The trees and shrubs in the following list are those whose twigs are coloured sufficiently to make them of value from a landscape standpoint. The colour effect of twigs may be interesting from two points of view: either because of the vivid colouring, such as is seen in the red-twigged dogwood, and in the glossy rose, or of the general tone of colour such as seen in the American olive and the golden-barked willow, in which the colour as a mass is much more effective at a distance than upon close examination.
Many of the interesting shrubs included in this group are oftentimes selected because of the sharp contrast between the colour of their twigs and the white background of snow or the green background of evergreens during the winter months. This is especially true of the birches and the dogwoods. In fact, there is equally as much interest during the winter months in a planting of this kind, properly developed, as in the difference of foliage effects during the summer months. It is a feature of landscape plantings to which very little attention has been given and one which demands careful study in order to be successfully worked out.
On extensive lawn areas, in our parks and large private estates, many specimens of these plants can be tucked away in large groups, where during the winter months the colour effect of the twigs will lend an interesting tone and more feeling of life to the otherwise monotonous effect of the background.
The development of many vistas is oftentimes emphasized through the careful selection of such plants as the birches, willows, and Russian olive, to give the feeling of greater depth in the landscape picture. Such specimens, planted in the immediate background, with a heavy texture of planting in the foreground, will greatly add to the suggested feeling of distance.
The plants included in this group are those which carry an interesting and vivid colour of the branches and twigs throughout the winter months. In the great majority of plants the new twigs show an interesting colour for perhaps part of the year, usually during the early spring months when the sap begins to flow. Later the colour becomes softened or deadened and it does not carry through to the late fall and winter. There are practically no shrubs which can be selected for the colour of their twigs during the summer months. It is not necessary to select plants for this purpose because there are so many other equally interesting effects to be obtained from flowers and foliage.
The first two years' growth, especially the first year's growth on any tree or shrub, the twigs of which have a definite colour, is much brighter than the colour of the twigs after they are more than two years old and are becoming definite branches of the plant. This is a suggestion that severe pruning, or cutting back, will often enhance the effect, as in the case of the red-twigged dogwood.
Twigs are also extremely interesting because of the markings. The tamarix and silky dogwood are types to study in detail as well as being valuable for the mass colour effect seen at a distance.
Colour effects of twigs form the most interesting feature of landscape twig effects, and yet the coverings of older branches and tree trunks on many trees are very effective in summer and winter. Every tree has its individual markings of trunk and branches, of great interest to the landscape student. The white oak, white birch, plane tree, and hackberry, with their peculiar bark, are valuable in landscape planting.