The Golden State: Where & How to Live, Secure, Visit, Enjoy and Thrive in California
Art Of Landscape Architecture
"In such a wall wild plants will already have made themselves at home, and we may only have to put a little earth and a small plant into some cavity, or earth and seed into a narrow open joint, to be sure of a good reward. Often grasses and weeds rooting in the hollow places can be raked out and their spaces refilled with better things. When wild things grow in walls they always dispose themselves in good groups; such groups as without their guidance it would have been difficult to devise intentionally."
These walls, ancient or recently made, are valuable in many places, bordering roads and lanes, supporting steep banks, and making the main structures of bridges and their approaches; but it should be understood that, in order to have a rustic character, they should be made of stone collected in the fields near where they are to be used, or taken from a quarry where the rock shows a cleavage or lamination, a colour and grain which suit the character of the region where it is to be employed. Next in importance to the character of the stone is the size of the individual blocks used. These should be taken as large as possible and should not show any signs of the chisel, only a blow of the hammer here and there, to break off corners so that a rough fitting can be made. To this end, no chinking or thrusting little pieces of stone into the joints should be allowed. All these crevices or openings should be left exposed and then, by devising lips or pockets of cement, soil can be introduced and retained for growing plants. This will in a year or two, when the plants have grown, give an old weather-worn appearance to the wall, an ancient moss-grown look, and at the same time a great charm of leaf and flower. Any concrete that may be necessary should be set in the core of the wall where it is out of sight. There are few rock plants that will grow in America, or even elsewhere, in these dry crevices, and such plants are confined largely to the mossy-looking sedums of dwarf habit, preferably the stonecrop (Sedum acre). Besides these there are the wild cactus or prickly pear (Opuntia vulgaris), the houseleeks (sempervivums), which do well in these difficult places. Hardly any other kinds can be used for the purpose.
At the base of these walls ferns, iris, saxifrage, and other medium-sized herbaceous plants that bloom at different parts of the season may be grown, but the kinds should be selected so that only the base of the wall for a foot or two is covered, because the beauty of the grain and colouring of the wall is quite as important as the plant growth.
