Both foliage mass and tree trunks can be used to enframe views (Figure 11-40). Plants also require proper conditions for growth. Figure 11-34
Tall shrubs can be used by themselves or in combination with other plants to enclose space. The tall shrubs can function like walls below the ceiling of the canopy overhead. Plant materials also require some time to reach mature height and may vary in their density with the season if they are deciduous. After the trees have been arranged in the design, smaller plant materials can be located to complement the spatial organization of the trees. Plant materials can be used architecturally in any design theme. Spacing. First, the trunks of trees can suggest the edges of space, particularly when they are massed or
Trees can be used to create walls and ceilings in outdoor spaces. A bed of ground cover next to an area of lawn or pavement can imply an edge to a space (Figure 11-36). enclosure whereas deciduous plants can be used to enclose a space during the late spring, summer, and early autumn months of the year. Two different levels of spatial enclosure are possible (Figure 11-29). Tall shrubs that are 6 feet or more in height enclose space at a lower level than trees. Trees can also be used to furnish ceilings over outdoor rooms. Plants may also give a sense of privacy by screening views to the neighbor’s outside living and entertaining space or recreational lawn area (Figure 11-39). To create complete enclosure, smaller trees or shrubs must be used in association with the tree trunks (bottom of Figure 11-28). The second way trees create space in the vertical plane is by means of their foliage mass. As discussed in Chapter 2, a vegetative ceiling can provide a sense of vertical scale in an outdoor space, a feeling of comfort, and shade. Figure 11-28
Tree trunks can be used to imply vertical planes in outdoor spaces. lined up (top of Figure 11—28). Trees should be placed in a structured alignment in an axial design theme and in a flowing composition in a curvilinear theme (Figure 11-33). Walls and fences, on the other hand, give instant screening and separation. complete enclosure. Figure 11-31
Different variables influence how tree canopies create the overhead plane of outdoor space. Large trees provide walls of foliage that define the upper limits of outdoor spaces, while smaller trees create lower walls for enclosure at eye level. The tree trunks can act like the columns in a building, subtly separating one room from another. Figure 11-32 shows both a bad and a good example of coordinating trees with the underlying ground plane. In creating vertical enclosure of outdoor space with trees, the designer should decide whether year – round or seasonal enclosure is desired. It should be noted that the term architectural refers only to enclosing space and does not mean using plants in straight lines or formal layouts. Partial containment is often a good balance between complete enclosure (with no views) and no enclosure (with unlimited views in all directions). Trees should not be scattered indiscriminately in a design but should be massed together so their trunks and foliage mass reinforce the base plane patterns. Evergreen plant materials are usually more desirable for screening views than deciduous plants because they furnish year-round screening,
though a mixture of evergreen and deciduous plants provides the most visual balance and interest. Tree trunks only imply the edge of a space because views are not completely contained within the space. In defining space with trees, thought should be given to coordinating their placement with the desired design theme and grading of the ground plane. Large trees are best for outdoor rooms where views below the tree canopy are desired, while smaller trees are appropriate where walls of foliage are needed at eye level. Ground cover, spreading plants growing to a maximum height of 1 foot, low annuals, and perennials can likewise imply the edges of space. Plant materials can function as floors, walls, and ceilings to establish the spatial envelope of a residential design, just as the architectural components of a building create indoor rooms. In comparison to steep slopes or berms, plant materials take up less room and provide more height (Figure 11-38). The residential site designer can work with these two planes to make varied degrees of spatial enclosure (Figure 11-30). On a residential site, plants can screen undesirable off-site views to neighboring driveways, backyards, and storage areas or to unsightly on-site elements such as an air conditioner, vegetable garden, and so on. Creating Space Plant materials of all sizes and types can be used to define outdoor space. In the vertical plane, trees can define space by two different means. These uses are frequently desirable where people spend time sitting and socializing in the outdoors, such as in the outdoor entry foyer, the outdoor living and entertaining space, or other sitting and gathering spaces.