Shrubs are used in four broad ways: for boundaries, for partitions and backgrounds, for specimens and for foundation plantings. We have discussed these uses of shrubs and the characteristics demanded by each use. Even at the risk of repetition, further discussion with the particular plans in mind may be helpful.
Boundary plantings are used to give privacy and to screen from view any unsightly objects beyond. Also, they tie the whole garden together to give unity, and they act as a background and frame for the garden displays.
Boundary plants need to be dense enough and high enough to shut off the view, with some variety in height to make the skyline interesting. Sometimes it is a good idea to leave gaps in the planting, to show desirable views beyond the boundaries.
As mass effect is desired, plant shrubs in groups of one variety rather than single plants of many sorts. Choose the shrubs for their rapid growth, spreading habit and mid-green foliage rather than for distinctive features. Wherever bloom occurs it should be in large enough masses to be effective at the distance from which it will be seen. Bloom, of course, is always attractive but in large gardens it is not as important in boundary plantings as in parts of the garden where it will be seen in more detail.
On small city lots we cannot hope to attain complete privacy or to screen the view of all surrounding buildings. On some lots the boundary planting takes the form of a hedge, or a fence on which climbers are grown. On others it is made up of groups of shrubs that not only back up the bright displays of the garden but to a great extent form the displays themselves.
Partitions and Backgrounds
Plantings separating small lots are more like partitions than boundaries.
The purpose of partitions, or background, plantings is to separate one garden area from another. Here, bloom and other distinctive features are important as the shrubs are close at hand and consequently are seen in detail.
Keep in mind that partitions and backgrounds are seen in elevation, and in your plans arrange them so that they will be most pleasing at maturity. There will be points where you need boldness and increased height in the skyline. Here you should use “dominant” plants – small trees or large shrubs that have coarse foliage and a dense appearance ó whose height and texture makes them stand out above their fellows. These break the partition into sections or pictures. Usually the center of interest in each of these small pictures consists of low-growing plants, such as those that spread horizontally or have some other particularly attractive feature. These we call “interest” plants. They are backed up and flanked by “fillers,” average sorts of plants whose function is to enhance and connect the other two.
In all good shrub grouping in informal gardens, harmony is the rule, contrast the exception. There should be harmony of form, and of color and texture of foliage, with strong contrast of form and texture used only at strategic points. Foliage color should blend gradually with the bright, warm greens near at hand and dark greens, blue-greens and gray-greens farther away. This gives the impression of added distance.
Texture, too, may be used to create illusions of distance or to emphasize certain points. Large foliage and coarse twigs like the bamboo palm plant are seen more clearly than fine foliage and twigs and, consequently, seem to be closer. For this reason large shrubs of coarse texture make large spaces seem smaller. Similarly, a coarse shrub at the front of a border of fine-textured shrubs stands out very distinctly, and fine shrubs backed by coarser ones appear flat.
Shrubs used as specimens, or accent points, in the garden lend emphasis to particular features of the design.