Ornamental trees, such as flowering dogwoods, crab apples, and Canadian redbuds, are deciduous plants that are used particularly for their appeal of seasonal change. Plant materials are another element used in the spatial composition. Plant materials can function in a variety of ways on the residential site. These functional uses can be: (1) architectural, (2) aesthetic, or (3) engineering. The permanence of coniferous evergreens should be used in direct association with deciduous plants so that a composition of plant materials retains some structure and green color during the times of the year when deciduous plants are without leaves. On the residential site, plant materials are one of the most important design elements for the floor, walls, and ceiling of outdoor rooms. Although plant materials can be categorized in numerous ways, one such way is by “type.” They are (1) deciduous plants, (2) coniferous evergreen plants, and (3) broad-leaved evergreen plants. Coniferous evergreen plants are those that have needlelike foliage. Broad-leaved evergreens have leaves that resemble deciduous foliage in appearance. Deciduous plant materials lose their leaves in the autumn and regain them in the spring. During preliminary design, the designer takes a “broad brush” approach to the use of plant materials by deciding where plant materials should be located and what function they serve in the design. Because coniferous plants retain their foliage throughout the year, they can be used wherever a permanent mass of foliage is required. Coniferous evergreens are particularly useful for screening undesirable views or blocking cold winter winds. Because of this quality, they are often used to emphasize seasonal change and variation. Specific selection and identification of plants by genus and species are usually done when the master plan is prepared. Broad-leaved evergreens can also be used to give a dark yet shiny leaf surface to a planting composition. They are living elements and need special care in selection and placement in the landscape. Each of these types is briefly described in the following paragraphs. However, they should not be used only for their flowers because these last only a few weeks of the year.