How to Build a Rock Garden
The rock garden is essentially an informal feature, an attempt to reproduce the natural setting of alpine plants, and should not be sited too near formal flower beds. The design of a large rock garden calls for expert knowledge and is best entrusted to a specialist contractor, but a modest rockery in a small garden can be built successfully by amateur if he pays attention to its design, materials and construction.
Often there is a little choice in matter of site, and it is true that a rockery may succeed in almost any location and aspect, but most rock plants need the fullest possible sunshine. At all costs avoid siting the rockery under large trees or where there are draughts. Drainage must be carefully considered, since the alpines are liable to die in a waterlogged soil. On heavy clay soil it is worth while stripping off the topsoil first and using a layer of clinker or other porous material as the foundation. This is covered with subsoil mixed similar material and built up roughly to shape; then the topsoil is used for the surface. A useful tip is to plan the rockery around the key feature, such as a stone outcrop as a slope, as illustrated stage by stage here.
material, one cannot do better than use of natural rocks, preferably of local
stone and some examples are shown. They include Delabole slate from Cornwall
and sandstone from Sussex. Whether worn Westmoreland stone is seen at an early
stage of construction of rockery in woodland setting, and the same material
worn by water in a pretty cascade. Rustic slate is also a good option to use in the rock garden.
Cotswold Stones make a classy statement in any plot. These shingles are ideal to construct gardens featuring rocks or making dry stone walls. In addition, these stones look extraordinary as feature stones dotted around to add visual interest. Cotswold Stones are not fish friendly since these have limestone content.
White Cobbles look really spectacular and will aid in giving an amazing view in any plot. It successfully gives a contrast to other dark rocks and gives a pleasing effect. It is to be noted that these are not fish friendly because of limestone content.
Grey Sparkly Stones are remarkable with their soft gray shades and have those twinkling sparkles when sunshine falls on the flecks of these rocks. These produce clever and elusive effect to any rock garden or water feature. These can be used to construct a hardy rocker garden or, use them in a water feature, or use a small number of these rocks to put in impact and elevation in planted beds.
Blocks of Cheshire Red Sandstone blocks are idyllic for a beginner to make a rock garden specially for small sandstone artist projects. This stone has been used for numerous buildings throughout England.
The building and planting of a rock garden depends very much on individual requirements, but the example given here shows the general principle.
A natural effect has been obtained by constructing outcrops of stone in an irregular mound and planting alpines between the boulders. The rocks are tilted so that rain is diverted to the plant roots, and at least half of each is embedded in the ground. (Each rock should be tested to ensure that it will bear one’s weight when being laid.)
Only large rocks have been used in the construction, as small pieces do little to help the effect. The topsoil used is mixed with about half of its volume of leaf-mould or peat and with plenty of coarse sand.
For an example, we can create a rock garden which contains easy to grow rock plants that will succeed in most such situations.
Iberis or annual candy turft is a good choice for a pocket of soil. Polygonum affine, 9 in. high, hangs over stones and produces spikes of rosy flowers. Campanula garganica, only 3 in. high, has blue star flowers from June to August. Aubretia is excellent for ground cover, its carpet for red, pink or purple flowers making a bright splash of color in spring. Rooted in a moist pocket, it will rapidly spread.
Cistus, sometimes called the sun rose or rock rose, is an evergreen shrub up to 2 ft. high; the large white flower has a crimson blotch at the base of each petal. Dianthus caesius, one of the rock garden pinks, is another good spreader and needs nothing more than well drained soil and plenty of sun. Saxifrage and veronica also appear in the rock garden. Both have many dwarf species which need a little attention once established.
Stonecrops will root anywhere without difficulty and require very little water once they are established; the evergreen. Sedum spathulifolium forms a clump and has galucous rosettes that produce 6 in. stems of yellow flowers; blooms June to August.
- Arabis albida or rock cress is a fine double white trailing plant with grey foliage;
- it is increased by cuttings and tends to spread rapidly;
- a single flowered form has variegated leaves.
Shortia uniflora is an alphine for leafy, limefree soils in almost complete shade; it has pale pink and white flowers in spring and grows about 6 in. high.
Edelweiss is a hardy, silvery-haired perennial (Leontopodioum alpinium) that thrives on an exposed sunny rockery; needs sandy soil; flowers in June and July.
Geraniums or cranesbills are vigorous little plants with attractive foliage and blue, purple, pink or crimson flowers in early summer; there are several species, the one illustrated being the dwarf Geranium napuligerum.
- Gazania should be treated as half hardy and wintered under glass;
- its orange blooms (July-August) are showy;
- its often seen growing on dry walls and it thrives in chalky soil.
Soldanella or moonwort is a dainty little alpine, up to 6 in. high, with blue or violet flowers in April; its foliage forms a creeping green mat; likes a well drained sandy soil.
Rock Violas make bright splashes of color through the early summer; some prefer a shady nook and other thrive in the sun;
Viola lutea is one of the easiest to grow, producing masses of delicate yellow or violet flowers.
An unusual gentian both for color and size is Gentiana lutea. It has deeply ribbed foliage and tall spikes of citron yellow flowers in late July. As it grows up to 6 ft. high, plant it in an out of way corner.
Anemone Pulsatilla is but one of the many delightful wind flowers suitable for the rock garden; the silky mauve flowers appear in March on hairy stems 6 in. high; it flourishes in semishade and prefers chalky soils.
Saxifrages consists of some 300 species, grouped into sections and mostly suitable for the rock garden or alpine house. The kabschia section forms compact cushions of silvery green leaves. It needs soil containing gritty loam and leaf mould, with limestone chips and shelter from very hot sun. Saxifraga burseriana, with enormous white flowers on red stems (February - March), is a Kabschia and one of the finest of all saxifrages. Another, very easy to grow, is Saxifraga apiculata, withprimrose-yellow flowers on 3 in. stems (March-April). The Porphyrion section creeping and mat forming, contains Saxifraga oppoitifolia which has prostrate foliage and carmine flowers (March - April). It prefers a gritty porous soil in a cool moist position, and will also grow on limestone.
Rock garden pockets
It is possible to grow many different kinds of plants in the pockets between rocks, since these can be filled with various kinds of soil to suit. Bulbs are always a good choice as they will provide color on the rockery from the end of winter onwards.
Here, the bold group of chrysanthus has been left undisturbed in its pocket to form a colony. Many good varieties of this early flowering crocus are available.
Heavenly blue muscari or grape hyacinth makes a brave show in a pocket, its bright sky blue flowers contrasting with grey stone behind (April).
This is another plant which, if left alone will soon make a large group.
The primula family is particularly useful in the rock garden. The many species vary in height from a few inches to 4 ft. and nearly every color is found. Most thrive in leafy pockets in sun or semi shade.