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Cornell University Library 
SD 406.P4 

Practical tree repair; the physicai repai 
3 1924 002 891 343 , 


Excavating a large ca\itv 








Copyright, 1913, by 
McBride, Nast & Co. 

Published, October, 1913 






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 scie;ice 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 


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- 


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 

To make the book of positive practical value 
the author has overcome the extreme delicacy of 
so many writers in glossing over the names of man- 
facturers and their products. It is his honest con- 
viction that in giving the results of his experience 
that his statements should be put in the most 
straightforward manner possible, without the con- 
cealment of a single detail that may be valuable or 
helpful to his readers. He has no logs to roll but 
merely the desire to educate. 

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. 


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. 



I A Program for Saving the Trees . . i 

II The Tree's Structure and Manner of 

Growth lo 

III Wounds and Their Treatment ... 23 

IV Boring Insects and Their Control . . 53 

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 


Excavating a large cavity Frontispiece 


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

filled with concrete 16 

Wounds caused by lawnmowers 26 

Wounds caused by horses gnawing the bark ... 26 

Frost-crack in black 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 . . 226 
Ash tree with large cavity correctly treated with zinc 236 



Chapter I 

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 


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 


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. 


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 


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 


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," 


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- 


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 


executed. And we need skilled arborlcultural 
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 undertaki;lg 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 


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 


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 


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- 


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 



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. 




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 


cambium which heals wounds and covers over 

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 


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 


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- 
tio;i 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 showi;ig 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 



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 


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 Diagram of the flow of sap 
oval wound 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 



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- 

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 


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 

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 


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 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- 


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 

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- 


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 ajtid 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 


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

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 

■■® 'm>m&3Mz 


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 


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- 


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 


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 


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." " 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 wou;ids. 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 


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 


transverse cut and is then to a certai^i 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. 


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 a.n asphalt 
base, as contrasted with those forms, such as our 
eastern petroleum, which have a paraffine base. 


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


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 


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-proofer 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 


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 " Vamo- 
lene." It costs about eighteen cents a gallon at 

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 


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- 


posed. A final surface dressing is necessary in 
order to protect the cotto;i 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 

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


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, 


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 


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 suiEcient 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 


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 


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 been cleared away and the sound wood has been 

creosoted and tarred 


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 


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 


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 grovs^n 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 o.verlapping 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 



pass, unless a series of mild 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 

through three- 
year-old frost- 


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 


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 bums 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 


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 

Chapter IV 


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 



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 


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 


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

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 


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 


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- 
ambycids, 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- 



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


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 " poplar 
girdler," and the " linden borer." 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 a,n inch wide and hopelessly 
tangled and irregular. The adult beetles come 


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 mo;iths. 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 



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 chest;iut 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. 



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 

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 


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 
larva 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 

The last group of insects worthy of mention as 
wood borers is the horn-tail tribe, or wood wasps. 
The commonest species is the " 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 


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- 
lessa 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 

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 a;iy 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 


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 co;idition, and that the trees 


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 ^letting, tied tight above and heeled two 
inches deep with soil below, make effective pro- 

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 


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 


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 larvs 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 


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 


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 

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 



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 

I - .-- --^A 

Cross-section of maple affected by white heart-rot 


Cross-section of oak showing work of Polyporus 
sulphureus (Bureau of Plant Pathology, Bul- 
letin 49) 


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 hyphse, 
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- 

Although the hyphs 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- 


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 
excision 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 hyphas 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 rela- 
tion of sporophore to 


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 co^iclusive 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 

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 


attack the fruit. The apple blister canker {Nu- 
mularia 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 one of 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- 


retting 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, 1 9 13, 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 an^nual 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- 


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 


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" {Fames 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 


white to light yellowish in color, according to the 
species of tree in which the fungus Is growing. 
When rubbed betw^een 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 sulphureus. 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 on aspen 
(Bureau of Plant Pathology, Bulletin 49) 


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, Armillarta 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 


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 Fames 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 

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


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 alga, 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- 


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 


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 


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 



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. 


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 Fomes 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 

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 


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 


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 


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 


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 


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. 


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- 


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 


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 

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- 


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 


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 is not worth filling 


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 


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 noted 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 

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 


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 

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 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 


always at least a potential cause of the tree's 

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 

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: 


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. 


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


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 

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 


number eleven (weighing a litde 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 

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- 



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 


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 


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 


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 


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 

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 


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 i :4 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 


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 14:8. 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 


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- 

Cavity in the base of a white oak filled with concrete 


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 
amount 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- 


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- 

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 1:2 :4 concrete. At 
the rate of one to four, a bag of cement, three and 


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 4j4 you can obtain the number of bags 
of cement to order, and by multiplying the num- 
ber of bags of cement by 3^, 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 14 concrete con- 
tains approximately .015 of a bag of cement, .016 
cubic yard of sand, and .032 cubic yard of stone or 

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. 


more like wood in its properties, and capable of 
becoming more nearly like an i^itegral 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 


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. 


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 



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 


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 dp 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. 


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. 


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

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- 



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. 


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 


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 


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 is ;iext. 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 


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 



i|/;*g/j.<S»W'y ^"- 


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, 


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 ;iot 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- 


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. 
A;iother 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 

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 


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. 


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 


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. 


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. 


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 


common tools and appliances, and is easily and 
quickly put into the tree. On the other hand, it is 
absolutely u,nlike 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 co;iditions, 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- 



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


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


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 filli;ig, 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, 
readv for filling 


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 conclusiojti. 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 


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 


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. 

Air 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- 


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. 


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. 


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 


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 
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 

Vertical section showing di- 
vision of cement filling into 

ward from in front. 


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. cambium 

Thick tarred roofing ,-^^^^H^__^ 
paper has its advocates, 
however, their theory 
being that it gives the 
filling some elasticity un- 

rlpr rnmnrpQsinn ^he concrete filling must be 

der compression. ^ ^p^ -^^^^ t,^,^^ ^1,^ ^^^. 

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 


back of the cambium depends on the 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- 


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. 


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 

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 


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 


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 

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 


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 


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 do not enhance its beauty. 


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 wdl, 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 


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. 


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- 

with a metal-front • , • j . . • 

asphalt filling '"S P"* "1 ^nd 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 


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. 


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." ^ 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 " 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. 


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. Th? 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 


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 filled 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 




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 
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 comers. The necessary care re- 
quired for fixing the briquettes at the edges of the 

Section showing 
method of 
bonding wall 
and wood 


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 

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- 


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 biace for asphalt- 
briquette Tvall 


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 

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 


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. 


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 

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- 

Chapter IX 

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 t)^e 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 


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


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 difliculty. 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 


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 

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 


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 

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

Dressing __,_^^ 

Sawdust FiHinj 

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 


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 


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 


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 

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 

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 


must be filled up with asphalt or a heavy mixture 
ofi 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 
crow;! 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 


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 


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 of the cavity and of the outer 
surface of the filling may reduce the possibility 
of the entrance of water or of damage resulting 


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 

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 

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


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 


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 

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 
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. 

Braces in hollow split 


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 be left a 


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 ^p"' %Vef "'^ *"" 
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 di<E- 


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 
the decay has proceeded 
farther, it may be com- 
paratively easy to get 
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. 

Vertical section of a hollow 
tree, showing the basal open- 
ing plugged with concrete 
and the upper opening with 
asphalt briquettes. The in- 
tervening space is filled with 


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 


inner wall of the cavity. Over the boards or 
wires any material or combination of materials 
(such as boards, straw, heavy paper, or burlap) 
ca^i 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 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 fiU- 
i;ig 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, can;iot be materially postponed. The ways 
and means of accomplishing these ends constitute 
the subject-matter of this chapter. There are 



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. . . . 


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 co^istitute 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 


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 


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 


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 

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 


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 


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. 


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 one 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. 


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 inroUing 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 ;ioun 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 Lonim m trt iKd hv tin open 
ftystcixi. 1 lie tree wcts bu bdJly damaged by ihe 
leopard moth that it was not considered worth filling 


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 IC 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. 


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 


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 


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 


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 


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, u;ider 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 tru;ik 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 


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 


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 


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 


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 hol- 

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 had better be said again that the 


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 

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. HoUow- 
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. 



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 


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 


-\ Onehilfef 


1 ofc&mbium 
i remofid 

by bolt 
Thro vit limb. 

Two bands, one now broken, 
around limb of a sugar 

Showing how a bolt put 
through a limb, kills less 
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 


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 


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

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 oft 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- 

Willow in Longfclluw Park I, aniljruUe M.iss. 

showing how an iron l)and conbtncts tlie tree A 

bolt through the limb should have been used 


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 

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- 


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. 

HeOid of V 
bolt sunk 
in ■-- \ ^ \ 

coffer \ \ \ \ 

', I '. \Nutt>.nd WMher 
\ \ \ ivnk in round 
\ •. - .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. 


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 


the 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 


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 



end of the 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 brac- 
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 bolt in 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 



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 


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 turnbucfcle 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 


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 puUing-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 

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 


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 
Eesthetic 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 



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 


to hold the hrabs 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 

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 


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- 


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

Chapter XII 


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 



Vertical stub and 
correct cut 

ruin of trees, have their origin in the stubs left by 
wrongly sawi;ig 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 
flow of 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 


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 


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 


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, 


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 


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- 


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 

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 


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 

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 


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 crotches. 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 

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 

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- 

Small cavity in white oak correctly filled with 


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 whifBe-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 


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- 


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 


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. 


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 a;id the prevention of wounds, however, does 
not exhaust what is to be said about avoiding the 


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- 

Chapter XIII 

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 o;ily 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 



be. It is ;iot 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, 


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 readifig. 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 arborlcultural 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 


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 u;iskilled. 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 not, 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 


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 

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. 


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 arboricultural 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 

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 a;id 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. 


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



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 end. 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 the course of time 
the owner removes the dead limb. Its butt is 
often so closely squeezed in between other limbs 


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 ran 
against them, and horses lunch on their juicy 

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 
a,n 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 


other considerations which make the tree valu- 

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 

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 
efi^ect, 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 


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 jwid 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 

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, 


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 but little healthy bearing wood. 
They are often infested with scale and fungous 

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 


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- 


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

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 motH- 
fied to fit the case in hand. 

4. Brace weak limbs. 

5. Treat wounds. 

6. Fill cavities. 


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 


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 bra;iches 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, 


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

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


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. 


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


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. 


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- 

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 


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. 


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, Polyporous 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 


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 


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. 


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. 


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 


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. 


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. 



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. 


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- 


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 

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. 



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. 


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. 



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. 


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 


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


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. 


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. 



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 glv^n 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. 



Arboriculture J general works 

B. E. Fernow. The Care of Trees. 191 1. 

William Solotaroff. Shade Trees in Towns and 
Cities. 19 II. 

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. 


L. H. Bailey. The Pruning Book. 1898. 

A. DES Cars. Pruning Trees. Translated by C. S. 

_A. D. Selby. Dressings for Pruning Wounds of Trees. 
Circular 126. Ohio Agricultural Experiment Sta- 

Fungous Diseases 

Robert Hartig. The Diseases of Trees. Translated 
by Wm. Somerville and H. M. Ward. 1894. 


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, igio. 

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. 


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

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. i8go. 


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.