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  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 Fireplace_; _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 Naturalized Bulb
Garden_; with others to be announced later.


[Illustration: A nearly buried boulder is easily converted into a
beautiful little rock garden. Fill in depressions with soil and plant
there and around the edges of the boulder _Phlox subulata_, sedum,
arabis, etc.]




  MAKING A
  ROCK GARDEN

  By H. S. ADAMS

  [Decoration]

  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




THE ILLUSTRATIONS

  AN OUTCROPPING BOULDER CONVERTED         _Frontispiece_
    INTO A ROCK GARDEN
                                                  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 THE 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


In Europe, particularly in England, the rock garden is an established
institution with a distinct following. The English 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 beautifying of the home
grounds. There are a few notable rock gardens in this country, all on
large estates, and in more instances some excellent work has been done
on a smaller and less complicated scale either by actual creation or by
taking advantage of natural opportunities. But for the most part
America has confined its rock garden vision principally to the so-called
"rockery."

Now a rockery, with all the good intentions 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
garden's one and only creed is nature.

Rock gardens are of so many legitimate--in other words, natural--types,
that there is not the slightest excuse for a rockery. Even that
commonest of excuses, 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 better, 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 ponderous 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
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 prodigal 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 possession 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 conditions more or less approximating their natural habitat. Also it may
be made a 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


The 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 outset. 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 philosophically 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 the 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 permit of a sharp break in
the general landscape treatment. Save in these circumstances, 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 depression 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 side of steps
leading from one lawn level to another is also a possibility to be
considered.

Trees need not be altogether avoided; sometimes they are essential to
the pictorial 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 garden 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 directly 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 that all of
it should be comprehended in a single view--no matter whether the area
be large or small.

[Illustration: 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]

What constitutes a good site is well illustrated 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 is conveniently near all three, yet
distinctly 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 garden overflows the glen and runs along the
bank on either side, the shady section being 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 from the outside. But
many grounds, especially those of country places, have the rocks; often
more than are wanted. Although 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, nevertheless, 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 garden glorified. Wherever possible,
without injury to the main scheme, the garden should be brought to the
water. Failing that, bring the water to it, if this is practicable;
which can be determined when the site is picked out.




THE WORK OF CONSTRUCTION


Spring 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 particularly its ways in your own neighborhood. Anywhere
there is abundant opportunity. 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 in. They make use of comparatively
few blossoming plants, but their example is invaluable in the
disposition of rocks with simple effectiveness, in the simulation of
height and distance, in the proper employment 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 command, 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. 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. Remember that you are not merely to simulate
nature; you are, by a process of compressing 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 advantage. Artificial
stone should be shunned like the plague. Limestone and sandstone are
good materials; granite is better. Granite, however, does not stratify,
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
disturbed by the moving.

[Illustration: Good rock garden planting. Each of the principal species
has a soil pocket to itself. Note the effective background and irregular
crevices]

Boulders may run up to several tons in weight. Where none is readily
obtainable, one can be simulated by ingeniously 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
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 outset, the
configuration of the rock garden must not depend wholly upon the
upbuilding; 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 begins 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 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 overhang may be fashioned if required for a certain
plant known to abhor a drip from above. The construction then proceeds
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 pleasure
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.

[Illustration: 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]

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 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 of earth. The run should slope downward
slightly.

Rocks calculated to simulate a natural stratification ought to be laid
on an incline 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 planting 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.

[Illustration: Cross-section of rock garden construction, showing
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]

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


There 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 everything until the rocks are in place and the soil thoroughly
settled.

The former plan is a singularly appealing, as well as practical, one.
There is something fascinating in finishing completely 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 established 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 plant, with the earth well shaken from the roots, unless
it has a tap root, laid down horizontally with the crown just outside
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
crevices; this must be all thought out beforehand.

As a matter of fact, the planting plan cannot be too thoroughly thought
out in advance. At point after point it dovetails 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 moisture. The best way is to decide what plants are most
desirable in the circumstances, 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.

[Illustration: Where only a small effect is desired, a tongue of rock
work like this is an easy solution of the problem. Note the avoidance of
straight lines]

The general idea is that all the soil shall be concealed, not
necessarily at the moment 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 single there is a good
planting rule. Colonies, 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
hundred 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 resolve 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
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 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
eternal vigilance, the weak will have the worst of it before you realize
what a mistake 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 exists there will
always be planting. Normal mortality will necessitate some, there will
be thinning out, and time will suggest additions 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 garden, 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 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


So many plants are suitable for a rock garden that the range of choice
is bewildering. In this, as in the laying out of the garden,
advisability takes precedence 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 suitable 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 yourself how things grow, and as for
the hardiness of plants, you have it already tested for you. This refers
not alone to the natural 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 immediate neighborhood are concerned,
their value to the rock garden of the average person with limited time,
who is not obsessed with the idea of growing the rare and curious,
cannot be overestimated. And they are so many; more than most 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-fashioned flowers; there it belongs in that category. But why
should you of Minnesota 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,
gentians 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.

[Illustration: Native plants are excellent material for the rock garden.
The foam flower (_Tiarella cordifolia_) at the top, and one of the
smaller ferns at the bottom]

From ferns alone, or from only plants of shrubby growth, a most
beautiful native rock garden may be made. And adding small flowering
plants, or excluding all else, there are limitless opportunities. It
goes without saying that A's rock garden in Maine will not be like B's
in Louisiana; 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 majus_), strawberry (_Fragaria Virginica_), cranesbill
(_Geranium maculatum_), toadflax (_Linaria vulgaris_), orange hawkweed
(_Hieracium auranticum_), herb Robert (_Geranium Robertianum_),
coltsfoot (_Tussilago Farfara_), Solomon's seal (_Polygonatum
biflorum_), foam flower (_Tiarella cordifolia_), bloodroot (_Sanguinaria
Canadensis_), and some of the violets. These are but a few names, and
random ones at that. Some of them, the coltsfoot, cranesbill, celandine,
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, like certain friends, you enjoy having for a visit, but do not
care to see remain 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 almost as much care, but
in each case there will always be exceptions that are a matter of
individual preference. Few, for example, would have the heart to reject
the dainty little purple toadflax of Switzerland (_Linaria alpina_),
just because it is a biennial. The main dependence, however, must be
placed on perennials--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 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
am[oe]na_, _Aubrietia deltoidea_, maiden pink (_Dianthus deltoides_),
blue bugle (_Ajuga Genevensis_), white bugle (_Ajuga reptans_), woolly
chickweed (_Cerastium tomentosum_), creeping thyme (_Thymus serpyllum_),
dwarf speedwell (_Veronica repens_), _Saponaria ocymoides_, alpine mint
(_Calamintha alpina_), and pink, white, and yellow stonecrops (sedum).
All of them fairly hug the ground. There are other plants that form a
carpet of foliage, but the flower stalks rise higher. These include
white rock cress (_Arabis albida_), the permissible double buttercup
(_Ranunculus acris fl. pl._), the also permissible double German
catchfly (_Lychnis viscaria_), another double flower, "fair maids of
France" (_Ranunculus aconitifolius_), Carpathian bellflower (_Campanula
Carpatica_), grass pink (_Dianthus plumarius_), _Iris pumila_, crested
iris (_Iris cristata_), Christmas rose (_Helleborus niger_), _Phlox
divaricata_, _Phlox ovata_, _Phlox repens_, foam flower (_Tiarella
cordifolia_), _Veronica incana_, _Alyssum saxatile_, _Saxifraga
cordifolia_, and various avens (geum).

Several of the primulas give a like effect if the planting is close--as
it should be in a pocket. The best are the English primrose (_Primula
vulgaris_), cowslip (_P. veris_), oxlip (_P. elatior_), bird's eye (_P.
farinosa_), yellow auricula (_P. auricula_), _P. denticulata_, and _P.
Cortusoides_. 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 cottage types
may be used, if in a solid color, but most to be preferred are the
species, such as the sweet yellow (Florentine) tulip of Southern Europe
and the little lady tulip (_Tulipa Clusiana_). Crocuses are also best in
type forms, and the small, single, 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 Sibirica_, glory-of-the-snow
(_Chionodoxa Luciliæ_), guinea-hen flower (_Fritillaria Meleagris_),
grape hyacinth (_Muscari botryoides_), _Triteleia uniflora_, _Allium
Moly_, and the wood and Spanish hyacinths (_Scilla nutans_ and
_campanulata_).

Taller plants that may be worked in, oftentimes best with only a single
specimen or small clump, are autumn aconite (_Aconitum autumnale_),
_Yucca filamentosa_, leopard's bane (doronicum), single peonies (either
herbaceous or tree), German, Japanese, and Siberian iris, as well as the
yellow flag (_Iris pseudacorus_), single columbines, _Anemone Japonica_,
_Hemerocallis flava_, _Sedum spectabile_, _Dielytra spectabile_,
_Dielytra formosa_, Jacob's ladder (_Polemonium Richardsonii_),
fraxinella, _Anthemis tinctoria_, single _Campanula persicifolia_,
_Campanula rapunculoides_, _Campanula glomerata_, globe flower
(trollius), snapdragon (antirrhinum), platycodon, lavender (where it is
proven hardy), and musk mallow (_Malva moschata_).

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.

[Illustration: A rock garden merging into woodland. A curved path is
desirable, as it affords a greater number of vistas]

The pick of the low shrubs are the charming _Daphne cneorum_, which
flourishes better for being lifted above the ordinary garden level, and
_Azalea am[oe]na_. 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, 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. Wichuraiana_, 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 moisture 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 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 _Gentiana 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 small stone wedges. The best kind is a five-foot
retaining wall, as there is then 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.

[Illustration: Planting plan of dry wall, the dark portions representing
the chief earth-filled crevices. The plants are: 1--_Arabis albida_;
2--_Alyssum saxatile_; 3--House leek (sempervivum); 4--_Viola tricolor_;
5--_Armeria maritima_]

[Illustration: A wall garden planted in colonies--the better way. If not
too vigorous of growth, vines may be planted as shown here at the base]

Although the face of the wall in either case may be strictly
perpendicular, it is better that each layer should recede a bit.
Construct it after the manner of the rock garden, laying the stones so
that the top will be level, or approximately so.

[Illustration: Dry wall for retaining bank. Cross-section, showing
crevices, soil runs and tilting of rocks]

In planting also, follow the same rules. It is better to plant as the
work progresses. 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.

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

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_, red valerian (_Centranthus ruber_),
aubrietia, _Alyssum saxatile_, snapdragon, wallflower (_Cheiranthus
Cheiri_), Kenilworth ivy, _Viola tricolor_, _Dianthus plumarius_, and
_Dianthus deltoides_ are all very serviceable. 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 foliage 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 occasional small
stone should be removed.

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




WATER AND BOG GARDENS


Neither the water nor the bog garden 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 picturesqueness. If water is lacking, it may
often be introduced at little expense.

[Illustration: A little grotto with trickling water makes a picturesque
break in a wall garden. If shady, plant ferns generously]

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
below what will be the level of the water, and then setting rough stones
on that. A cement bottom for shallow water may be disguised by
imbedding pebbles and small stones in the cement before it sets.

[Illustration: 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]

Dispose the rocks very irregularly, but they may be so few as to be mere
notes. Avoid stagnant water, and if mosquitoes are feared introduce some
goldfish. They like mosquito larvæ.

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.
Forget-me-not is one of the finest plants for the banks. Use the
perennial kind (_Myosotis palustris 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.

       *       *       *       *       *

[Transcriber's Note: Two oe ligatures in the original book have been
rendered as [oe]. A spelling error in the original has also been
corrected: "Polemonicum" to "Polemonium" (Page 41: "... Jacob's ladder
(_Polemonium Richardsonii_) ...") Italics are rendered as _underscores_.]





End of Project Gutenberg's Making A Rock Garden, by Henry Sherman Adams