Making a rock garden / by H. S. Adams

ill

DAMS

MAKING A
ROCK GARDEN

THE

HOUSE & GARDEN
MAKING

BOOKS

IT is the intention of the publishers to make
this series of little volumes, of which Making
a Rock Garden is one, a complete library of
authoritative and well illustrated handbooks
dealing with the activities of the home-maker
and amateur gardener. Text, pictures and
diagrams will, in each respective book, aim to
make perfectly clear the possibility of having,
and the means of having, some of the more
important features of a modern country or
suburban home. Among the titles already
issued or planned for early publication are the
following: Making a Rose Garden; Making a
Lawn; Making a Tennis Court; Making a Fire-
place; Making Paths and Driveways; Making
a Poultry House; Making a Garden with Hotbed
and Coldframe; Making Built-in Bookcases,
Shelves and Seats; Making a Garden to Bloom
This Year? Making a Water Garden; Making
a Garden of Perennials; Making the Grounds
Attractive with Shrubbery; Making a Natural-
ized Bulb Garden; with others to be announced
later.

MAKING A
ROCK GARDEN

By H. S. ADAMS

NEW YORK

McBRIDE, NAST & COMPANY
1912

COPYRIGHT, 1912, BY
McBRIDE, NAST & CO.

Published May, 1912

CONTENTS

PAGE

THE ROCK GARDEN . 1

THE CHOICE OF A SITE ... 6

THE WORK OF CONSTRUCTION . .13

PLANTING THE GARDEN . . 24

PLANTS FOR A ROCK GARDEN . .32

THE WALL GARDEN . . . .45

WATER AND BOG GARDENS . . .50

252732

THE ILLUSTRATIONS

AN OUTCROPPING BOULDER CONVERTED
INTO A HOCK GARDEN . Frontispiece

FACING
PAGE

A FLIGHT OF STEPS THROUGH ROCK
WORK 8

AN EXAMPLE OF GOOD ROCK GARDENING 16

A SMALL BIT OF ROCK WORK WHERE
Two PATHS DIVERGE . . .26

FOAM FLOWER AND ONE OF THB
SMALLER FERNS . . . .34

THE ROCK GARDEN BUILT ALONG A
MAIN CURVING PATH . . .42

A WALL GARDEN PLANTED IN COLONIES 46
A FOUNTAIN IN A WALL GARDEN . 50

MAKING A
ROCK GARDEN

Making a Rock Garden

THE ROCK GARDEN

T N Europe, particularly in England, the
rock garden is an established institu-
tion with a distinct following. The Eng-
lish works on the subject alone form a
considerable bibliography.

On this side of the Atlantic, the rock
garden is so little understood that it is
an almost unconsidered factor in the beau-
tifying of the home grounds. There are
a few notable rock gardens in this coun-
try, all on large estates, and in more in-
stances some excellent work has been done
on a smaller and less complicated scale
either by actual creation or by taking ad-
vantage of natural opportunities. But

2 Making a Rock Garden

for the most part America has confined its
rock garden vision principally to the so-
called " rockery."

Now a rockery, with all the good inten-
tions lying behind it, is not a rock garden.
It is no more a rock garden than a line
of cedars planted in an exact circle would
be a wood. A rockery is generally a lot
of stones stuck in a pile of soil or, worse
yet, a circular array of stones filled in
with soil.

A rock garden, above all else, is not
artificial; at least, so far as appearance
goes. It is a garden with rocks. The
rocks may be few or many, they may have
been disposed by nature or the hand of
man ; but always the effect is naturalistic,
if not actually natural. The rock gar-
den's one and only creed is nature.

Rock gardens are of so many legitimate
— in other words, natural — types, that

The Rock Garden 3

there is not the slightest excuse for a
rockery. Even that commonest of ex-
cuses, finding a use for stray stones, falls
to the ground. Any close observer of
nature is familiar with these types. The
natural rock gardens range from the
patches of alpine plants above the timber
line in high mountains down the lower
slopes and through defiles to fields on or
near sea level. Not infrequently they
come down to the very sea, while sweet
waters commonly define and, what is bet-
ter, are now and then incorporated in,
them — here a pool, there a brook. The
bog, too, the heath and the desert, they
take unto themselves, though perhaps only
the nearer edge. And does man, by pon-
derous effort, raise up massive masonry
in orderly fashion ; one day disorder comes
and nature makes things look natural by
another kind of rock garden. Rome's

4 Making a Rock Garden

Coliseum and the ruins of Kenilworth
Castle are only two of the unnumbered
examples of this.

Here, in a nutshell, are not only the
natural variations of the rock garden, but
the inspiration. No rock garden worthy
of the name has ever been created by man
that did not depend upon a study of those
that nature has given the world in prodi-
gal abundance. There were the why and
the how of it all, and man simply saw and
made use of his observations.

The advantages of a rock garden are,
primarily, an element of picturesqueness
that nothing else can provide, and the pos-
session of a place in which can be grown
some of the loveliest flowers on earth that,
if they flourish at all, will never do as
well in the ordinary garden as in condi-
tions more or less approximating their
natural habitat. Also it may be made a

The Rock Garden 5

pleasance of extraordinary attractiveness.
Occasionally — and here is one of the most
important things to be learned about the
rock garden — it is the veritable key to
the garden situation; there are small
places where no other kind is worth while,
if indeed it is possible.

THE CHOICE OF A SITE

rilHE best site for a rock garden is
where it ought to be. That is a sad
truth, for it eliminates some homes from
the game; but useless waste of time will
be saved if this is recognized at the out-
set. First cast your eye about and see
if you have a spot where a rock garden
would look as if it belonged there ; that is
the supreme test. If one does not seem
to belong there, give up the idea philo-
sophically and take it out in enjoying the
rock gardens of other people.

As a rule a rock garden should not be
near the house; it is something savoring
of the wild that does not fit in with most

architecture. Exceptions are when sthe
6

The Choice of a Site 7

house is on a rocky site that makes such
planting desirable, if not imperative, and
a slope from the rear or one side of a
house that seems decided enough to per-
mit of a sharp break in the general land-
scape treatment. Save in these circum-
stances, it is better that it should not be
in sight of the house. This is not so
hard as it sounds ; even on a small place,
the spot is easily concealed by a planting
of shrubbery.

Nor should the rock garden, any more
than the rockery, be in the lawn unless it
is depressed and therefore out of sight,
or mainly so, from the level. The depres-
sion may be a natural or an artificial one,
it may be a brook with high banks or it
may be a sunken pathway. The edge of
a lawn is better, a corner of it is better
yet, and preferable to either is a bank
sloping down from it. The bank on either

8 Making a Rock Garden

side of steps leading from one lawn level to
another is also a possibility to be con-
sidered.

Trees need not be altogether avoided;
sometimes they are essential to the pic-
torial effect. It is not well, however, to
place a rock garden near very large trees.
The drip is bad, especially for alpines,
and the greedy roots not only rob the
plants of nourishment but are very apt
to dislocate the stones.

Somewhere just outside the real gar-
den is the best place; then it is only a
step from one little world into another
that is altogether different. If the rock
garden leads to a bit of wood, either di-
rectly or through a wild garden, there
will be all the more to rejoice over. The
more irregularity the site has, or suggests,
the better ; a rock garden not only should
have no straight lines, but it is not well

Wherever possible make the entrance to the rock
garden a rough flight of steps. Excavate if
necessary. Plant the step crevices as well as
those of the side walls

The Choice of a Site 9

that all of it should be comprehended in
a single view — no matter whether the area
be large or small.

What constitutes a good site is well il-
lustrated by one of the existing American
rock gardens. The place is large, and in
the rear of the house the grounds are level
for a considerable distance and then drop
with a fairly steep bank to a driveway,
below which another terrace leads to a
meadow. Instead of being continuous,
however, the bank above the driveway is
broken by a little glen, seemingly leading
nowhere, but actually an entrance to both
the rear lawn and the formal garden. In
this glen is the rock garden, or rather the
main part of it. Though bounded on the
north — it runs east and west — by the
formal garden and on the south by the
lawn, the rock garden can be seen from
neither of these, nor from the house. It

io Making a Rock Garden

is conveniently near all three, yet dis-
tinctly apart from all. A thin planting
of evergreens screens it on the south and
east sides, and there is a low hedge between
it and the formal garden. The rock gar-
den overflows the glen and runs along the
bank on either side, the shady section be-
ing devoted to an extensive collection of
hardy ferns. Across the driveway there
is more rock garden and then a short
stretch of dry wall garden. Such a site as
this does not have to be found all made.
Given any grounds with a bank, and a
little imagination, and a glen is a mere
matter of shoveling soil. Call it a gorge,
if you prefer. Either, in miniature, is
a favored rock garden form; so are hill
and crest.

Thus far the assumption has been that
the rocks have to be gathered up from
various parts of the place or brought in

The Choice of a Site n

from the outside. But many grounds, es-
pecially those of country places, have the
rocks ; often more than are wanted. Al-
though sometimes this is the best of luck,
now and then the trouble of blasting and
rearranging is about as great as if all
the stone had to be found. It does, never-
theless, make easier the choice of a site;
' where rocks are naturally, there they
ought to be. Occasionally the rocks are
so disposed that there is no choice ; the
site settles itself and it is up to you to
make the most of it.

A single boulder, a few scattered rocks,
or a rocky bank can be converted into a
simple rock garden without moving a
stone. A little judicious planting and the
transformation is complete.

A rock garden with water is a rock gar-
den glorified. Wherever possible, without
injury to the main scheme, the garden

12 Making a Rock Garden

should be brought to the water. Failing
that, bring the water to it, if this is prac-
ticable ; which can be determined when the
site is picked out.

THE WORK OF CONSTRUCTION

QJPRING is the best time to make a
^^ rock garden. When the important
matter of the proper site has been put in
the past, a definite scheme must be
planned. Upon the definiteness of this
scheme, much of the success of the rock
garden will depend. Here desire will have
to be subservient to the situation. It is
not so much what you want as what is
best in the circumstances.

. Do not attempt slavishly to copy the
rock garden of some one else. All the
money in the world would not create an
exact duplicate for you, since nature has
made no two rocks precisely alike. Study
them, of course ; get all the ideas you can.

But study first, and most, nature — more
13

14 Making a Rock Garden

particularly its ways in your own neigh-
borhood. Anywhere there is abundant op-
portunity. Take a leaf or two from the
book of the Japanese gardeners. They
are past-masters of the art of making
rock gardens, with a bit of water thrown
jn. They make use of comparatively few
blossoming plants, but their example is
invaluable Jn the disposition of rocks with
simple effectiveness, in the simulation of
height and distance, in the proper employ-
ment of turf, and in the planting of such
small trees and shrubs as are suitable for
a rock garden scheme. •

Measure carefully the space at com-
mand, and then lay out the plan on cross-
ruled paper. Call each of the little
squares a square foot and the labor will
be made easy. Next, figure out a good
entrance, and, if possible, an equally good
exit — the one invisible from the other.

The Work of Construction 15

Then outline the main path, which should
be as devious as the situation allows, and,
if byways cannot be added, provide for
bays, or more pronounced recesses. Re-
member that you are not merely to simu-
late nature ; you are, by a process of com-
pressing much in little, to epitomize it.

Then comes the selection of the rocks.
Usually the rock close at hand, perhaps
on the very grounds, will answer every
purpose. If you are not fortunate enough
to own any, very likely there is more than
one townsman who will be glad to give
you all the boulders and smaller rocks that
you want, if you will only remove them
from spots where they are not desired.
The cost of removal, even in the case of
boulders of fair size, is not great.

Barring quartz rock, which does not
look well, almost any kind of natural
stone may be made use of to the best

1 6 Making a Rock Garden

advantage. Artificial stone should be
shunned like the plague. Limestone and
sandstone are good materials; granite is
better. Granite, however, does not strat-
ify, and if stratified effects are desired,
another stone must be selected. A good
plan is to use more than one kind, but to
keep them properly apart. Weather-
beaten granite is excellent material, and,
in general, it is well to have the rock look
anything but newly quarried. Pick out
some rocks with a growth of lichen on
them, and be sure that this is not dis-
turbed by the moving.

Boulders may run up to several tons
in weight. Where none is readily ob-
tainable, one can be simulated by in-
geniously combining a few small ones and
concealing the joints by the planting of
such things as stonecrops in earth — which,
save in rare cases of sheer necessity, is

The Work of Construction 17

always used in the construction of a rock
garden in place of mortar.

If the site is level, the next step is to
change all that — first on paper. Unless
the lay of the land is all right at the out-
set, the configuration of the rock garden
must not depend wholly upon the upbuild-
ing; there must be some excavations, but
no depressions deep enough to catch and
hold water just where you will want to
walk.

Aside from the path levels, building be-
gins with the rocks, not with the soil.
This is a highly important point. Place
the boulders first ; they are the big effects.
Aside from that, the heaviest work will
be out of the way. Then start in with
the outlining base rocks. These should
be placed with the largest surface to the
ground and should vary in size. It is
not essential that the lowest rocks should

1 8 Making a Rock Garden

be slightly buried in the ground, but that
course is preferable.

When the paths and outer margins
have been thus defined, scatter more rocks
over the intervening surface, placing them
fairly thick but not close together. Next,
fill in with soil, packing it firmly and
ramming it hard into every crevice. If
it fits in with the day's work, it is not a
bad plan to water the rock work well in
order to pack the soil, and when resuming
the labor on the morrow, to add more
soil, well pressed down, before proceeding
with the second layer of rock.

This second layer should have the rocks
placed with the front edge slightly back
from that of the lower row in order to
form a slope, though an occasional over-
hang may be fashioned if required for a
certain plant known to abhor a drip from
above. The construction then proceeds

The Work of Construction 19

as before, until the desired height is
reached. The height is entirely arbitrary,
but some points should be at least as high
as the line of vision, as one of the great
advantages of a rock garden is the pleas-
ure of enjoying some of the typical rock
plants without stooping. The rocks used
as fillers should overlap here and there
to give strength, but care must be taken
to contrive plenty of long soil runs.
Eighteen inches should be the very least,
A plant like the alpine androsace is a tiny
rosette, seemingly requiring no more than
an inch or two of soil, but its roots are
likely to be found following an earth-
filled crevice in the rocks to the depth of
a yard or so. It is because of this deep
penetration of roots that the soil should
be packed so very firm ; the roots must be,
in no danger of loose soil or of striking
a hidden hollow.

2O Making a Rock Garden

At no point between two stones should
the layer of soil be less than two or three
inches thick after being packed hard. If
an upper stone is likely to bear down too
heavily and crush the plant roots, this

Where a rock would bear too heavily on the one
below it, even with soil between, the pressure
may be relieved by the use of small stones.
The soil run need not be straight, but it must
be continuous, so that the roots of the plant
may find their way from A through to B

may be avoided by placing small stones
here and there in the layer of soil. The
roots will work between these stones, but
there must be a continuous, though not
necessarily straight, soil run from the
front of the rock work to the solid filling

The Work of Construction 21

of earth. The run should slope downward
slightly.

Rocks calculated to simulate a natural
stratification ought to be laid on an in-
cline for proper drainage. Such pieces
of rock may also be employed sparsely in
wedging, and in the making of the so-
called "pockets."

These pockets are of prime importance
in the construction of a rock garden.
They hold the only considerable spaces of
soil and are the chief means of colonizing
plants, thus providing for pronounced
color effects. They should break the
slopes and be irregular in size, shape, and
distribution. The large ones may be easily
subdivided by small stones when the plant-
ing is done if a further separation of
species is desirable. The soil must slope
a little from the top, so that there will
be no standing water.

22 Making a Rock Garden

The drainage of a rock garden is of
vital importance. There must be plenty
of moisture stowed away behind the rocks

Cross-section of rock garden construction, show-
ing shallow (A) and deep (B) soil pockets;
tilting and wedging of rocks (C) ; bridging
(D), and perpendicular crevice soil run (E).
Two to three inches of soil between all joints.
The lowest rocks are partly buried

against the heat of summer, but all excess
must be carried away. The garden should
drain naturally, as the hills do. If any
doubt exists, make a drainage bed of eight

The Work of Construction 23

inches of clinkers before starting to lay
the stones.

The soil should be a good loam with a
little peat, and stones varying in size from
a mustard seed to an almond. A little
manure may be used, but it must be old.

PLANTING THE GARDEN

fTlHERE are two ways of planting a
rock garden. One is to do all the
crevice planting along with the building,
and the other, of course, is to defer every-
thing until the rocks are in place and the
soil thoroughly settled.

The former plan is a singularly appeal-
ing, as well as practical, one. There is
something fascinating in finishing com-
pletely a part of the work as one goes
along. The practical advantage lies
chiefly in the fact that by this method
good-sized plants may be firmly estab-
lished in crevices at the very outset. The
soil in that case should be put part way
in the crevice and packed down. Then

some loose soil sprinkled on top, and the
24

Planting the Garden 25

plant, with the earth well shaken from
the roots, unless it has a tap root, laid
down horizontally with the crown just out-
side the edge of the soil. Next spread the
roots to follow the soil run; fill up the
crevice with more soil, packed well, and
follow with more plants of the same kind.
Use small stones to wedge plants where it
appears necessary. Plants that hang
down should be placed in the higher crev-
ices; this must be all thought out before-
hand.

As a matter of fact, the planting plan
cannot be too thoroughly thought out in
advance. At point after point it dove-
tails with the structural plan, which must
accord with the requirements of what
may be called the more difficult rock plants
— the alpines, some of the ferns, and those
plants that fit in well with rock work but
demand more than the ordinary garden

26 Making a Rock Garden

moisture. The best way is to decide what
plants are most desirable in the circum-
stances, omitting, as a rule, the difficult or
" finicky " ones ; there will be plenty of
time to experiment with those when you
have more experience. Make a face plan
of the several sections of the rock work
and mark on it where the plants are to
go. Use numbers, each corresponding to
a species.

The general idea is that all the soil shall
be concealed, not necessarily at the mo-
ment of planting, but at the end of one
or two seasons' growth. Unless you are
a collector, variety is of little importance.
The main thing is that there shall be
beauty as a whole, a few marked seasonal
effects of color with massed bloom and
some green the year round; the garden
must never be bare at any time, as nature
will show you. Plants clustered here and

Planting the Garden 27

single there is a good planting rule. Colo-
nies, always of marked irregularity, ought
to merge into one another, but they should
not so overrun the rock work that no
stones are in sight. Not infrequently
some of the best effects are obtained where
more rock than flowers is seen. A boulder,
for example, calls for the contrast of
plants, perhaps only a few low-growing
ones in a natural pocket, rather than a
semi-eclipse. As a rule, plant one hun-
dred of half a dozen or so suitable, and
easy, species in preference to fifty or more
kinds.

Study at the same time the form of the
plants that are to be used ; some quickly re-
solve themselves into a carpet, some never
get beyond mere tufts, some always grow
straight up, some prefer to hang down,
and some have foliage that is evergreen
or nearly so. To be more specific, one

28 Making a Rock Garden

plant of Saponaria ocymoides will spread
out over four square feet of soil, and thus
fill completely a moderate-sized pocket,
whereas to conceal the same amount of
ground three dozen auriculas might have
to be used. The same is true of the white
rock cress (Arabis albida). So, too, with
a crevice. A single plant of one of the
trailing stonecrops would fill it, perhaps,
when a number of rosettes of the smaller
kinds of house leek would be called for.

Tall plants, like the foxglove, may
sometimes be used, in a small group, at
the end of a bay on the level of the path;
but they are best placed behind the rock
work, as a background, or as dominating
features of the entrance or exit of the
garden. At the entrance or exit such
bold plants make a good bridge between
the rock garden and the outer grounds.
Spreading and trailing plants should be

Planting the Garden 29

placed a foot or more above the path level
and most plants with tufts or rosettes of
foliage. If the path is broad enough some
of the wide-spreading plants may go at
the base of the rocks, but the rule there
is to use those of moderate spread, with
a few tufted plants and some that grow
upright, but are not tall, to lend variety.
When the path is of flat stones, irregular
in both size and placing, this growth
should fill all the soil space — even between
the stones. Such a path will be found
more than worth while, and not as much of
an undertaking as it may seem.

Obvious considerations are that plants
with a decided hankering after moisture
or shade should be favored in the matter
of location, though it is astonishing how
adaptive many of them are.

Do not plant the weak next to the
strong. Unless you are a gardener of

30 Making a Rock Garden

eternal vigilance, the weak will have the
worst of it before you realize what a mis-
take you have made.

Finally, do not forget that planting is
not the end; it is only the beginning — of
planting. So long as the rock garden ex-
ists there will always be planting. Normal
mortality will necessitate some, there will
be thinning out, and time will suggest ad-
ditions and more or less rearrangement.

And with the planting goes on the
continual care, much of which can be done
in the course of the daily walk in the gar-
den, and therefore the loss of time will not
be felt. Water in case of a real drought,
but use a sprinkler, and do not stop until
the ground has been soaked to a depth of
a few inches. Mere surface watering is
bad enough in the ordinary garden; in a
rock garden it is a fatal error, as the
growth of roots near the top of the soil

Planting the Garden 31

leaves the plants in no condition to stand
the full force of the summer sun.

Go over the garden thoroughly once a
year and all the time keep a sharp lookout
for weeds. If the soil is heavy, top-dress
with grit in the fall. Grit is good for
rock plants. Stone chips placed around
a plant will prevent too much dampness
lodging about the collar in winter. Watch
out for weak spots after very heavy rains.

PLANTS FOR A ROCK GARDEN

many plants are suitable for a rock
garden that the range of choice is be-
wildering. In this, as in the laying out
of the garden, advisability takes prece-
dence over pure personal desire, though,
very fortunately, it is often not difficult
to make the two go hand in hand ; a little
intelligent thought helps a lot.

To the beginner, no better advice can
be given than that which applies to the
picking out of the rocks — use the material
which is close at hand. This is not, by
any means, a mere suggestion to follow
the lines of least resistance. It is far
more. In the first place, there is always

an endless amount of beautiful and suita-
32

Plants for a Rock Garden 33

ble plant life to be had without going far
afield. Then again, natural harmonious
effects in your immediate neighborhood
are pretty sure to be appropriate to your
grounds. Finally, you can see for your-
self how things grow, and as for the hardi-
ness of plants, you have it already tested
for you. This refers not alone to the nat-
ural conditions; there is a second wide
field in the gardens — the hardy gardens —
of others, where you can at once choose
from the many and learn whether certain
plants are too tender or require too much
care for your use.

So far as plants native to the immedi-
ate neighborhood are concerned, their
value to the rock garden of the average
person with limited time, who is not ob-
sessed with the idea of growing the rare
and curious, cannot be overestimated.
And they are so many; more than most

34 Making a Rock Garden

realize, and often of an individual beauty
not always appreciated in the bewildering
profusion of the wild but plainly apparent
when an individual, or a little group, is
open to close study in a rock garden. Do
not make the rather common mistake of
thinking that they are too familiar to be
interesting; they are never likely to be.
And, honestly, can you say in your heart
that they are?

For a Connecticut rock garden the
Greek valerian (Polemonium reptans)
must be purchased, unless a neighbor can
spare some from his collection of old-fash-
ioned flowers; there it belongs in that
category. But why should you of Min-
nesota or Missouri deny so beautiful a
flower a place in your rock garden, simply
because you have only to go to the woods
for it ? The English enthusiast brings *
home primroses from the Himalayas, gen-

Native plants are excellent material for the
rock garden. The foam flower ( Tiaretta cordi-
folia) at the top, and one of the smaller ferns
at the bottom

Plants for a Rock Garden 35

tians from the Swiss Alps, and Dryas
Drummondi from the Canadian Rockies
for his rock garden, but he does not fail
to take advantage of some of the common
things near-by — even the " pale primrose "
and the cowslip.

From ferns alone, or from only plants
of shrubby growth, a most beautiful na-
tive rock garden may be made. And add-
ing small flowering plants, or excluding
all else, there are limitless opportunities.
It goes without saying that A's rock gar-
den in Maine will not be like B's in Louisi-
ana ; but there is no law compelling it
to be.

Among the common wild flowers of the
East that take on unexpected new beauty
when transferred to the rock garden are
the celandine (Chelidonium ma jus), straw-
berry (Frag aria Virginica), cranesbill
(Geranium maculatum), toadflax (Linaria

36 Making a Rock Garden

vulgaris), orange hawkweed (Hieracium
auranticum), herb Robert {Geranium Ro-
bertianum), coltsfoot (Tussilago Far-
fara), Solomon's seal (Polygonatum bi-
floritm), foam flower (Tiarella cordifolia),
bloodroot (Sanguinarla Canadensis), and
some of the violets. These are but a few
names, and random ones at that. Some
of them, the coltsfoot, cranesbill, celan-
dine, and toadflax, spread too rapidly, but
by careful watching and not allowing the
seed to ripen, they may be kept within
bounds. There are many such plants that
will take all the room in sight if they are
allowed to, and they must be watched
closely, or else discarded altogether.
Some of them answer a good purpose by
giving the rock garden a quick start, after
which they may easily be reduced or
thrown out altogether. There need be no
compunction about discarding. Certain

Plants for a Rock Garden 37

plants, like certain friends, you enjoy hav-
ing for a visit, but do not care to see re-
main forever and a day.

Annuals as a class are not desirable for
the rock garden; for one thing, the care
of renewal is too great. Biennials are al-
most as much care, but in each case there
will always be exceptions that are a mat-
ter of individual preference. Few, for
example, would have the heart to reject
the dainty little purple toadflax of
Switzerland (Linarla alpina), just be-
cause it is a biennial. The main depend-
ence, however, must be placed on peren-
nials— the plants that, barring accidents,
last indefinitely. These should be mostly
species; if horticultural, do not use the
bizarre — Darwin tulips, for example, or
the Madame Chereau iris. Nor, with rare
exceptions, should double flowers be used.
A double daffodil looks horribly out of

38 Making a Rock Garden

place, while the double white rock cress
(Arabis albida) will pass.

The easy rock garden plants, where the
material is not taken from the wild, are
to be found in most of the large hardy
gardens of the East. Some of them are
natives of Europe or Asia, and more than
is commonly suspected are at home in
other parts of the United States. Among
the best of these for carpets of bloom are
Phlox subulata, Phlox amcena, Aubrietia
deltoidea, maiden pink (Dianthus del-
toides), blue bugle (Ajuga Genevensls),
white bugle {Ajuga reptans}, woolly
chickweed (Cerastium tomentosum),
creeping thyme (Thymus serpyllum},
dwarf speedwell (Veronica repens), Sa-
ponaria ocymoides, alpine mint (Cala-
mintha alpina), and pink, white, and yel-
low stonecrops (sedum). All of them
fairly hug the ground. There are other

Plants for a Rock Garden 39

plants that form a carpet of foliage, but
the flower stalks rise higher. These in-
clude white rock cress (Arabis albida),
the permissible double buttercup (Ranun-
culus acris ft. /??.), the also permissible
double German catchfly (Lychnis vis-
caria), another double flower, " fair maids
of France " (Ranunculus aconitifolius),
Carpathian bellflower (Campanula Car-
patica), grass pink (Dianthus pluma-
rius), Iris pumila, crested iris (Iris cris-
tata), Christmas rose (Helleborus niger),
Phlox divaricata, Phlox ovata, Phlox re-
pens, foam flower (Tiarella cordifolia),
Veronica incana9 Alyssum saxatile, Saxi-
fraga cordifolia, and various avens
(geum).

Several of the primulas give a like ef-
fect if the planting is close — as it should
be in a pocket. The best are the Eng-
lish primrose (Primula vulgaris), cowslip

40 Making a Rock Garden

(P. veris), oxlip (P. elatior), bird's eye
(P. farinosa), yellow auricula (P. au-
ricula), P. denticulata, and P. Cor-
tusoides. Similarly, spring bulbs may be
employed ; plant them, for the most part,
under a ground cover so that the soil will
not show when they die down. Of the
tulips, single ones of the early and cot-
tage types may be used, if in a solid color,
but most to be preferred are the species,
such as the sweet yellow (Florentine) tu-
lip of Southern Europe and the little lady
tulip (Tulipa Clusiana). Crocuses are
also best in type forms, and the small, sin-
gle, yellow trumpet kinds are the finest
daffodil material. Single white or blue
hyacinths may be used, but better than
the stiff spikes of bloom of new bulbs will
be the looser clusters of bulbs that have
begun to " run out " in the border. Other
valuable bulbs are the snowdrop, Scilla

Plants for a Rock Garden 41

Sibirica, glory-of-the-snow ( Chwnodoxa
Lucilice), guinea-hen flower (Fritillaria
Meleagris), grape hyacinth (Muscari bo-
tryoides), Triteleia uniftora, Allium
Moly, and the wood and Spanish hya-
cinths (Scilla nutans and campanulata).
Taller plants that may be worked in,
oftentimes best with only a single speci-
men or small clump, are autumn aconite
(Aconitum autumnale), Yucca filamen-
tosa, leopard's bane (doronicum), single
peonies (either herbaceous or tree), Ger-
man, Japanese, and Siberian iris, as well
as the yellow flag (Iris pseudacorus), sin-
gle columbines, Anemone Japonic a, Heme-
rocallis flava, Sedum spectabile, Dielytra
spectabile, Dielytra formosa, Jacob's lad-
der (Polemonicum Richardsonii) , fraxi-
nella, Anthemis tvnctoria, single Campa-
nula persicifolia, Campanula rapunculoi-
des, Campanula gloinerata, globe flower

42 Making a Rock Garden

(trollius), snapdragon (antirrhinum),
platycodon, lavender (where it is proven
hardy), and musk mallow (Malva mos-
chata).

Of the lilies, Lilium Philadelphicum, L.
elegans, L. speciosum, and L. longiflorum
are all desirable, and they thrive in partial
shade, though in Japan L. elegans will be
found standing out from the rocks in full
sunshine. For peering over into the rock
garden, rather than being placed in it, L.
Canadense, L. tigrinum, and L. superbum
are recommended.

The pick of the low shrubs are the
charming Daphne cneorum, which flour-
ishes better for being lifted above the ordi-
nary garden level, and Azalea amcena.
The latter, however, should be so placed
that its trying solferino does not make
a bad color clash. Rhododendrons and
mountain laurel fringe a rock garden well,

Plants for a Rock Garden 43

and with one trailing juniper (Juniperus
procumbens) will provide a great deal of
the refreshing winter green.

Single roses, the species, fit in well
where there is room for them. Good ones
are R. setigera, R. rubiginosa, R. Wichu-
raiana, all rampant, and the low R.
blanda. The roses would better be at or
near the entrance or exit, or far enough
above the rock work not to ramble over
small plants.

The plants in this list cover all seasons
and vary somewhat in their soil and mois-
ture requirements. But the variation is
nothing beyond the ordinary garden
knowledge. Most will do better if their
preferences are considered, but none is apt
to perish with average care.

Alpines, as a class, would better be left
to the amateur with the time, money, and
disposition to specialize. Most of them

44 Making a Rock Garden

take kindly to being transferred from a
mile or more up in the air to sea level;
the edelweiss, for one, grows here readily
from seed, and the exquisitely beautiful
Gentlana acaulis thrives in American rock
gardens. But, on the whole, alpines do
not do as well here as in England, where
the summer climate is not so hard on
them. When they flourish here, it is at
the cost of a great amount of professional
care.

THE WALL GARDEN

A WALL garden is a perpendicular
rock garden. But whereas a rock
garden is of all things irregular, a wall
garden has regularity. The wall need not
be a straight line; it is better that one
end should describe a curve, and rocks at
the base may give it further irregularity.
Yet it can never quite lose the air of
man's handiwork. The prime object of
the gardening on it is to reduce this air
to a minimum.

The way to make a wall garden is to
build a dry wall of rough stones — that is,
a wall without mortar. Instead use soil
and pack it tight in every crevice as well
as behind the stones, which should be tilted
back a little to carry water into the soil.

This tilting may be accomplished with
45

46 Making a Rock Garden

small stone wedges. The best kind is a
five-foot retaining wall, as there is then

Planting plan of dry wall, the dark portions rep-
resenting the chief earth-filled crevices. The
plants are: 1 — Arabis albida; <2 — Alyssum saxa-
lile; 3 — House leek (sempervivum) ; 4 — Viola
tricolor; 5 — Armeria maritima

a good body of soil behind to which the
roots can reach out through the crevices.
But a. double-faced wall may be made, if
the situation demands it, by constructing
parallel lines of stones and filling in
solidly with soil.

Although the face of the wall in either
case may be strictly perpendicular, it is

The Wall Garden 47

better that each layer should recede a bit.
Construct it after the manner of the rock

Dry wall for retaining bank. Cross-section, show-
ing crevices, soil runs and tilting of rocks

garden, laying the stones so that the top
will be level, or approximately so.

In planting also, follow the same rules.
It is better to plant as the work pro-
gresses. Either plants or seed may be
used. If it is seed, press carefully into
the soil in the front of the crevices. Small
seed may be mixed in thin mud and this
plastered on the soil. For a tiny crevice
make a pill of the mixture.

48 Making a Rock Garden

The range of reliable plants that do
not call for special care is not great so
far as the crevices are concerned. All the
stonecrops, the house leeks, Arabis albida,

Double-faced dry wall. A few rocks are used
with the soil filling and here and there one on
top of it

red valerian (Centranthus ruber), aubrie-
tia, Alyssum saxatile, snapdragon, wall-
flower (Cheiranthus Cheiri), Kenilworth
ivy, Viola tricolor, Dianthus plumarius,
and Dianthus deltoides are all very ser-

The Wall Garden 49

viceable. Behind the wall, at the top, a
strip of earth should be left and there a
wider variety of plants can be grown.
Single Marguerite carnations and grass
pinks will form a sort of cascade of fo-
liage and bloom there if planted close to
the wall or in the crevices of the top, and
a similar effect, but much bolder, can be
created with the perennial pea (Lathyrus
latifolius).

If the dry wall is already made, the
crevices can be plugged with soil if care
and patience are used. Even a cemented
wall is not hopeless; here and there the
mortar can be chiseled out and an occa-
sional small stone should be removed.

A wall garden has these advantages
over a rock garden ; it is more easily con-
structed, it is of practical use, and it is
sometimes a possibility where the other is
not.

WATER AND BOG GARDENS

XT EITHER the water nor the bog gar-'
^ den is dependent on rocks. Either
or both, however, may just as well be an
adjunct of the rock garden. They solve
the wet spot problem admirably, permit
the culture of native water lilies, orchids,
and numerous other beautiful plants, and
certainly contribute their share of pic-
turesqueness. If water is lacking, it may
often be introduced at little expense.

In most cases it will be found that some
cement construction is necessary, but not
a bit of it should show. This is easily
managed by building a cement shoulder on
the sides of the pool or stream a little be-
low what will be the level of the water, and
then setting rough stones on that. A
5°

A little grotto with trickling water makes a pic-
turesque break in a wall garden. If shady,
plant ferns generously

Water and Bog 'Qa^en^\',\ \$tt

cement bottom for shallow water may be
disguised by imbedding pebbles and small
stones in the cement before it sets.

Dispose the rocks very irregularly, but

To conceal the cemented bank of a pool or
stream, make a shoulder eight inches or so wide
and about six inches below the water line.
Then place small rocks on the shoulder

they ma}7 be so few as to be mere notes.
Avoid stagnant water, and if mosquitoes
are feared introduce some goldfish. They
like mosquito larvae.

Water lilies and sagittaria — one plant
will do if the pool is small — in the water
and near it, but not in standing water,
Japanese iris, yellow flag, globe flower, and
Lythrum roseum are good selections.

'5^- Mfkittg a Rock Garden

Forget-me-not is one of the finest plants
for the banks. Use the perennial kind
(Myosotis palustrls semperflorens).

The bog garden simply reproduces bog
conditions. As a rock garden adjunct it
may be a small spot with the perpetually
moist and moss-covered soil in which the
native cypripediums and pitcher plants
flourish. Eighteen or twenty inches of
suitable soil, a mixture of leaf mold, peat,
and loam, in which has been stirred some
sand and gravel, must be provided. If
an artificial bog, the bottom may be made
of cement or puddled clay.

UNIVERSITY OF CALIFORNIA LIBRARY
BERKELEY

Return to desk from which borrowed.
This book is DUE on the last date stamped below.

MAY 14 1948

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