T. Davis Sydnor
Considering the functional use of plants is a new approach to solving landscape problems. Traditionally, plants have been used for beautification due to their aesthetic qualities. The expression "functional use of plants" helps to explain that plants can perform other functions in the landscape and still beautify.
Plants have horticultural characteristics such as height and spread, branching habit, flowers, fruit, and foliage; they have design qualities such as form, color, texture, and mass; and they have cultural requirements for growth in the landscape. More recently, the functional characteristics of plants have been recognized.
Figure 1. Groups of plants may be used architecturally to form walls, canopies or floors.
Plants can be used functionally to solve some of the environmental problems the homeowner may have on the property. This may include the need for privacy, protection from glare or direct sunlight into windows, or shade on a patio. A thick row of high shrubs bordering a road can reduce noise and prevent litter from entering a yard, or perhaps screen an unpleasant view such as a shopping center or row of buildings.
The contemporary approach to planning a residential landscape incorporates a design process. In the process, the needs and goals of the owner and conditions of the building site are identified. An analysis of these goals and conditions reveals needs and suggests a program for enhancement of the landscape. It must be realized that not all landscape problems can be solved with plant materials alone; pavements and structures are equally important. Fences and walls are as functional and provide as much privacy as woody plants--and they may require less maintenance.
Figure 2. Plants can be used to screen the hot summer sun while allowing sunlight through bare branches in winter for a type of climate control.
Plants can be used to form walls, canopies, or floors by taking advantage of their different growth habits and foliage characteristics. A stand of trees or shrubs can create walls to filter or block views, or a canopy of tree branches can provide a sense of shelter. Ground cover planting with uniform foliage and textural characteristics can present the feeling of an architectural floor. Plants can also define a boundary (Fig. 1).
Trees can stop or diffuse light before it reaches the ground. Engineering functions of plants include using them to screen or soften the sun's glare on the water or smooth shiny surfaces (Fig. 2), or to block car lights or street lights (Fig. 3).
An edging of ground cover plants along an entranceway or at corners of a walk helps direct attention and movement of people. Traffic movement along walks and drives can be controlled with shrubs or trees (Fig. 4).
Figure 3. This engineering with plant design reduces light glare.
Plants can add, absorb and deflect sound by the presence and movement of their foliage and branches. Plants are particularly useful in noise control when joined with landforms. Plants can remove and trap pollutants from the air as well as introduce fragrance or odors from flowers or foliage, such as the spicy scented leaves of the bayberry.
Figure. 4. This design, employing plants and pavements, emphasizes a functional and important entry approach by directing traffic to the main entry.
For climate control, deciduous shade trees might be used to screen the hot summer sun or in winter permit the solar radiation to penetrate to the ground, or to the walls and windows of a building. Large shrubs can serve as windbreaks to reduce wind velocities. Changes in solar radiation or light levels are also possible with shading.
The aesthetic functions of plants are the easiest to understand. Plants traditionally have been used for beautification; unfortunately, most people think this is the only reason to landscape with plants.
Aesthetically, plants can become a piece of living sculpture. When placed against a plain wall or fence, they create an interesting shadow pattern of branches and leaves. Plants can be used as background for other plantings, or arranged to provide visual coherence to unrelated objects or structures. They provide suitable environments for birds and other wildlife, too (Fig. 5).
Plants may be used for diverse purposes in the modern landscape. Rarely should plants be simply ornamental; rather, they should serve multiple roles, making the modern landscape both attractive and functional.
Figure 5. Plants can form a living sculpture on their own, or help soften surrounding architecture.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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