While "Rock Gardens" is the modern name, another term used in connection with natural rock gardening is "rockeries". The biggest problem is to determine the plants that are likely to succeed under the conditions that can be provided. There are no plants that can be counted as rock plants in every part of the country; therefore, plants must be selected for the particular locality where they are to be grown. The background or setting for the rock garden varies greatly because of the topography and character of the country. In a rough, rocky country rock garden sites are sometimes found almost readymade, but in other sections they must be created from materials collected for the purpose. In the latter case care is necessary in order to produce a result that does not look forced or out of place. When building a house on a rocky hillside it may often be possible to reserve an adjacent area that may be made into a most attractive garden with but little modification. Even old quarries can be and are converted into attractive gardens. Where, however, such features have to be built, it takes a good student of nature to reproduce naturalistic rock ledges and other stone outcroppings. Boulders (rounded, waterworn stones) may be scattered over a gentle slope, whereas on a steeper slope the stones must be placed close together, at some points even resting on one another. Even rock walls may be part of a rock garden.
Rock Walls Quarried or angular field stones often may be appropriately used to hold artificial banks. Stones with weathered faces are usually more attractive than those with newly cut or broken faces. Where there is a gentle slope, a row of stones may be placed at the bottom, with spaces between them two or three times as wide as the stones; other stones may be placed behind these spaces with the bottom as high as the tops of the front stones and back far enough to hold the soil at the desired slope. Where the bank is steep the space between the stones, often only 2" or 3", may be filled with soil and the next stone laid over this opening, resting on both the lower stones and set as far back as the desired slope of the wall will permit. Stones should not be uniform in size, and those more irregular in outline than is desired for building purposes make a more attractive wall. If the stone has a relatively flat upper surface, the surface should be so placed that water falling on it will drain back into the wall and not off.
Elizabeth Passage