Rock Garden Construction

The actual construction of the rock garden demands a lot of thought and care.

The wildness of Alpine 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.

Many Alpines 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 gardens.

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 marked.

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 secondary.

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 Saxifrage 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.

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