Plant materials are another element used in the spatial composition. On the residential site, plant materials are one of the most important design elements for the floor, walls, and ceiling of outdoor rooms. They are living elements and need special care in selection and placement in the landscape. They can be used by themselves or in conjunction with other elements to create outdoor rooms and reinforce the design theme.
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. Their selection must be based on function, appearance (size, form, foliage color, flower color, foliage texture, fruit size, and color), and environmental conditions present on the site (sun exposure, wind exposure, precipitation, soil characteristics).
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. Each of these types is briefly described in the following paragraphs.
Deciduous plant materials lose their leaves in the autumn and regain them in the spring. Because of this quality, they are often used to emphasize seasonal change and variation. In addition, many deciduous plants are distinguished by showy spring flowers and dramatic autumn foliage color. Ornamental trees, such as flowering dogwoods, crab apples, and Canadian redbuds, are deciduous plants that are used particularly for their appeal of seasonal change. Deciduous trees can be used for shade during the hot months of the summer while allowing exposure to the sun during the cool months of the winter.
Coniferous evergreen plants are those that have needlelike foliage. Because coniferous plants retain their foliage throughout the year, they can be used wherever a permanent mass of foliage is required. 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. Coniferous evergreens are particularly useful for screening undesirable views or blocking cold winter winds. In addition, they can be grouped together in a mass to create a backdrop for showy deciduous plants.
Broad-leaved evergreens have leaves that resemble deciduous foliage in appearance. However, broad-leaved evergreens retain their leaves throughout the year. Broad-leaved evergreens as a group are best used in a design for their foliage texture and for their showy spring flowers. However, they should not be used only for their flowers because these last only a few weeks of the year. Broad-leaved evergreens can also be used to give a dark yet shiny leaf surface to a planting composition.
Specific selection and identification of plants by genus and species are usually done when the master plan is prepared.
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.