In horticulture the landscape-architect is concerned with a study of the plant as an individual, its growth, propagation, the formation of new varieties, pruning, spraying, and the best methods of planting and handling.

Horticulture may be divided into two classes, the economic and the decorative. The decorative aspect is of chief importance to the landscape-designer, as the economic side appears only in such problems as the disposition of orchards and the screening of objectionable features. This last consideration is nevertheless of as much importance as the first, and is as much a question of esthetics as of economics.

The ornamental side of horticulture deals with all the plant materials used in landscape-gardening. The horticulturist groups these according to methods of growth, and classifies them according to size and soil requirements; but the landscape-architect primarily considers them with regard to form and color. Horticulture gives the landscape-architect the majority of the materials with which he has to work, for he is generally called in where planting is to predominate, and he must accordingly be thoroughly familiar with it.