It often happens that large and small places have trees, shrubs, and hedges when purchased, or when the decision is reached to attempt a change for the better. In planning for a change in the landscape expression, it usually happens that many of the old plantings can be utilized. With systematic cutting back and shaping they can be changed into shapely trees and shrubs (147, 152). If the cutting back is done in the dormant season, unshapely trees will soon develop fine tops, if headed back as shown in Fig. 88.
Fig. 88. - An old tree headed back. (After Maynard.)
In some cases a single tree of a large-growing species may be made the centre of a tree group by planting rapid-growing species around it, with undergrowth at the boundaries. In other cases where a shade is needed, a single tree may be given room to shade a corner of the grassy lawn. The single spreading white elm or other fine shade tree may also have place in a grassy dell, or hollow of the grounds, where it has ample room to spread in natural form.
Second-growth timber of varied species is often found on suburban tracts and lots standing too thick for forest or park. On lots some of the trees may be permitted to stand properly thinned and cut back at proper places, but not to interfere with the open lawn or the garden and small fruits in the rear.
In larger places, where groups are wanted, better effects can often be produced for a few years by permitting the greater part of the thriftiest trees to stand thinning gradually as the tops begin to crowd, or as the primal plan of the grounds require.
In starting groups the selection of species should be given attention. Evergreens and deciduous trees should not be mixed in the same group, and such trees as cotton-wood and Lombardy poplar should not be mingled with hard maple and hackberry. The trees and shrub groups should have a harmonious expression. Where not guided by an experienced gardener, the beginner in such work will form tree clumps rather than artistic groups. Many years ago Price wrote: "Natural groups are full of open- ings and hollows, of trees advancing before or retiring behind each other, all productive of intricacy, of variety, of deep shadows, and brilliant lights. In walking about them the form changes at every step, new combinations, new lights and shades, new inlets present themselves in succession. But clumps of trees, like compact bodies of soldiers, resist attacks from all sides. Examine them in every point of view, walk around them - no openings, no vacancy, no stragglers."
Fig. 89. - Large-growing trees arranged in centre of groups.(After Maynard.)
Where trees of the same species are planted in a group, or species similar in size and form, the expression when grown is that of a clump. To avoid this, the skilled planter sets the taller species at a group corner or in the centre, with the smaller and handsomer trees and even large shrubs at the outer irregular edges. Fig. 89, from Maynard's excellent work, gives an idea of this irregular yet natural system of grouping.