The method of pruning a tree or shrub depends on the size and number of branches to be removed. Limbs are pruned from trees with a technique called jump-cutting. This method allows a scaffold limb to be removed without taking a long slice of bark with it when it falls. A jump – cut requires three cuts for the safe removal of a limb (Figure 11—12). The final cut should remove the stub of the limb close to the trunk, but not directly against it. Until recently, the wound would then be covered with
cut at A allows the limb to snap off after a cut at B without stripping bark from the trunk as it falls. The final cut at C removes the stub. (Delmar/Cengage Learning)
a wound paint to make it less conspicuous until the plant has time to heal. However, recent research has suggested that wound paints may actually delay healing of plant tissue. Where this is suspected, the landscaper should not use them.
When shrubs are pruned, one of two techniques is used. Thinning out is the removal of a shrub branch at or near the crown. It is the major means of removing old wood from a shrub while retaining the desired shape and size. Heading back is the shortening, rather than total removal, of a twig. It is a means of reducing the size of a shrub. In cases where shrubs have become tall and sparse, a combination of thinning out and heading back can rejuvenate an old planting (Figures 11-13 and 11-14).
In heading back, the location of the cut is important (Figure 11-15). If too much wood is left above the bud, the twig will die from the point of the cut back to the bud, but the cut may not heal quickly enough to prevent insect and pathogen entry. Also, the woody stub itself may decay later. A cut below the bud will cause the bud to dry out and possibly die. The cut should be made just above the bud and parallel to the direction in which the bud is pointing. The cut should be close enough to the living tissue to heal over quickly but not so close to the bud that it promotes drying. The direction in which the branch of a plant grows can be guided by good pruning techniques. Branches growing into the plant can be discouraged by the selection of an outward-pointing bud when heading back (Figure 11-16). If the twig has an opposite bud arrangement, the unnecessary one is removed.
Heading Back. This method involves trimming back terminal growth to maintain desired shrub size and form. It encourages more compact foliage development by allowing development of lateral growth. This is the preferred method for controlling the size and shape of shrubs and for maintaining hedges.
figure 11-13. The techniques of thinning out and heading back (Delmar/Cengage Learning)
figure 11-15. Where to prune the twig (Delmar/ Cengage Learning)