LOCATION AND DESIGN:
An informal design is most effective, and simplicity is very important. Unless the area is quite large, avoid the use of excessive numbers of plants or elaborate rock formations. The most desirable location is a steep bank that may be available at the back or side of the property.
A pool of water or a miniature stream and waterfall will add charm to the rock garden. Trees are desirable to provide partial shade, and shrubs should be used for background. If adequate space is available, the garden may include paths made with flat stones or pine needles and steps on steep slopes to encourage closer inspection and greater enjoyment.
Plan the rock garden for easy maintenance. The most attractive ones are usually so wide you cannot reach to the center to remove undesirable weeds, prune plants, or set out new species. A sufficient number of large flat or rounded stones should be present to serve as a place to walk or stand while doing maintenance jobs in the garden. These must be deeply imbedded to provide secure footing as you work.
A rock garden should express the creative ability of the gardener to use the terrain and plant materials that are available. Each garden should be a unique development and not a reproduction of one that has been observed on other residential or public property.
CONSTRUCTION AND SOIL:
The construction of a rock garden is easy if an irregular terrain is available. A rocky hillside or a series of ledges with small irregular terraces for plants works well. For the best effect, at least half of the surface should be made up of exposed rocks.
If more rocks are needed, use weathered native stones. Start at the base of the slope, and work up from there. Place the rocks in a natural position with strata in the same plane as existing material. Tip the stones toward the bank to cause water to run into the soil around the roots of your plants. The rocks should be large, and each one should be about half buried in the soil to make it stationary.
Provide an adequate depth of good soil for your plants in the pockets between and behind rocks. This should be done while the garden is being constructed. The soil should be well drained to a depth of at least 18 inches to promote desirable growth of plants. Most rock garden plants cannot tolerate poor drainage.
Add compost or shredded peat moss to the soil to increase the organic matter content, and add dried manure to improve the fertility. Do not use too much manure -- it will cause excessive vegetative growth of your plants. A mixture containing 2 parts loam soil, 1 part shredded peat moss, and 1/2 part dried manure is suggested.
PLANTS FOR THE ROCK GARDEN:
Except for trees which provide partial shade and shrubs which serve as background or accent features, most of the plants in a rock garden should be relatively small or dwarf in size. Plants are used to complement the rocks and must not hide or detract from the beauty of the stones.
Plants for the rock garden should require a minimum of care. Select plants that will tolerate the growing conditions, such as a wet or dry soil or an exposure that is windy, hot and sunny, or cool and shady.
Dwarf evergreen shrubs may be used to give a permanent quality to the rock garden. Hardy native ferns, perennial flowering plants, miniature roses, and spring-flowering bulbs add interest and color. Except for a few carefully selected accent plants or groups, the flowers should be somewhat inconspicuous and similar to the wild areas the rock garden is intended to emulate. Avoid the use of large masses of plants or those with oversized, intensely colored blooms. Annual flowers should be used sparingly, especially such common species as petunias, or the large-flower varieties of aster, marigold, or zinnia.
Consult the catalogs of nurseries and seedsmen who offer dwarf shrubs, native plants, perennials, and bulbs. In some catalogs, plants suitable for rock gardens will be listed in a separate section. The pictures and descriptions will help you select plants suitable for your particular garden.