight through it, and
down to the other.

In larger work we must substitute wire rope for
wire and eyebolts for screweyes or nails. Wire
rope is made of steel and is not very easy to handle
at first. It is better to begin with one of the
smaller sizes before tackling three-eighths or half-
inch. If you have a job to do with the cable, be-
gin by preparing the holes, coffers, etc., for the
bolts, and get the bolts ready. Then, on the
ground, take the bolt which is to go into the place
at which it is less convenient to work. Run the

208 PRACTICAL TREE REPAIR

end of tKe rope through the eye six or eight inches.
Bend over this end, using the hammer to pound
it down. Then fray out the wire strands in this
bent end. Pull up one strand and bunch the
others down on to the rope. With a pair of pliers
wind the detached strand around the bunch and the

Method of splicing wire rope to eye Two methods of brae-
bolt ing three limbs

rope. When you come to the end of this strand,
take up another and wind it around, and so on to
the last. Now take the bolt, with the cable fixed
to it, up into the tree. Drive it home and adjust
the nut and washer.

It is now time to go to the other end of the
brace. Set the boltjn its final position. Cut off
the rope with a foot or so to spare. With a block
and tackle or a light turnbuckle and " come-along,"
tighten the rope, pulling it towards the eye of the

BRACING 209

bolt. Thread the end of the rope through the
eye and proceed exactly as with the other. When
the tackle is taken away this will leave just about
the right degree of slackness in the wire rope. If
it is desired to put a greater strain on the rope,
the nuts on the bolts can be screwed up only two or
three threads at first and tightened up afterwards.

" Come-along " and turnbuckle arranged for tightening up a
wire rope brace

The only step in this process which requires
special tools is the tightening up of the cable. The
ideal outfit for this work is a long, light turnbuckle
with two hooks, and a lineman's "come-along" to
grip the rope. A grip can be secured in other
ways, however, as by means of one of the smaller
cast-iron (not stamped) tie-plates used by linemen
to splice cables. The middle bolt of the tie-plate
is taken out and a wire is looped through the hole,
the turnbuckle being hooked over the loop. With
the smaller sizes of cable a strong man can get
usually a sufficient degree of tightness, especially if

210 PRACTICAL TREE REPAIR

the limbs are drawn together a bit beforehand.
It is not practicable to lay down rules as to the
sizes of bolts and wire rope to use in particular
cases. About all that can be said is that heavier
material than seven-eighths iron and half-inch wire

Eyebolts and turnbuckle are used to pull together two weak
limbs when the strain is great

rope is not likely to be needed very often. Yet the
strain produced by a long and heavy limb is very
great and it is better to have the braces too heavy
than too light.

If it is necessary to brace a large limb up stiff
to the trunk in order to close up a crack or to take
strain off a cement filling, an iron rod must be used.
The rod must have hooks at each end, to hook over
the eyes of the eyebolts. The measurements for

BRACING 211

the rod and bolts should be made with care and
the entire operation should be planned in advance.
Sometimes it is necessary to put a joint in the rod
in order to make it possible to hook it over the
eyes. The pulling-up can be done by tightening
up the bolts, one of which should be given a long
thread with this in view. Where a greater strain
is required a turnbuckle must be inserted into the
rods.

Considerable ingenuity is often required to find
a proper support for weak limbs when there is no
strong main trunk to anchor them to. The usual
solution is to make limbs on opposite sides of the
tree balance each other. Or, the braces can be
made to radiate from a ring in the center of the
group of limbs. It sometimes happens that the
top of a tree is broken off and that the remaining
limbs, which afterwards grow to considerable size,
are practically horizontal. If such limbs need
bracing, as they are apt to, a rod or tripod must
be set up in the center of the tree to take the place
of the trunk.

In a few cases braces are impossible and props
must be used. The old forked-stick method does
very well for light work, but where a large limb
is to be permanently supported, a stronger device
must be used, and one which is less liable to injure
the bark. The best way is to use a pole with a
short iron rod inserted in the end, exactly like an

212 PRACTICAL TREE REPAIR

ordinary tent-pole. A hole is bored into the
under surface of the limb and the iron rod is
inserted, just as it is into the ridge-pole of the tent.
If it is a tight fit the limb will be able to lift the
prop in a windstorm without danger of the prop's
falling. If the prop extends from one limb, or
one tree, to another, both ends of the prop must
be provided with correct contact points.

Not only do the individual limbs of a tree often
require bracing, but trees as a whole are frequently
so weakened or thrown out of balance that if sup-
port is not given them they will sooner or later be
blown down by storms. The methods in this
work are practically the same as those described
for bracing limbs by the use of eyebolts and wire
rope, except that heavier materials must usually
be used. The main difficulty is to find proper
anchors for the guys. In a grove other trees can
be used, even if they are at a considerable distance.
If no trees are available a short post may be neces-
sary. Telephone and telegraph linemen have re-
duced this kind of work to a science and useful sug-
gestions can be gathered from a study of their
work, though of course they are not bothered by
aesthetic considerations.

In bracing trees, especially from one tree to an-
other, what has been said about the value of a little
slack in a brace must not be forgotten.

Often the principal danger to a tree is from the

BRACING

213

twisting effect of winds. If the conduct of the tree
in high winds indicates that this danger exists, an
effort should be made to correct it by running
braces from a neighboring tree, not to its trunk,
but to its limbs.

Although most bracing consists of bracing limbs
together, occasion sometimes arises for bracing
limbs or trees apart. This occurs when two trees

Showing correct method of propping a weak limb, and three
ways of handling two limbs which rub against each other

or two limbs are so close that they wear against
each other. The general rule in such cases is that
the less valuable of the offenders should be cut out.
Such heroic treatment, however, is often undesir-
able. If so, the thing to do is to brace the limbs
apart. The most obvious way to do this is to pull
the limbs away from each other by means of wires
or rods running to other limbs. Failing this, one
of several other solutions can be used. One way
is to pull the limbs apart, bore a shallow hole in the
worn surface of each, and put in a short iron rod

214 PRACTICAL TREE REPAIR

to hold the limbs apart. Another way is to bore
a hole straight through both limbs and run a bolt
through, inserting a short length of gaspipe over
the bolt between the limbs. This does very well
if there is not much side-swing to the branches.
In that case a different scheme must be used. A
good way is to fix a couple of buffers to the limbs.
They can be of iron if an occasional squeak is no
objection. If it is, one at least should be of
wood.

Bracing even has the unusual quality of some-
times being able to bring the horse back to the
barn after he has been, stolen. After a storm,
especially an ice-storm, we often see a tree fairly
crushed to the ground, though hardly a branch
has been entirely broken away. The large limbs
have been split down at their crotches but are still
attached to the trunk by hinges of more or less
splintered wood and wrinkled bark. It is often
possible to pull such limbs back into place and
save them with but little damage. The work
should of course begin as soon as possible after
the accident. • Each limb should be lifted, with the
help of block and tackle, and, possibly, a tripod of
beams, and firmly braced into place. For this pur-
pose, if much doubt is felt as to whether the limb
will survive the operation, it may be well to use a
temporary arrangement, tying the limb up (pro-
tected, of course, by slats of wood or bandages of

BRACING 215

burlap) with rope, wire, or chain. If there is any
detached bark it should be bound to the wood with
the hope that, even if the bark dies, the cambium
will be saved to form a new bark. All exposed
surfaces should be covered with one of the ma-
terials for preventing drying described in the chap-
ter on wounds. If the leaves wilt badly the tree

Two ways of bracing an entire tree

should be watered (if it needs it) and the injured
branch (but not the whole tree) should be pruned
back more or less severely. If, in the end, one
branch dies, it must be removed and all the wood
which it has detached in the least from the rest
of the trunk must be removed and the wound
smoothed and dressed.

Even whole trees which have been wholly or
partly uprooted can be straightened up and made
to flourish again. Such a process affects the tree
somewhat as transplanting does, and is most suc-
cessful if it happens to be needed during the trans-

216 PRACTICAL TREE REPAIR

planting season. Good soil should be supplied
the replaced roots and the tree should be watered
and pruned, usually rather severely.

CHAPTER XII

THE PREVENTION OF WOUNDS AND
CAVITIES

ENOUGH has been said about the difficulty,
expense, and uncertainty of filling trees to
make almost unnecessary any argument in favor
of protective and preventive measures. And yet
the slowness with which decay does its work, and
the fact that the tree, lacking a nervous system,
may give no indication in one part that another
part is being eaten away, often blinds people to
the danger which lurks in every wound in a tree.
The prevention of decay is vastly the most valu-
able part of the work of tree repair. It pays
back by far the largest return on its cost. It is
the stitch in time which saves nine, and many
times nine.

The work of prevention of decay falls into
three divisions: making those wounds correctly
which have to be made, dressing wounds, and
preventing wounds.

The first phase is really within the realm of
tree pruning. A very large proportion of the
cavities which have to be filled, or which cause the

217

2i8 PRACTICAL TREE REPAIR

ruin of trees, have their origin in the stubs left by
wrongly sawing off limbs. Yet the fundamental
rule of pruning is that every branch must be cut
off close to the trunk or limb from which it is
growing. The cut ought to be made so close
that, seen in silhouette, it is hardly
possible to tell at what point the
branch was cut off. The reason
for this is obvious from our study
of the nature of the cambium and
of the healing process. If the
cut is made close to the trunk the
forming callus is close to the main

fl°W °f SaP* The cambium which

is building the callus is well nour-
ished and does its work quickly.

For the same reason, a main trunk which has
to be cut off must always be cut just above a
healthy limb, and usually not horizontally, but
slantwise, not only so as to shed water, but also
so that none of the remaining bark may be very
remote from the current of sap flowing from the
trunk into the limb. If an adventitious shoot, or
water sprout, should appear at the lower edge of
the cut, its healing will be accelerated.

A limb must be cut off at its actual base, which
is sometimes not the apparent base, as often when
a branch leaves the trunk at an acute angle. If
when a limb is removed the resulting wound is

PREVENTION OF WOUNDS 219

heart-shaped, and a little pocket remains just be-
hind the notch of the heart, the wood in front
of the pocket must be removed with a gouge.
Indeed, a gouge is rather frequently needed to

The apparent base of the limb is
at " A " but the real base is
at " B," where the cut should
be made

supplement the work of the saw in so shaping
pruning wounds that they can heal normally.

Fungi enter wounds mainly through season
checks and at the lowest part of the wound, where
the drying of the bark and the starting of a callus
often expose the wood just below the' bottom of
the cut, and also form a pocket in which water

220 PRACTICAL TREE REPAIR

stands and decay begins. Hartig calls this point
" the Achilles heel of a branch wound." It
should be specially attended to when the wound is
given its second dressing. Similarly, the bark at
the bottom of the opening of a filled cavity should
be notched with a gouge to let the water drain
out of the trough which is pretty sure to be formed
between the bark and the wood.

The rule as to close pruning does not apply to

Pocket above a pruning wound corrected by the use of the gouge

roots. They should be left as long as possible,
if they are in good condition, unless they have to
be cut off very close to the tree. In that case they
should be cut as close to the trunk as possible, if
necessary by using a gouge. The wound should
be carefully dressed. A good material for this
purpose, as well as for longer roots which are very
large, is hot carbolineum. After following this
with a heavier dressing a few shovelfuls of cinders
should be thrown against the root to drain the cut

Small cavity in white oak correctly filled with
concrete

PREVENTION OF WOUNDS 221

surface. All large roots should be cut square
with a saw.

As to the technique of dressing wounds enough
has been said in the chapter on wounds. There
is one aspect of the matter, however, which seems
to fit better into the present chapter, and that is
the systematic treatment of wounds in large
grounds, in parks, and in orchards.

The importance of this work was first brought

Sections and front view showing the dangerous pocket
which forms at the base of a wound, and the way the
bark must be cut to drain it

to the writer's notice a number of years ago, when
he was employed as foreman on a large California
citrus-fruit ranch. The bark of orange and lemon
trees is thin and rather fragile. During the con-
stant plowing, cultivating, and harrowing which
take place in an orchard under irrigation, the
trees, especially the ones at the ends of the rows,
are often barked, even by the most careful drivers.
Prompt treatment of such a wound will usually
result in the growth of new bark over its whole,

222 PRACTICAL TREE REPAIR

or nearly its whole, area. This was explained
to the men and they were instructed as to the
proper treatment of the wounds. At the corner
of each "block" (ten acres) a bottle of shellac
and one of liquid grafting wax, and a bundle of
rags were hung in a tree. When a man barked
a tree he went at once to the nearest outfit and
got the bottles and some rags. Then he trimmed
away the loose bark with his knife, poured out
some of the wax on a bit of cloth, and spread it
(the wax) over the wound. Finally, he bound
the wound with cloth and smeared the cloth over
the wound with shellac. Even the California
sun could not dry out a wound so treated, and
most of them healed perfectly.

Some such system as this should be in force in
every large grounds and in every orchard. For
the most part, however, it will be sufficient to have
a single repair outfit kept, always ready for use,
at the barn or toolshed.

In addition to this emergency treatment, there
ought to be a thorough yearly inspection and treat-
ment of all valuable trees, be they along the street,
or in park, grove, or orchard. The time at which
the yearly round is made is of little consequence.
A fairly complete outfit is essential. A box like
a carpenter's nail box makes a handy arrangement
to carry things around in, the tools on one side
and the dressings on the other. The tools likely

PREVENTION OF WOUNDS 223

to be handy are a pruning saw, preferably of the
meat-saw type, with a blade which can be set at
right angles to the back, making it possible to
take stubs out of crotches; a gouge and mallet;
a sharp knife, and, if borers are to be tackled at
the same time, the wire and other tools recom-
mended in the chapter on insects. Of dressings,
liquid grafting wax (not likely to be used so often,
however, as in emergency operations), shellac,
and tar, paint, or some form of liquid asphalt, will
be needed, and such things like putty, carbon
bisulphide, and the like, as may be needed for
special purposes. Every tree must be carefully
inspected from its roots up. If it is a young tree
and there is high grass growing around it, pull the
grass away, and make sure that the base of the
trunk has not been gnawed by mice. Inspect the
bark, to see if any part of it has been killed by
canker, frost, or sun-scald. Keep a sharp lookout
for sporophores, dull patches of bark, and other
signs of the presence of fungi. Look for borers.
If the tree has been repaired, see that all fillings
and dressings are in good shape. If old pruning
wounds are checking, give them another coat of
paint. If calluses are growing over any of the
wounds, see that borers are not getting into them,
for several kinds of borers make a specialty of
tender calluses. See that cottony plant lice
are not gathering under the lip of the callus, suck-

224 PRACTICAL TREE REPAIR

ing its sap and deforming its growth. Slit the
bark of the calluses.

This last direction may require some explana-
tion. In the second chapter, dealing with the
nature of the growth of trees and the way in which
wounds are healed, it was brought out that growth

Callus slit along the dotted
lines to accelerate its
growth

normally proceeds fastest where bark pressure is
least. It is that very fact which explains) the
growth of a callus. At first the callus grows very
rapidly, but as the bark covering it gets thicker,
growth becomes slower and slower. Finally, the
callus may become " bark-bound," just as a tree
sometimes does. As it relieves a bark-bound tree

PREVENTION OF WOUNDS 225

to cut slits in the bark, so a slow-growing callus
can be relieved by slitting the bark of the callus.
There is this difference, however, that the bark
of the callus need not be bound, in order to profit
by the slitting. Even a rapidly growing callus
of one or two years can be made to grow even
more rapidly by cutting through its bark. In-
deed, I have sometimes cut a callus twice a year,
once in May and again in July, with obvious ad-
vantage. It is really surprising how rapidly a
wound will be healed over, if it is close to the trunk
of a healthy, growing tree, and the callus over it
has its back scratched occasionally with a sharp
knife.

The method of operating is simply to draw the
point of a sharp knife around the callus, parallel
with its edges. The cuts can be made not only on
the inner face of the callus, near the wood over
which it is spreading, but also farther back. The
writer usually uses a number of short cuts rather
than entire circles.

The best way to deal with the question of
wounds in trees, after all, is to prevent the trees
from being wounded. The great majority of
wounds are due purely to carelessness and igno-
rance. They can and should be prevented by in-
telligent pruning, and by protecting the trunks of
trees which are exposed to extraordinary dangers.

If a tree is pruned rationally at not too great

226 PRACTICAL TREE REPAIR

intervals from the time it is set out until it reaches
maturity, the necessity need not often arise for
cutting large limbs. Pruning can also largely pre-
vent the formation of bad crotclres. Both these
ends are attained mainly through care to prevent
the formation of too large a number of branches
from the main trunk during the tree's formative
period. Limbs which wear against each other
must of course be eliminated as soon as they are
noticed.

Bracing is another very important prevention
of the formation of bad wounds, and of splits and
crotches which give the spores of fungi entrance
to the heartwood.

There are a vast number of petty ways in which
trees receive injuries which are entirely unneces-
sary. Such, for instance, as driving spikes into
them to tie the clothes-line to, nailing signs to
them, using them as supports for fence wire and
chicken netting, and setting plank seats between
pairs of trees. These small vandalisms must be
absolutely stopped if the health and beauty of the
trees are to be preserved. A few nails, to be
sure, won't damage a tree much, but they hurt it a
little, and they are a standing invitation to further
maltreatment.

Another large class of wounds has its origin in
bruises to the trunks of trees by tools and wagons.
On the lawn the greatest offender is the lawn-

PREVENTION OF WOUNDS 227

mower, or rather the man behind it. It is as-
tonishing how otherwise good gardeners will com-
placently bang a machine against the trunk of a
tender-barked young tree. On many fine estates
nearly every tree on the lawn bears near its base
the ugly and dangerous memorials of the con-
firmed contempt of gardeners for anything but
their own planting. The cure for such a con-
dition of affairs is not far to seek. Every man
on the place should be impressed with the impor-
tance of avoiding wounds and should be made to
attend immediately to every wound he causes. If
a man proves to be quite unreformable the only
thing to do is to order him to wrap a gunny-sack
around the base of every tree on the lawn before
he starts to mow it.

In the orchard whiffle-trees and cultivator
wheels do most of the damage. Here again,
remedial measures can be effectively applied to
the human element, although short and specially
designed whiffle-trees are an important aid to care-
ful work.

The necessity of placing stout guards around
trees in pastures need hardly be insisted on. The
guards should be of ample size, and so built as to
protect the roots of the tree. Pigs, and espe-
cially boars, are very destructive, and when they
are permitted the run of the orchard the trees
must be protected, either with guards of wood or

228 PRACTICAL TREE REPAIR

poles, or with bundles of thorn branches wired
closely about them.

Trees growing along streams are very fre-
quently hollow, the result of the work of fungi
which enter the trunk through wounds made in the
bark by floating ice during spring freshets. In
bottom lands, trees a considerable distance from
the river are sometimes thus affected. If such
trees are valuable all but the oldest and toughest-
barked must be protected, as by poles tied around
the trunk with wire. The guards can be put on
in winter and taken off in May, or they can be left
on for several years at a time. On a large scale,
it may be necessary to grow willows and birches
to protect the standard trees.

It is in building operations, however, that the
most pitiless slaughter of the innocents takes
place. Graders seem to think only of their
grade, builders only of finishing their work at the
time specified in the contract, and teamsters, one
is forced to believe, of nothing at all. A tree is
either a nuisance to these people, or a convenient
post to which to tie their horses or to nail their
scantlings. The owner does not yet realize the
value of the trees, and is confident that a year or
two of care will remedy the damage they suffer.
But, in fact, the years following building opera-
tions and lawn making are years of low vitality
for the neighboring trees, and they are in no con-

PREVENTION OF WOUNDS 229

dition to have their recuperative powers further
taxed by avoidable bark wounds.

The remedy for this condition of affairs lies in
a wider appreciation of the fact that serious es-
thetic, as well as financial losses can be avoided by
consulting beforehand an expert in the care of
trees, be he an arboriculturist, a consulting for-
ester, or a landscape architect. If it pays to pur-
chase the advice of an expert in heating or light-
ing before building a house — and if that is not
done directly, it is done by the architect, unless he
is an expert in those branches — it will certainly
pay to consult some one, no matter what he may
call himself, who has a really expert knowledge
of trees. An error in handling trees is likely to
be as difficult to remedy as an error in wiring a
house, and may be quite irremediable.

Once the expert is found (often, unfortunately,
not an easy thing to do) he will ask to see the
architect's plans for the grading and drainage of
the lot and for the location of buildings, walks,
and drives. With these, and preferably in com-
pany with the architect and owner, he will visit the
property. There he will examine the trees, not-
ing their species and their physical and physiologi-
cal condition. He will pay special attention to
the soil, its surface covering, its texture, its con-
dition of drainage. After this examination he
will be able to forecast the effect the operations

230 PRACTICAL TREE REPAIR

planned by the architect will have on the trees,
and he will usually be able to suggest modifications
in the plans in order to make them conform to
the needs of the trees. If any of the trees have
to be taken out he will mark those which are least
valuable and least likely to survive under the new
conditions. He will suggest the way in which the
trunks of the trees are to be protected during
building operations, and he will indicate the way
in which limbs and roots must be removed, if that
proves necessary. In addition, it need hardly be
said, he will make very valuable suggestions as to
the fertilizing, pruning, and spraying of the trees.
The ideal way is of course to employ a landscape
architect. He will not forget the needs of the
trees while he is making the grounds convenient
and beautiful.

If the building is to be done by day labor the
owner should see to it that, before a team goes on
the lot, the trunks and roots of the trees are pro-
tected by stakes or rough board guards. It must
be made the duty of the foreman to see to it that
none of his men, nor any of the other workmen or
drivers who come to the place, in any way damage
the trees. If the work is being done by contract,
a brief provision should be included in the con-
tract, specifying that the trees be protected and
that no large limbs or roots be removed without
the approval of the owner's expert adviser.

PREVENTION OF WOUNDS 231

The myriads of woes of the street trees have
long been the subject of lament by the friends of
trees. That street trees in this country should at
the same time be loved and praised so universally
as they are, and so universally maltreated, is a
subject of perennial astonishment. We plant a
thousand trees and promptly murder nine hun-
dred of them. The explanation possibly lies in
our traditional idea, surviving from the period
when we were subduing the forest primeval, that
trees are a good bit like weeds, growing anywhere
and standing any kind of treatment. It is an in-
teresting sidelight on our municipal organizations
that much of the damage to trees is inflicted by
city employees. On one street the department of
street trees will be setting young trees, while in
the next street a gang of men may be chopping
down fine trees which happen to be a few inches
inside of a line laid down by an engineer who has
never been in the neighborhood. The tree war-
den alone ought to be empowered to cut down
trees, or even to remove large roots.

The subject of the protection and care of street
trees has been treated so thoroughly by Dr.
Fernow and Mr. Solotaroff, that nothing further
need here be said about it.

This discussion of the right making and dress-
ing and the prevention of wounds, however, does
not exhaust what is to be said about avoiding the

232 PRACTICAL TREE REPAIR

decay of trees. Sometimes the causes of decay lie
deeper. Its presence may be due to soil exhaus-
tion or to the fact that the tree is growing on a
soil not naturally suited to it. Dr. Haven Met-
calf, forest pathologist in the bureau of plant in-
dustry at Washington, speaking of all the diseases
of woody plants, says : " The most widespread
cause of disease of trees and shrubs is the attempt
to grow them in a climate and situation for which
the given species are not adapted." This, how-
ever, is a subject which is rather within the realms
of horticulture and forestry than of tree repair.
To foresters it is an immensely important matter.
They find that on certain soils decay begins to at-
tack the trees of a certain species at, say, fifty
years, while on a more favorable soil the harvest
can safely be deferred until the trees have stood
seventy or eighty years. The obvious lesson to
be drawn from this fact is that when trees are
planted those kinds should be chosen which are
known to do well on the given soil, and that the
soil around the trees should be kept in good con-
dition.

CHAPTER XIII
THE TRADE OF TREE REPAIR

THE trade of tree repair is as yet in its in-
fancy. It is extremely important that its
growth be strong and fairly rapid. The future
welfare of the trees which are being planted by
thousands in every town and city in the country
depends upon the presence in those towns and
cities of skilled tree workmen. As Prof. Sar-
gent has said, " Time and labor are worse than
wasted in planting unless the after care is intelli-
gent, determined and ceaseless." The following
brief comments on tree repair as a trade are of-
fered not only in order to help, a little, men who
are taking up the trade, but also with the idea of
leading owners of trees to appreciate and use the
services of such men.

The present condition of the trade is in many
ways unsatisfactory, as was explained in the first
chapter. The predominance in the work of a
few large companies is attended by several un-
desirable features. The heavy expense of ad-
vertising, and of transporting and boarding the
men, makes the work more expensive than it need

233

234 PRACTICAL TREE REPAIR

be. It is not easy to have small jobs attended to
promptly. The quality of the work inevitably
suffers from the fact that the men who do it, for
the most part, never see their work again. For
the same reason, the work rarely receives the in-
telligent annual care which is so often essential
to its permanent effectiveness. The men must do
their work quickly and move to the next town.
As a result the processes which require consider-
able time, such as the drying out of a moist cavity,
are pushed through faster than is well. The men
are instructed and hired to do cavity work, and
the other branches of tree repair, especially pre-
vention, are often neglected.

It would be highly desirable if, instead of this
system, there were in every town a man or a
group of men, thoroughly skilled in the work, who
could go from place to place each year and attend
to all of the tree work, and who could be called
upon, in an emergency, by the most modest home
owner. Such a workman would either himself be
familiar with pruning and spraying, or would ally
himself with such men. A man who is really
skilful in repairing, pruning, and spraying trees
ought to find work in plenty, the whole year
round, for himself and one or two helpers, in any
large town in the country.

The first thing a man is up against, naturally, is
learning the trade. As with many other trades,

THE TRADE OF TREE REPAIR 235

there is no regular way to learn to repair trees.
A few months with a good gang will give a man
a fair start, but it is essential that this practical
experience be supplemented by the study of the
many books and government reports bearing on
pruning, plant diseases, and noxious insects. Go-
ing into the woods and chopping rotten trees to
pieces is an excellent laboratory training in con-
nection with this reading. A man who develops
a " tree sense " rapidly, masters the tricks of the
cambium, and is endowed with a moderate amount
of native gumption, will get hold of the work in
short order.

When a man has learned the trade and is ready
to set up for himself, there are several ways in
which he can get into connection with the work.
The old rule that every satisfied client brings an-
other, holds in this as in every other trade and
profession. If there is a professional landscape
architect in the arboricultural workman's home
town, he will be very glad to know of some one to
whom to direct his clients. Landscape architects
of other cities may also be interested. A card
sent around to the owners of suburban estates, to
the superintendents of cemeteries, and to improve-
ment societies, will start connections which will
quickly lead up to a large clientele.

Every effort should be made to secure regular
clients who wish their trees inspected and given

236 PRACTICAL TREE REPAIR

such care as they require every year. That pro-
cedure is much the most satisfactory, both to the
client and to the workman, and is infinitely better
for the trees.

The successful prosecution of a trade like this
is largely dependent upon the promptness, accu-
racy, and definiteness of the business methods em-
ployed. If a number of different kinds of work
are carried on at the same time, as pruning and
cavity work, the expense of each should be deter-
mined and indicated separately in the bill. Ma-
terials must be separated from labor, and skilled
labor from unskilled. When large cavities are
filled it is highly desirable that the expense of each
be determined. This can be done by keeping a
time-card for each cavity, recording thereon the
time which each man spends on it, and the amount
which is used of each kind of material. These
last details are hot, of course, for the client, but
they are extremely valuable to the workman, be-
cause they help him to estimate the cost of future
jobs of a similar character. A reputation for ac-
curacy in estimates is a valuable asset to a man in
any business.

A few words to the owner of trees about the
trade of tree repair may not come amiss. Of
all the foolish things said about trees, the follow-
ing is one of the most foolish and most common :
" Well, I really have neglected my trees, but this

Ash tree with large cavity correctly treated with zinc

THE TRADE OF TREE REPAIR 237

summer I am going to have the tree surgeons
here, and then I won't have to worry about them
any more." Trees are living things and they
cannot be starved and wounded for years with
the expectation that, with a wave of his fairy
wand, the tree doctor will be able to restore them
to strength and beauty. Trees are mostly tough
and long-enduring, even under artificial condi-
tions, but they cannot absolutely shift for them-
selves. The owner of a number of fine trees
ought, if only as insurance, to have them in-
spected every year. One year not a tree in the
grove will need to have any work done upon it;
the next, a few hours spent in bolting up a limb
over-strained in an ice-storm may save a beautiful
tree from irreparable damage. An expert will
detect signs of soil depletion or of the presence
of insects which completely escape the eye of a
layman.

Granted that this is the logical way to care for
trees, how is the program to be carried out? The
vital difficulty lies, of course, in finding men to do
the work. The demand for men will be met,
however, when it becomes intelligent and wide-
spread. Owners should realize that it is to their
own advantage to develop local arboricultural
workmen, just as it is an advantage and economy
to have plumbers and steam-fitters within a
reasonable distance.

238 PRACTICAL TREE REPAIR

By this I do not mean that inferior work should
be accepted from local men. There is no neces-
sity for that. If owners learn to know good
work, and set a high standard, they will receive
good service. In case of doubt about a man,
have the nearest landscape architect or profes-
sional arboriculturist examine him and his work.

Finally, a word to landscape architects. Your
advice is worth nothing to your client unless it can
be carried out at a reasonable expense. It is to
your interest, as it is to your client's, to be able to
refer him to a skilful and reliable man, competent
to carry out the measures you recommend for the
care of his trees. You ought to use every effort
to get into touch with such men, and to help them
when you find good ones. Give them freely of
your special knowledge. Try to develop a corps
of a rbori cultural and horticultural workmen upon
whom you can depend as implicitly as the mem-
bers of your sister profession, architecture, de-
pend upon their carpenters and masons.

CHAPTER XIV
NOTES ON THE VARIOUS SPECIES

IN the preceding chapters trees have mainly
been considered in general, the different spe-
cies having been rarely mentioned. The various
kinds of trees, however, are subject to different
diseases and to different kinds of injury. These
special needs demand special treatments. The
present chapter consists of an alphabetical list of
the commonest trees, with notes on the special
characteristics, important in tree repair, which dis-
tinguish each kind. These notes are intended
simply to indicate additions to or exceptions from
the general rules previously laid down, and are in
no sense complete guides to the treatment of the
varieties concerned. If in a few cases these limits
seem to have been exceeded, it is because the
temptation was great to make this chapter a catch-
all for facts and opinions which did not seem to
fit in anywhere else.

APPLE

The name of the enemies of the apple is legion.
Half-a-dozen fungi are common destroyers of its

239

240 PRACTICAL TREE REPAIR

heartwood, the omnipresent white heart rot being
foremost among them. The honey mushroom
often infests the roots of the tree. Several bark
rots and cankers are ever ready to complete the
destruction of a weakened patch of the bark. Its
insect enemies are no less numerous. Round-
and flat-headed borers attack its heartwood and
sapwood. Bark beetles girdle and kill the trees.
The apple is one of the commonest and one of
the most difficult subjects to come under the care
of the tree repairer. There are several reasons
for that fact. In the first place, the apple is nat-
urally very subject to the attacks of fungi and
borers, as has been shown by the above enumera-
tion of a few of its principal enemies. And it
seems as if man had made every effort to help the
fungi get at the apple's heartwood. When the
young tree is planted too large a number of
branches are permitted to grow out from the
trunk, and they are altogether too close together.
When the tree reaches maturity each of these
limbs has become long and rambling, with a shock
of branches and twigs at its etnd. To the lowest
tier of these limbs one of two things usually hap-
pens. The limb may be killed by bark canker or
blight, or by being overshaded as the trees in the
orchard grow together. In the1 course of time
the owner removes the dead limb. Its butt is
often so closely squeezed in between other limbs

NOTES ON THE VARIOUS SPECIES 241

that he rarely makes a close cut, even if he knows
that he ought to, and a stump or snag remains as
an open gateway for the fungi. If the lower
limbs do not die they are frequently torn out by
wind- or ice-storms, assisted by the natural lever-
age of the long horizontal limbs. The trunks
and limbs, also, of these old, woody, slow-growing
trees, push out calluses very slowly, and on them
even small wounds are dangerous. Still further,
these are the very trees which are most subject to
injury, standing as they do near drives or barns or
in the orchard, where wagons and tools run
against them, and horses lunch on their juicy
bark.

All of these influences, taken together, explain
the gaping cavities which are seen at every hand
in an old, neglected apple orchard.

Almost equally numerous are the considerations
which make us wish to preserve the old trees.
They are highly picturesque, and they give to the
new house which happens to be built among them
an immediate atmosphere of homeliness. They
make excellent shade trees, and are very beauti-
ful in bloom. Their fruit is often fair in quality
and quantity, and there is a perennial hope in the
human breast that both will next year be greater.
Finally, the apple tree is one of the best loved of
trees, and the associations which gather around a
veteran Baldwin or Rambo may far outweigh

242 PRACTICAL TREE REPAIR

other considerations which make the tree valu-
able.

Naturally, then, more apple trees have received
repair work and cavity treatment than any other
kind of tree. It is the purpose of the present
paragraphs to enquire into the value of fillings in
apple trees, and to try to formulate rules which
may govern their use, and also to point out the
special preventive measures which ought to be
used in the prevention of cavities in apple trees,
and the measures other than filling which are
applicable.

In the first place we must distinguish the three
reasons which exist for filling holes in apple trees.
First, the trees may be filled simply for esthetic
effect, decay being considered unpleasant by most
people, on account of the popular association of
decay, even in trees and buildings, with human
death and disease, unless the decay is accompanied
by an extraordinary degree of picturesqueness.
Secondly, the trees may be filled to preserve them
as ornaments to the home grounds or on account
of their sentimental value. Thirdly, they may
be filled to preserve them for their economic value
as fruit producers.

Of fillings inspired by the first purpose it need
only be said, what may seem superfluous, that, in
case the entire elimination and prevention of de-
cay and the restoration of the tree are decided to

NOTES ON THE VARIOUS SPECIES 243

be impossible, and the holes are yet filled, simply
for the sake of appearances, many of those pre-
cautions and measures which are indispensable to
an ideal operation need not be taken. The proc-
esses to be omitted and the short-cuts which can
be used will suggest themselves to one who under-
stands the principles upon which the work of fill-
ing is based.

When the second purpose dominates we may
presume that the factor of expense is practically
negligible. It is safest, however, for the work-
man to warn the owner, before he begins, of the
probable expensiveness and doubtful value of the
work, if the decay is so advanced as to make suc-
cess problematical. Then let him go ahead and
do the very best job that skill and good materials
will turn out. And he must not fail to see to it
that the repair work is supplemented and given
the best chance of being successful by careful prun-
ing, spraying, and such soil treatment as may be
necessary.

With the consideration of the value of cavity
work in apple trees whose sole value is economic,
we come to a very different subject. Here the
factors are more tangible. Costs must be figured
carefully in relation to returns. Expenditures
must be fairly sure to accomplish the purpose for
which they are made.

After considerable experience and observation,

244 PRACTICAL TREE REPAIR

and after many interviews with men who have
studied the matter carefully, the writer has be-
come strongly of the opinion that fillings of even
moderate size cannot be put into old apple trees at
an economic profit. This conclusion is based on
the following reasons.

1. Filling has no effect on fruit bearing.
Those measures which do affect bearing should be
tried, and their success should be assured before
the trees are filled.

2. The value of old apple trees is at best very
slight. They have often exhausted their soil,
which can with difficulty be restored to good heart.
Their tops contain hut little healthy bearing wood.
They are often infested with scale and fungous
diseases.

3. The fillings are by no means certain to ac-
complish their purpose of stopping the course of
decay. The reason for this lies* in the ease with
which insects and decays attack the apple tree,
and especially the susceptibility of apple bark to
decay. There is also the difficulty of completely
eradicating the decay, if it has worked up into the
limbs. The heavy strain put upon the filling by
the leverage and swaying of the limbs, and the
slowness with which old trees build calluses, also
conspire to make peculiarly difficult the filling of
old apple trees.

This matter of the restoration of old orchards

NOTES ON THE VARIOUS SPECIES 245

to profitable bearing is now very much talked
about. The impression seems to prevail that no
tree is so bare-limbed and decayed but that it can
be restored to bushy, .fruitful vigor. It may be
true that there is hardly a tree which cannot be
improved by pruning and fertilizing, but the po-
mologists of the Ohio Experiment Station, who
have studied this matter carefully, assert that re-
juvenation cannot be a commercial success when
practised upon trees more than thiity or forty
years old, upon trees in an advanced condition of
debility and decay, or upon trees with long, bare
limbs and high, thin tops. It costs more to bring
such trees back into bearing (if it can be done at
all) than it does to plant young trees and cultivate
them until they become profitable.

If an attempt is made to restore vigor to apple
trees which contain large cavities, the success of
the restorative measures should be assured, as
has been said, before the filling is done. In most
cases the open system of wound treatment, in-
volving cleaning, draining, and dressing, but not
filling, is preferable to filling.

It may be well to append here a sketch program
for restoration work upon old apple trees, even
though this one may not be much unlike programs
which have been suggested in other connections.
The first three processes should be carried out im-
mediately.

246 PRACTICAL TREE REPAIR

1. Attend to the soil, giving it such cultivation,
fertilization, drainage, or mulching, as it may re-
quire.

2. Spray at such seasons and with such mate-
rials as may be indicated by the fungi and insects
attacking the tree.

3. Prune. Normally a severe heading-back
will be beneficial, but the operation must be modi-
fied to fit the case in hand.

4. Brace weak limbs.

5. Treat wounds.

6. Fill cavities.

BEECH

The beech is subject to the attacks of many
fungi. It is one of the favorite hosts of the white
heart rot, the worst enemy of deciduous trees.
' Wherever any considerable amount of beech
timber is found," say von Schrenk and Spaulding,
" white heart rot is prevalent. In some sections
as many as ninety to ninety-five per cent, of the
beech trees of merchantable size have been found
affected with this disease."

The beech tree is rather tenacious of life, how-
ever, and the decay may fill its trunk for several
decades before the tree succumbs.

No special directions are necessary for hand-
ling the excavation. The bark around the edges
of the cut is a little more liable to dry out than in

NOTES ON THE VARIOUS SPECIES 247

the case of some trees, and care must be taken to
keep it shellacked or waxed.

A mature beech grows so very slowly that the
production of callus is often quite negligible. I
have seen cuts in positions normally favorable to
callus growth where a callus of barely a quarter
of an inch had developed in four or five years.
In such old trees the filling should be put in with
the idea that it must be effective without the help
of a callus-covering over its edges.

The beech is extremely touchy as to soil
changes, and especially to an increase or diminu-
tion of the water supply. In case a serious
change of that nature takes place the top of the
tree is likely to die back. Remedial measures
should at once be applied to the soil, and the af-
fected branches or portion of the stem should be
removed promptly, or they may form gateways
for the entrance of decay into the surviving parts
of the tree. The cuts thus made should be
dressed with the greatest care.

Some types of beech are much easier to work
in and prune than others. There is a pronounced
type in which the limbs leave the trunk at a sharp
upward angle, forming many bad crotches. Such
trees seem more subject to decay than the normal
type, in which the limbs leave the trunk at right
angles. The upright limbs persist, when they
die, much longer than do the horizontal limbs,

248 PRACTICAL TREE REPAIR

thus giving fungi a better opportunity to gain en-
trance to the trunk.

The beech does not react well to the severe
pruning system of rejuvenation, unless the re-
maining framework is well clothed with twigs.

BIRCH

One of the problems in connection with work
in the white-barked birches (as well as other
genera which have white or light bark) is the
avoidance, in so far as is possible, of disfiguring
applications, such as tar and asphalt. On such
trees white-lead paint of the right color should
be used, if the tree is conspicuously placed.

Arboriculturists are frequently asked what can
be done about the ugly black scars which result
from peeling off rings of the white outer bark.
There is no cure for such a wound. An applica-
tion of varnish immediately after the infliction of
the injury might prevent to some degree the
cracking of the exposed inner bark. The black
band can of course always be painted white, which
is advisable, especially when the tree, though
within view, is sufficiently far away to prevent the
patching from being too conspicuous.

CATALPA

The globular catalpa, Catalpa Bungei, which
is so much in vogue just now, often breaks to

NOTES ON THE VARIOUS SPECIES 249

pieces in summer storms after it has attained fair
size. It is certain to lose large limbs by the time
it attains a spread of twelve or fourteen feet.
Preferably, it should be pruned annually and re-
strained from getting so large. Broken tops can
often be propped up to last out the season. No
effort should usually be made to remedy the trou-
ble permanently. Cut off all the split limbs and
prune the others back severely. In a few years
the top will regain size and symmetry.

CHERRY

The black-knot which infests cherry trees and
other stone fruits so widely can be cured only by
complete excision or by the removal of the limb
on which it occurs. The parts removed must be
burned. It has not yet been found possible to kill
the causal fungus by means of any kind of appli-
cation.

In making incisions in the cherry difficulty some-
times arises from the fact that the bark rolls
back from the cut edge, detaching itself from the
wood and drying out. The same phenomenon
accompanies frost cracks and greatly increases
their seriousness in the cherry. The explanation
of course is that the outer bark of the tree is
under tension, and when the opportunity occurs
for it to contract it does so and tears the soft inner
cortex from the wood. A few nails half an inch

250 PRACTICAL TREE REPAIR

or so from the edge of the bark, not driven in too
far, will prevent it from rolling back. In other
cases shallow cuts through the tough outer bark,
parallel to the main incision, may accommodate
the strain, though at a loss to the beauty of the
trunk. This characteristic of the tree should be
remembered when slits are being cut in a trunk
which is supposed to be bark-bound.

CHESTNUT

Sufficient has already been said about the chest-
nut bark disease, and about the foolhardiness of
doing much repair work on trees within the in-
fested or the danger zones.

Even outside of that region (if any part of the
continent can really be considered outside of the
danger zone) it is not a tree which should fre-
quently receive expensive fillings. The chestnut
responds well to the pruning-back process, and
hollow old trunks can be made to support luxuri-
ant, even though not very lofty, tops. In the
main, such old trunks cannot be helped by any
kind of repair work, especially if they are infested
by the red powdery heart rot, Polyporus sul-
phureus. Thousands of dollars have been spent
in trying to excavate and restore veteran trees
affected by this decay, but, in the writer's judg-
ment, with not one chance in a hundred that the
work will prove effective. It seems to him far

NOTES ON THE VARIOUS SPECIES 251

preferable to shorten in the limbs of the tree so
as to take some of the strain off the trunk. If
any work is done upon the hollow trunk it should
be limited to such measures as will prevent the
access of insects to the interior. If a tree repair
man advises filling a tree infested with this decay,
the owner should require a survey to be made of
the trunk, and a vertical section should be drawn,
showing how much of the trunk is invaded. A
prediction should be made, also, of the nature of
the incision which will be required to remove the
decay from the trunk, and from the roots as well,
if it has worked down to the base of the tree.
During the progress of excavation the owner
should see to it that the tree man has been honest
in his survey and thorough in his excavation.

Healthy trees should be carefully protected
from fungi, which usually gain entrance through
dead limbs and wounds in the upper part of the
trunk. It is essential that sickly limbs be
promptly removed and that wounds be effectively
dressed.

ELM

The elm is subject to the usual quota of dis-
eases. One wood rot which the writer has found
rather common in northern Ohio he has not iden-
tified as any of the named fungi described by von
Schrenk and other writers on the diseases of trees.

252 PRACTICAL TREE REPAIR

The wood most recently invaded can with diffi-
culty be distinguished from the healthy wood,
save that it is a trifle " short " and a bit browner.
Wood longer affected becomes soft, moist, and
sour-smelling. The center of the trunk, if the
decay has progressed so far, is hollow, with
webby masses of powdered rotten wood clinging
to the walls of the cavity and heaped at the bot-
tom. It is an extremely unsatisfactory decay to
excavate on account of the difficulty of determin-
ing where it leaves off. A compound microscope
would probably be the only sure arbiter. Bad
cases of this decay are better left alone.

No special notes are necessary upon the treat-
ment of cavities in elms, except to call attention to
the moistness of the wood and the great desir-
ability of permitting cavities to dry out thoroughly
before dressing and filling them. When possible
it is very advantageous to permit the cavity to
stand a month or two with only a preliminary
dressing of some non-filling antiseptic solution
such as sulphate of copper or corrosive sublimate.
If at the end of that time the wood is dry, the
heavier dressings can be applied and the filling
put in.

The elm is more frequently affected than any
other tree by the " slime-flux " which has already
been described, along with such preventive meas-
ures as are known.

NOTES ON THE VARIOUS SPECIES 253

The elm, as is a matter of common observa-
tion, frequently requires bracing, a result of the
manner in which the limbs leave the trunk, or,
rather, in which the trunk breaks into limbs.
Bolts should of course be used in bracing the
spreading limbs of the elm, and never bands or
chains.

HEMLOCK

The hemlock does not often come under the
care of the tree repairer, although the arboricul-
turists of the large public parks may occasionally
have to prescribe for its treatment. It is subject
to a red heart rot (among others) which may be
excised if it has not progressed too far. A care-
ful survey should precede the attempt. Most
fungi probably gain extrance to the trunk through
dead branches, which should be removed if of any
considerable size, even though such pruning may
lessen the picturesqueness of the tree.

HICKORY

Besides an average liability to the general run
of tree difficulties, the hickory is more than nor-
mally subject to becoming bark-bound, on account
of the extreme toughness of its outer bark, which
in pioneer days was used to make barrels and to
roof log cabins. Vertical slits through the outer
layers of the cortex are the remedy.

254 PRACTICAL TREE REPAIR

HORSECHESTNUT

Being a planted tree, there is no reason why
the horsechestnut need often be diseased. It is
occasionally subject to frost crack, which is of
course not preventable. The bad crotches which
so often result in cracks and broken branches can
be prevented by proper pruning while the tree is
young. It should never be allowed to bifurcate
into parallel main trunks, a tendency to which it
is rather subject.

LINDEN

The linden is preyed upon by many rot fungi,
which gain entrance through the many wounds and
cracks to which the weakness of the wood pre-
disposes the tree. Frequently the decay destroys
the wood in the vicinity of the wound through
which it gained entrance, and the top of the tree
is then broken off, leaving a stump perhaps fifteen
or twenty feet high. Such stumps usually send
out adventitious shoots, and develop new tops.
The trunk of such a second-growth top is of
course invariably decayed, and it is a question
whether it is ever worth while trying to remedy
the difficulty. The new limbs should be thinned
out so that they will not squeeze each other, and
they should be cut back occasionally if they get so
long as to overstrain the security of their anchor-

NOTES ON THE VARIOUS SPECIES 255

age to the trunk. The linden sends out adventi-
tious shoots freely, especially if limbs are removed
in winter or very early spring. No old wreck
which is still alive should be abandoned until the
severe pruning method of rejuvenation has been
tried.

Though the wood of the linden is rather frag-
ile, the bark is tough, and limbs which are bent
and fractured by storms, and yet not quite sepa-
rated from the tree, may continue to grow. As a
result of this fact, all sorts of queer and erratic
formations are constantly being observed in an
old linden grove. Many of these spell puzzling
cases for the pruner and repairer. The latter
must often depend on a free use of tar, for to
clean and mend every crack and hole in a large
tree would frequently entail almost endless labor.
In no case should these minor cavities be merely
filled with little dabs of concrete-mortar, as is so
often done by enterprising amateurs. In work-
ing on the linden the best must often be made of a
bad job, frequent reliance being placed upon the
tree's capacity for replacing limbs which are so
badly broken and twisted that they have to be re-
moved bodily.

Nevertheless, unnecessary wounds should be
avoided by carefully bracing valuable trees. In
deciding where braces are needed, the weakness
of the wood should be kept constantly in mind.

256 PRACTICAL TREE REPAIR

BLACK LOCUST

The great fact about the locust, from our stand-
point, is its susceptibility to the attacks of the
locust borer. As a result its chances of long life
are so small that expensive work upon it is not
often justified. There is a yellow heart rot which
gains entrance to the wood through the burrows
of the borers.

MAPLE

The maple, being one of the commonest and
one of the best-loved shade trees, of course comes
frequently under the gouge, so to speak, of the
tree repairer. In the main they involve nothing
more than straightforward work. The red
maple, as has been said, is subject to frost cracks.
The silver maple has an inveterate tendency to
form bad crotches, which must be fought in small
trees by careful training, and its effects must be
negatived as far as is possible in old trees by brac-
ing. The red maple (and perhaps equally the
silver) often shows long shallow wounds in the
upper limbs, the result of the tearing out of minor
branches. The open treatment is usually the best
way to handle these wounds, though good jobs of
tinning can often be done upon them. The red
and silver maples are good subjects for severe
pruning, sending out adventitious shoots very
well. The sugar maple does so less readily.

NOTES ON THE VARIOUS SPECIES 257

OAK

The oak is so typical a tree that almost all of
the general rules apply perfectly to it. The wood
decays slowly and it is possible to make complete
and satisfactory excavations in a larger propor-
tion of cases in working on the oak than on almost
any other tree. The tree is also generally worth
the cost of the work, on account of its longevity
and its power of resisting storms and of accom-
modating itself to changing conditions. When
old it forms calluses slowly and wounds must be
kept well covered. The apparent soundness of
the surface of an exposed area of wood may mask
a considerable thickness of decay just below it.

Though the common supposition that oak limbs
are exceptionally strong is well-founded, in some
cases extra caution must be employed in climbing
oak trees. The long limbs of open-land red oaks
are sometimes so infested with boring insects and
fungous decays, that they snap off without the
slightest warning, though apparently quite large
and strong enough to bear a considerable weight.

SYCAMORE

Sycamores are very frequently quite hollow.
As the tree bears pruning well, it is always wise to
consider the possibility of severe pruning as an
auxiliary to other restorative measures. The

258 PRACTICAL TREE REPAIR

hollow trunks can usually be more effectively
handled according to the open system than by
filling.

TULIP

The wood of the tulip tree is not strong, and
through the frequent wounds resulting from this
fact, decay fungi enter rather easily. Conse-
quently the tulip frequently requires bracing as
well as cavity work. Sometimes the heavy hori-
zontal limbs on open-ground trees fairly break
from their own weight. I have seen such limbs
with dead patches on their upper surfaces a few
feet from the trunk. The wood of the upper part
of the limb had actually been fractured crosswise,
the sap flowing solely through the sapwood and
bark on the under side of the limb. Stiff bracing
and thorough applications of antiseptic dressings
are indicated for this condition of affairs, unless
it is possible to remove the affected limb.

WALNUT

The wood of the black walnut, exceptionally
resistant to decay when seasoned, is not frequently
attacked when in the tree, although sometimes in-
fested by the red and the white heart rots. An
interesting characteristic of the tree is the way in
which the base may be open and quite eaten out,
while the upper parts of the trunk are quite sound.

NOTES ON THE VARIOUS SPECIES 259

WILLOW

The soft wood of the willow (and not less of
its relatives, the poplars and cottonwoods) is
quickly decayed when once exposed to the ele-
ments. Very old willows are rarely sound if they
have been seriously wounded, as they usually are,
sooner or later, by the tearing away of one of
their large branches. Cavity work is rarely
worth while on old and contorted willow trunks,
though it may be quite valuable in the case of
younger trees. Willows grow so fast that
wounds are healed with astonishing rapidity, if
the tree is given half a chance. There is plenty
of opportunity for preventive work on willows,
not letting the limbs crowd each other or form
dangerous crotches, and bracing promptly limbs
which promise to grow beyond the limit of their
own strength. Willows often send out roots
from the side of a wound in the bark. These
roots either work down to the ground or else, if
the trunk is far decayed, spread out in the rotten
wood of the tree's own trunk, thus making the
best of a bad business.

BIBLIOGRAPHY

BIBLIOGRAPHY

Arboriculture, general works

B. E. FERNOW. The Care of Trees. 1911.

WILLIAM SOLOTAROFF. Shade Trees in Towns and
Cities. 1911.

ALFRED GASKILL, J. B. SMITH and M. T. COOK. The
Planting and Care of Shade Trees. New Jersey
Forest Commission. 1912.

Shade Trees. Bulletin 205. Cornell Agricultural Ex-
periment Station. 1907.

Street Trees, their Care and Preservation. Bulletin 256.
Cornell College of Agriculture. 1908.

Shade Trees. Bulletin 125. Massachusetts Agricultural
Experiment Station. 1908.

Pruning

L. H. BAILEY. The Pruning Book. 1898.

A. DES CARS. Pruning Trees. Translated by C. S.
SARGENT.

A. D. SELBY. Dressings for Pruning Wounds of Trees.
Circular 126. Ohio Agricultural Experiment Sta-
tion.

Fungous Diseases

ROBERT HARTIG. The Diseases of Trees. Translated
by WM. SOMERVILLE and H. M. WARD. 1894.
363

264 PRACTICAL TREE REPAIR

SCHLICK. Manual of Forestry. Vol. 5, Forest Protec-
tion. (This book and Hartig's cover diseases due to
soil and climate, as well as to fungi.)

H. VON SCHRENK and P. SPAULDING. Diseases of De-
ciduous Forest Trees. Bulletin 149. Bur. Plant
Industry, Washington. 1909.

Studies of Some Shade and Timber Destroying Fungi.
Bulletin 193. Cornell University Agricultural Ex-
periment Station. 1901.

BENJ. M. DUGGAR. Fungous Diseases of Plants. 1909.

F. L. STEVENS and J. G. HALL. Diseases of Economic
Plants. 1910.

H. VON SCHRENK. Fungous Diseases of Forest Trees.
Year Book, U. S. Department of Agriculture. 1900.

H. METCALF. Diseases of Ornamental Trees. Year
Book, U. S. Department of Agriculture. 1907.

H. METCALF and J. F. COLLINS. Control of the Chest-
nut Bark Disease. Farmers' Bulletin 467, U. S.
Department of Agriculture.

JOHN MURDOCK, Massachusetts State Forester. The
Chestnut Bark Disease. 1912.

Insects

J. B. SMITH. Economic Entomology. Second edition,

1906.

J. B. SMITH. Our Insect Friends and Enemies. 1909.
E. P. FELT. Insects Affecting Park and Woodland

Trees. 2 vols. New York State Museum. 1905.
A. S. PACKARD. Insects Injurious to Forest and Shade

Trees. Fifth Report of the U. S. Entomological

Commission. 1890.

BIBLIOGRAPHY 265

The Bureau of Entomology of the U. S. Department of
Agriculture has published a large number of reports
upon noxious insects including most of the important
borers. They bear such titles as the following:
"The Larger Apple Tree Borers," "Two-lined
Chestnut Borer," " The Peach Tree Borer," " The
Locust Borer and Methods for its Control,'' and
" The Leopard Moth." A list of these will be sent
on request, or the inquirer can describe his wants and
the appropriate bulletins will be sent him. Most of
the State Experiment Stations publish information
about the insects which are locally most injurious.

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