Rock Garden Construction
The actual construction of the rock
garden demands a lot of thought and care.
The wildness of
plants, their freedom of growth, and the natural way in which they spring from the rock fissures, unfits
them for association with plants of calmer habit.
The proximity of
well graveled paths, of mown turf and trim borders, robs the rock garden of all its significance and charm,
making it appear but an untidy heap of stones overgrown with straggling vegetation. Isolation, then, should be
the first thought when planning an ideal home for rock plants and Alpines.
The worst positions
would be found near walls, buildings and fences, which are as far as possible removed from the wild spirit of
the mountain solitudes. Trees should not be found near the rock
garden, not merely for aesthetic considerations, but because their roots, far reaching and greedy, will
impoverish the soil.
Alpines, and indeed
most rock plants, demand the fullest exposure to sun and air. The damp, still atmosphere which prevails in tree
sheltered spots, is not conducive to their welfare.
When a pathway is
cut through a high bank, as is often necessary in hill gardens, the steep sides may be prepared for planting by
the use of stones to form rough walling.
succeed better on these almost perpendicular faces than on level ground, and the walls are so constructed that
they show no trace of mason's work, but resemble rather the sheer drop of a miniature cliff. Raised banks
between two sections of the garden, natural knolls and wild craggy ground covered with furze and heather,
suggest themselves as other spots offering inducements for conversion into rock
Where natural rock
stratum exists a few inches below the soil, it will always be better to make the rock garden by excavation
rather than by the addition of fresh stone work. In such cases the practice of employing artificial stone
substitutes, when there is already a natural outcropping of rock in the ground is bound to be strongly
If natural stone is
unobtainable use the artificial substitute.
When starting the
actual work of rock
garden construction, one thought must be kept prominently in view - the requirements of plant life take
precedence over considerations of the picturesque.
For this reason, it
is the gardener, not the builder, who should arrange the disposition of the rocks. The rock garden is a home for
plants, and the beauty afforded by the stones themselves, though not inconsiderable, is quite
Elevation in rock
gardens should always be obtained by masses of earth, and not by stones piled one above the other, with soil in
the crevices. The foundation of large banks may consist of brick ends, builders' rubbish, and any convenient
material, but above this should be soil to the depth of at least two feet.
Too often we see
flat rocks laid so as to form a series of ledges, or pinnacles in which each stone is carefully balanced on its
predecessor. Handfuls of soil are crammed into any convenient crevice, and in such unpromising quarters plants
are expected to grow. Naturally, as soon as the roots have pushed their way through the ball of soil, they are
in a barren airchamber, and during a dry summer half of them perish.
In the well built
rock garden the soil is rammed firmly home, and no vacuum exists between adjacent stones. Rocks which are
hollowed out on the under side must be sunk into loose soil, so that the cavity is completely filled. Unless the
work is made firm in all its stages, the effect of frost and heavy rain will be to cause soil subsidence,
leaving innumerable air spaces.
At this stage it is
helpful to study rocks in their natural positions. An area of English moorland offers a striking object lesson
in this respect. On level ground, smooth rocks, usually of fair size and round in shape, rise a few inches above
the ling and heather. Occasionally we come upon a slight knoll or ridge, from which a cluster of lichen
stained rocks thrust themselves boldly. The higher the ground, the more rocks, and vice versa. The fact is one
which should be remembered in garden making of this description.
Always use the
smooth flat stones for the lower levels, and be content with quite a few. Higher up the bank the plants will be
smaller and the boulders more conspicuous, whilst at the top tufts of diminutive Saxifraga
and Androsace will cling to the sides of the roughest and most weathered rocks. This is not an attempt to
imitate Nature's methods, but it is adopted because in no other way do the various families of Alpine plants
appear to so great advantage.
Stones should be laid in the
earth with their broadest sides downwards, the bases should also be sunk in the soil. Lines of natural
stratification should be simulated where possible, as this produces a more restful and coherent
If the stones are
of small size, and the rock
garden slopes abruptly, it will be necessary to build an occasional course of dry-walling, otherwise the
earth will slip forward after heavy rain. The walling must be built very carefully, as it is important that all
trace of builder's work shall be concealed.
largest stones available, a single course should be laid somewhere about the ground level. The earth must be
well rammed, and the spaces between adjacent stones filled with soil.
A thick layer of
soil is now placed above the stones, in the same way that mortar is spread between lines of bricks. A second
course of stones is now put into position, no idea of uniformity in size being entertained. The dry-walling is
carried up as far as necessary. In the case of almost perpendicular slopes, it will be convenient to make a
series of ledges, as these permit freer planting, and serve to break the monotony.
When setting the stones, it is desirable that each should be placed so that it
tilts slightly backwards, in other words, the front faces are not perpendicular. Not only does this serve to
strengthen the wall, but the rain collecting in tiny runnels, soaks into the earth crevices and refreshes the
plants. This rule holds good as regards the disposition of all stones and rocks in the Alpine
These sections of
dry-walling, which are necessary in nearly all rock gardens formed on banks, require to be closely planted. The
joints and seams between the stones should be completely hidden by Saxifrages, Ferns, Alpine Primulas and
Then if the stones
have been laid so that they simulate the lines of natural strata, the idea of a wall will give place to a solid,
unbroken rock face, in the fissures of which various small plants have established
When building, it
is convenient to lay a wooden spline vertically against the front face of the rock wall from time to time. It
will then be easy to ascertain if the centre stones are in a line with the rest, or are too much advanced. The
latter is a serious error in rock building, as sooner or later it leads to the bursting outward of the whole
structure and the loss of many valuable plants.
considerations of economy, local stone should always be used, as being most likely to harmonise with the
character of the surrounding vegetation. Sandstone blocks are extremely useful, this material having the
additional advantage of weathering to a picturesque shade.
Limestone is also
good, but slaty, crumbling material is of little value, as it soon succumbs to the disintegrating influence of
the atmosphere. On no account should gnarled tree roots, broken stumps or woodwork of any description be
included in the rock garden.
The paths in the
rock garden should be of the simplest description. They need never be of greater width than two persons walking
side by side, whilst the smaller back paths should be capable of admitting one. A good effect will be obtained
by sinking irregular stone slabs at intervals, much in the way that the native rock appears along the foot-worn
track on mountain side or cliff path.
Flat stones by the
path edge, with an occasional rock jutting out from the garden slopes, will help to disperse any appearance of
formality. Coarse gray gravel and small stones will form the best surface, and provide a dry, clean footway in
There are many
small plants which establish themselves readily among the edging stones and at the sides of the slabs in the
pathway itself. Such are the Woodsias, Asplenium and other Alpine
ferns, the creeping Sandwort (Arenaria) and the little violet flowered Wall Erinus
Herein lies the
beauty of the rock garden, for even as we walk there are flowers crowding the pathway, space is never wasted,
there is always some tiny plant willing to occupy the smallest crevice.
connecting the different levels add much to the picturesque appearance of larger rock gardens. They should be
quite informal, and if carefully made will look as though they had been roughly hewn out of the living
A long narrow stone
slab should be fitted to the front edge of each step, or if this cannot be managed, two or even three smaller
pieces connected by sunken cement joints. The cement will afterwards be concealed by small plants and mosses,
which may be naturalised by the scattering of a few seeds in a pinch of soil.
It is not necessary
to pave the tread of the steps, but a few pieces of flat stone may be inserted here and there. For the rest,
they may be made firm and level with earth and coarse gravel.
In a short time the
plants bordering the steps will throw out creeping stolons, draping the sides, dwarf Campanulas
will thrive in the joints, and in the corners, safe from the foot of the careless, Rockfoils and Stonecrops will
thrust forth their tiny blossoms.