It often becomes necessary to find some fast-growing type of tree or shrub to produce an immediate screen. This is especially true in the development of new landscapes where a foliage effect is desired and the more permanent types of shrubs in the plantation require a longer period to produce the desired effect. In such instances the more rapid-growing types of shrubs may be planted and removed after the first one or two years, at which time the more permanent types have developed far enough so that during the succeeding years they will produce the effect which the designer had in mind when they were first selected. The great danger in using quick-growing types of temporary materials for immediate effects lies in the fact that for the success of such plantations the owner must have the "courage of his convictions" and remove the temporary types of material when the time comes that they are beginning to crowd and to injure the more permanent types.
In other instances, where it is necessary to screen service buildings or blank walls of other buildings such quick-growing types of trees and shrubs as the ailanthus, poplars, willows, and elders may be planted. The ailanthus especially is used to form a mass of foliage against service buildings and blank walls during the summe rmonths, but this tree is cut back each year to a height of three or four feet and the new growth produces the effect during the next year.
The fast-growing types of trees and shrubs often used to produce quick effects are correspondingly short lived. Those trees and shrubs which grow rapidly, mature and decay nearly as rapidly. Very few of these types should be placed in permanent plantings.
This list consists of two distinct groups of fast-growing material: that group of which the ailanthus, poplar, willow, and elder are typical, being the very rapid-growing types of material, and that group of which the remaining trees and shrubs are typical being rapid-growing types which are more or less permanent in their character of growth. The types contained in this last group establish themselves much more quickly than trees and shrubs of a similar kind, which require a longer period after transplanting before making a normal growth.
Such shrubs as the weigela, the ninebark, and the privet are often used to obtain quick mass effects of foliage around the base of buildings in locations where the slower-growing types of shrubs, such as lilacs, bridal wreaths, and snowballs would require a much longer time to develop a similar effect.