MINIATURE WALL GARDENS
Any small section of low wall—brick, cement, stone, or concrete—can be the background for a miniature garden. But it is in a dry wall, built of stones without cement, that many small rockery plants best display their jewel-like perfection. Planted horizontally, with their roots in pockets between the rocks, they make a vertical rock garden of glowing colors and fascinating foliage textures.
For small, low walls, and those in somewhat formal settings, thin-layered rock such as slate or shale is usually preferred. Irregularly shaped fieldstone or other rocks of native origin are used in more natural, informal designs. Any lines of stratification are, of course, laid horizontal and parallel to each other. Another good rule to go by is: The smaller the wall, the smaller the rocks.
Construction
Low walls (two feet high or less) usually do not need a foundation layer sunk below the frost line. They can be started at, or just under, ground level. But they must be set solidly on a firm, wide base—two feet wide, for example, for a wall two and a half feet high. Set the largest stones and complete the lower layer first. Tilt each rock slightly backward and downward so soil won’t wash out of pockets, water will run back to plant roots, and the heaving pressure of frost won’t thrust the rocks out of place in winter. A guide line of string or wire moved up with each new layer will help you keep the construction level.
The wall should slant slightly in toward the bank behind it, and usually grows more narrow as it goes up. Each layer is made absolutely solid before the next is applied. Set each stone so that it is completely steady, and rests on parts of two stones beneath it. This distributes weight evenly, avoids crushing plant roots, and prevents unattractive and impractical long, vertical cracks created when joints coincide. Use small, flattish rocks to fill chinks under large stones and make them steady.
Behind the wall, as you build, firm in a goodly layer (one foot thick is usually recommended) of topsoil that has been enriched and aerated to promote drainage. Roots will reach back here for water and food. As you ram soil into pockets, make sure it reaches all the way back to this layer. Unless all the soil is made very firm, it may settle and the stones may slide out or into the bank.
At the top you can leave some pockets for plants, or plant them just behind the wall. Cover cracks at the top with flat stones, so water won’t wash out soil.
A rock, a rose, and a miniature rose.
Planting
If you can remember not to damage plants at the bottom as you’re working above them, set the plants in each layer as you build. It’s easier then to make sure the roots are firmly embedded well back into the soil. Plant sparsely; leave plenty of room for growth and spread, and plenty of uncovered wall surface to contribute pattern and texture to the picture. Space the plants at irregular intervals, never in straight lines either horizontal or vertical. Water thoroughly, making sure the layer of soil behind the wall is completely moist; and keep it moist at least throughout the first growing season.