It may be worth while to explain to the novice in rock gardening that a soil “ pocket “ so frequently referred to is a flat bed of soil, supported by rocks. The rocks are tilted slightly into the bank of the rockery, so that rains falling on them are carried into the soil, tothe plant . Soil is then filled in wherever it will remain, and forms a series of flat-surfaced pockets, or ledges, down the banks of the rock garden.
Many a beginner has tried the method of making first a bank of soft soil, and then pushing in rocks here and there—with disastrous results. The first heavy rains wash the soil down, and probably unsettle the rocks. In any case the rock garden so made looks “like a decorated trifle, with almonds over it,” as one writer has aptly said, instead of looking like a piece of natural scenery.
Arrangement of the plants in a rock garden is a matter of artistic ‘impression. A good plan when water is included in the picture is to begin with the water feature, attempt must be made to alternate colours along a stream-side Rather should groups be collected—several patches of musk in one part of the stream, and several patches of forget-me-nots in another, and so on.drifts of colour or foliage along the waterside. It will seem more natural if these drifts are irregular in form and size, and certainly no
Bold colour masses in the dry parts of the rock garden can be arranged as desired, but with some effort to dispose these so that the various seasons are represented in all parts of the picture.
Dwarf shrubs, particularly those of characteristic form, such as pyramid conifers or columnar conifers, or broad spreading shrubs
that drape gracefully over rocks, will be used by the artist where they are most effective. This is often somewhere near the eye-level; very rarely are such shrubs satisfactory on the horizon of the picture. The highest point of a small rock garden can very often be best used as a site for a garden seat, this serving much the same purpose as the “ mount “ which is made to overlook Tudor gardens.
The mention of shrubs brings to mind the wide variety in rock garden plants. There are, in fact, all the kinds of plants used in the ordinary landscape or garden—shrubs, bulbs, grasses, carpets, herbaceous perennials,, —available for the rock gardener, and the majority of plant families are also represented among the smaller plants suitable for rock gardening.
In most cases, the use of the various plants on the rockery slopes is similar to their use in the main garden. The carpet plants are allowed to spread their colours over the soil as they will, except where they outgrow their allotted. Herbaceous perennials are lifted and divided occasionally, as in the herbaceous border. Annuals are sown under glass and pricked out, or sown where they are to bloom. Biennials are treated as are biennials for the spring and summer flower beds, though these too can, if desired, be sown where they are to flower.
Bulbs and shrubs are both used in rather a different manner in the rock garden from that employed with them in the larger garden. Bulbs are chosen from among the available miniature types—dwarf daffodils, scillas, snowdrops, chionodoxas, tulip species of a daintier type than the florists’ tulips, dwarf iris, etc. They are not replanted every year, but form a part of the permanent planting scheme of the rock garden.
One of the best ways to use bulbs in the rock garden is to set them in the same pockets as some of the carpet-forming plants, so that the bulb foliage and flower spike come up through the green carpet and flower early, while the carpeter carries itslater in the same pocket. with arenaria balearica, scillas with globularia nana, and the dwarf types of narcissus with mossy saxifrages all result in two seasons of flower from the same pocket.
Shrubs are differently used in the rock garden for the chief reason t hat masses of shrubbery are never desirable in this planting scheme. Shrubs used should be either outstanding specimens, or low-growing drapery shrubs designed to soften the hard outline of the rocks.
That is the reason why rock shrubs must be very carefully placed, for the least suggestion of” shrubbery” will quickly become obtrusive in the picture. This does not mean that shrubs must be always isolated specimens. In a large rock garden a bank of shrubs, growing from almost vertical crevices in huge quarried rocks, is a
delightful background; but shrubs in a rock garden should never be allowed to obscure a view.