Pruning Trees and Shrubs

Deciduous trees and bushy plants. These woody trees and plants are best pruned in early spring while they are still dormant. Some plants, however, go through a process of “bleeding,” when sap runs out of the cuts. While this does not actually harm the plant or tree, it can cause homeowners distress and worry. Therefore, when pruning plants that tend to bleed (such as maple, box elder, black walnut, elm, birch, and honeylocust), it is also acceptable to wait until they are fully leafed out.

Woody bushes like lilac, spirea, mock orange, viburnum, and forsythia should be pruned immediately after blooming. These plants have flowering buds that are produced every previous growing season. And, by pruning such plants directly after they bloom, you will be able to decorate your house with the sweet smelling blossoms on the pruned branches. These small branches, and the thin, small branches of a tree, may be cut with ease all the way through with only a single cut.

When removing a large branch on a tree, however, you will need to make three cuts. This will help you avoid tearing the bark. The first cut is placed on the under side of the branch, and should be located about 12 inches from where the branch meets the trunk. This cut is not very deep — only one-fourth to one-third of the way through the branch. Next, a cut should be made on the topside of the branch, and should be about two inches farther from the trunk than the first cut. Saw completely through the branch on the second cut. The last cut on the branch should be just beyond the branch collar. Leaving a stub encourages disease, and cutting the main trunk produces a wound that heals slower.

Evergreens. Evergreens have a slightly different consideration that the deciduous woody plants. They can be pruned in the early spring, but you should ensure that the new growth has hardened. Evergreens can be pruned practically any time between mid-April and mid-August. It is important to have them trimmed before mid-August because if you wait any longer, they may not recover from their wounds in time to withstand the winter.

Pruning of evergreens should be based upon the presence of their branch foliage. Do not cut beyond the green foliage portion. If you continue to prune, lightly, evergreens such as arborvitaes, yews, and junipers, each summer, they will eventually be a thicker and fuller plant. Failure to prune will result in scraggly-looking trees. Larger junipers and other plants may need a size reduction. In order to do this, follow the branches to be cut until you find new small growth that parallels the branch. Make your cut, diagonally, just beyond the reach of this smaller, parallel branch.

In some evergreens, you will find that the top has been lost due to injury. In such cases, you need to “build” a new top. This can be done by selecting the largest of the whorls nearest the top and by gently bending it up. Tie the branch to an attached brace, using a non-girdling material such as cloth. Then cut back the other lateral branches so that they cannot compete with the branch chosen as the new top. As with deciduous trees, it is important to cut back to a side branch or bud, and to leave no stubs.

No matter what type of tree you are pruning, the practices of topping, hat-racking, and heading are not recommended. These methods of trimming are not true pruning techniques, and they result in small shoots, called suckers, to form near the cut surface. These suckers are weak and rarely attractive, and they can distort the shape of the tree. And once improperly pruned, a tree may never return to its characteristic form.