Pruning Mature Trees
Pruning Mature Trees
You can improve tree health and appearance by removing limbs that are dead, weak, diseased and insect-infested. This also reduces sources of future infection and infestation.
Large limbs must be cut with a saw. The recommended procedure is to remove a large limb in two steps involving three cuts. Make the first cut on the underside of the branch 1 to 2 feet from the crotch. The under cut should penetrate at least one third of the trunk diameter. Make the second cut 1 to 3 inches farther from the crotch than the first. The limb should split cleanly between the two cuts without tearing the bark on the trunk.
You can then make the third cut at the crotch with less chance of the bark's tearing and leaving a jagged cut surface. The position of this cut is important to ensure rapid healing of the wound.
Many trees form ridges on the top and bottom of branches where they are attached to the trunk. These are called shoulder rings. Pruning cuts should be made between the center ridges of these rings. The cut will not be flush or parallel to the trunk but will be out from it slightly, with the lower edge of the cut farther away from the trunk than the top.
Such a cut will form a smaller wound than a flush cut, and callus tissue will form rapidly to cover the wound. Callus tissue should develop uniformly around the edge of the wound.
Often shoulder rings are not present at branch attachments. The cutting position can be approximated by envisioning a line connecting the point bisecting the top angle of the crotch and a similar point bisecting the lower angle of attachment.
The structural features of a tree may be emphasized by moderate thinning to reduce density. The structure of dogwood, ginkgo and others can be maintained in the landscape by moderate thinning out.
Homeowners often attempt to control the size of trees by pruning. It is best to prune the tree as it begins to reach the desired height. Delaying pruning until the tree is much larger than you want it makes pruning more difficult and pruning cuts harder to hide, and it encourages excessive regrowth.
Thinning-out pruning can be used to reduce the height and spread of a tree. Cut branches to lower laterals (drop crotching). Some limbs may be removed completely. A thinned tree retains its natural shape and is less subject to vigorous watersprouts than a headed or topped tree.
Topping (heading back) is, unfortunately, the most common method of reducing tree size. It is more rapid than thinning, but the results are, in most cases, much less desirable. Regrowth is vigorous and upright from the stubs. The new branches form a compact head and broom-like terminals, and they may be weakly attached to older branches.
Bleeding of pruning wounds can be heavy on certain trees, such as birch, dogwood, sugar maples and elms. Bleeding of susceptible trees can be minimized by making small cuts--less than 3 inches in diameter--and pruning in summer. Bleeding is much more likely if severe pruning is done just before growth begins in the spring. Bleeding doesn't harm the tree, but it it's heavy and persistent, it may injure the bark below the pruning cut and cause slow callusing of the lower wound.
If large limbs need to be removed or if you can't reach the limbs that need pruning, secure the services of a professional landscape manager. Landscape managers are trained in the art of pruning to retain the natural beauty of trees.
