There are two kinds of specimen plants, those which are used as single specimens, with full space allowed for their normal development, and those which are used as accent plants in masses of border planting, because, as such, on account of their flowering and foliage habits, they lend a definite touch of interest to the plantation.
The various plants included in this group are those which have a normal symmetrical habit of growth, or those which can easily be kept in a neat, symmetrical outline. In order fully to understand the difference between specimen trees and shrubs, and trees and shrubs for border plantings in groups, the reader should first know that many of our trees and shrubs are not adapted to so-called "mass plantings." Under the crowded condition of mass plantings these trees and shrubs do not produce any of their interesting characteristics of flowers and general outline. Much dead growth becomes evident on account of the exclusion of light and air necessary for their proper development. It is necessary to examine but a few plantations further to know that many trees and shrubs most interesting when used as individual specimens or as groups of two or three plants make a most uninteresting group when massed in quantity.
In general it may be said that specimen piants are used as such because of their fruiting habit, flowering habit, interesting outline, or general foliage effect, which is evidenced at its best when the material is planted as individual specimens.
So-called specimen plants in this group are often used as accent plants in the larger and massed plantations, because of the quality of the flowers, the colour of the foliage, the habit of their growth, or the texture and colour of twigs. Many specimen plants can be used to good advantage scattered here and there in the border plantations to emphasize one or more of these interesting characteristics, and they sometimes are even more effectively used in this way as accent plants than as specimen plants on the lawn.
Whenever material is selected as specimen material it should be planted as such, and space should be provided wherein the plants can develop their individual and normal characteristic habits of growth; but when they are used as accent plants it is not so essential to provide space for normal development. Illustrations of this may be seen in the use of the burning bush, the sourwood, and the silver bell.