The Method of Treatment. The lists of plants do not represent a complete and thoroughly exhaustive study of the subject. The general discussions and groupings will provide persons interested in the use of plant materials with essential facts, in a compact form, concerning the appropriate use of the more permanent species of trees, shrubs, vines, perennials, annuals, and bulbs.

The study of plants and their specific uses in landscape planting, can to some extent be analyzed and tabulated for reference purposes in the same way that plants are grouped for purposes of identification. This study, however, is not based entirely upon scientific facts, and therefore is subject to personal points of view, and many times no hard and fast line can be drawn which will place any one plant in one list in preference to the possibility of placing it in some other list.