The operation of pruning to produce topiary effects is one that requires much more careful attention and more frequent pruning than almost any other type of pruning work, with the exception of possibly some hedges such as privet hedges, where it is necessary to maintain a constant, even effect. The yew and boxwood which are used for the most permanent effects in topiary work can be pruned to best advantage during the latter part of June and the early part of July, at which time all the new growth should be cut back as far as the older growth, which consists of darker green leaves. Thisv allows opportunity for new shoots to develop within the old growth and thicken the mass. Many plants used for such topiary effects as ovals, spheres, pyramids, cones, spirals, etc., can be given a thorough trimming when the trees are young. The subsequent growth (if the loose-growing tips are kept cut back) will continue to increase the dimensions of these designs in an interesting way. The key to successful topiary effects is the accurate shape to which the tree is trimmed when the first pruning work on the specimen is undertaken.
Ornamental flowering shrubs may be pruned at any season of the year if no consideration is given to the question of flower production. Wounds made by pruning will heal, however, better during the growing season. Late summer pruning will sometimes encourage a new and vigorous growth which does not thoroughly ripen during the late summer and fall months, and is consequently exposed to the danger of winter-killing. Late summer pruning should accordingly not be practised especially on semi-hardy plants. During wet seasons, and when plants are over-supplied with food, summer pruning may be resorted to, in order to restrain succulent and weak growth.
Many shrubs possess a greater or less value for their flowering habits.
The following are a series of memorandums explanatory of the drawings shown on Plate No. V, illustrating various methods of pruning trees and shrubs.
A large, overgrown, and "leggy" shrub with some new long shoots growing from the base of the plant. In such overgrown plants as these all of the wood which produces flowers is in the top branches at the ends of the old wood and the shrub presents a very bare effect at its base.
The same shrub as shown under "A", but pruned for the purpose of allowing new shoots to develop from the base of the shrub and to permit a new top at a normal height, thus renovating the entire shrub during a period of two or three years.
The same shrub as in "A", showing its development after proper pruning. This produces new flowering wood and a more natural and even development of the entire shrub, which insures a better bloom and a more satisfactory effect.
The same shrub as under "A", but incorrectly pruned or "sheared" in accordance with the method of unintelligently removing all wood, new and old, at a uniform height, irrespective of flowering habits or other habits of growth of the shrub.
The same shrub as under "A", showing the development in its growth after incorrect pruning (A-3). Note that most of the new growth has developed on the old wood, producing a broom effect at the top and a "leggy" condition at the base of the shrub. Such plants cannot grow normally or produce normal flower effects.
This illustration shows the hybrid tea rose pruned to produce an abundance of flowers but not necessarily large individual blooms. The portion in light lines shows the branches to be removed. c-1
This illustration shows the correct series of cuts to be made in removing large branches at a point close to the trunk of the trees (1 is the first cut to be made, or the under cut. 2 is the second cut to be made, or the upper cut. 3 is the final cut to be made, or the close cut). Note also the healing over of a correctly made cut.
This illustration shows the incorrect method of making a cut in one operation, frequently causing the splitting down of the branch. Note also the attempt to heal an incorrect cut, which was not made sufficiently close to the trunk. The bark on such cuts dies back to the trunk and the new healing bark cannot grow over the wound.
Shows correct and incorrect methods of shearing or pruning hedges.
Shows the correct method known as the ovoid cross section (D-1); the truncated cross section (D-2); and the rectangular cross section (D-3). As a result of each of these methods of pruning the hedge produces a solid foliage effect at its base.
These illustrate incorrect methods of pruning known as the inverted pyramidal cross section and the inverted cone cross section, both of which methods resulting in a wide top and a narrow base in the cross section of the hedge produce a bare effect at the base and give little foliage.
Plate V. The correct pruning of trees and shrubs is a great factor in the successful maintenance of landscape plantings. These diagrammatic drawings, together with the explanations on the opposite page, illustrate correct and incorrect methods of pruning.
There are two types of shrubs (Chapter XLII (Pruning Requirements)-A, Page 296), one of which is the spring or early-flowering shrubs, such as Van Houtte's spirea, weigela, snowball, and most golden-bells, producing flowers on wood formed during the previous year. The other type consists of plants which produce flowers during the late summer and fall on the growth of the current year. This type includes the rose of Sharon, the hydrangea, and the common elder. The general rule for the pruning of flowering trees and shrubs, in order to encourage the development of more flowers, is to prune soon after flowering. Unless one has a definite knowledge of shrubs, this rule should be applied literally. The other rule is that spring-flowering shrubs should be pruned in the early summer immediately after they are through flowering, and the summer-flowering shrubs can be pruned to the best advantage in the late winter and early spring before growth has commenced, to avoid the possibilities of winter-killing. Lilacs also should be pruned during the early part of the summer and shortly after the blooming period is complete and in every instance before the seed pods have formed.
Spring-blooming plants should be pruned within a week after the blossoms fall to encourage a summer growth of budded wood which will be well ripened by winter.
Summer-blooming plants may be pruned either in the late summer or just before spring growth begins, to force a new spring growth upon which summer flowers appear. Late summer pruning is never advisable. Some shrubs, such as lilacs, flowering dogwoods, and rhododendrons should not be pruned except to remove dead and diseased branches, or branches that interfere with the development of the plants. Deciduous shrubs of which the wood has become incurably affected with scale may, however, be revivified by being cut down to the ground. In the case of plants that form ornamental fruit the branches should not be cut back far, nor the pruning done after the fruit buds have formed.
Any dead or dying wood should be removed as soon as noticed. In the case of summer-blooming shrubs pruning is best done in the early spring after the leaves appear, in order to remove winter-killed tips.
Old wood should be cut out to prevent shrubs from getting "leggy, i. e., having all top with no foliage around the base. In removing old wood, cut to the base of the plant; otherwise sprouts will shoot up from stumps and fail as the latter decay. New growth should always be encouraged from the roots. Cutting back all branches, or giving shrubs an even shearing should be avoided, as strong shoots will develop and cause a too succulent and unbalanced top growth (See Plate V). With transplanted stock a general rule is to remove about one-fourth of the wood, to offset the loss of roots. Root pruning for shrubs is similar to that of trees (See Chapter on "Planting and Transplanting").
Old shrubs and overgrown material should be thinned out by removing some branches to the base of the plant. This will allow sun and air to reach the base of the plant and encourage growth at the bottom. The dogwoods, globe flowers, and similar shrubs lose the bright colour of their wood as they age. The old wood should be removed to encourage new growth.