Tree topping is rookie error

Topping is the indiscriminate cutting of tree limbs to a rounded or other unnatural shape. The intent is to make a tree fit a space in one fell swoop. Other names for topping include stubbing, heading back, dehorning and lopping. Although slight differences exist, all involve limb removal to reduce height without regard for tree growth.

Topping is harmful for many reasons. Good pruning, which seldom removes more than one-fourth of the crown, does not seriously interfere with the tree's ability to make food. Topping, however, removes a significant portion of the photosynthetic leaf area and limits the tree's ability to photosynthesize. The result is slow starvation.

In addition to reducing photosynthetic surfaces, topping also reduces the tree's canopy. The canopy is important because it shields bark tissue from direct rays of the sun. If bark tissue is exposed, sun scald and cracking are more likely.

Topping also is detrimental to tree structure. It causes weak, new limbs to form by forcing growth into poorly developed axillary buds. And if you make a cut in the internodal area, dieback to the previous node is more likely. That creates entry sites for rot and decay and complicates the matter of weak-limb formation.

Large stubs of topped trees are not likely to heal in a reasonable period. The terminal location of the cuts, as well as the large diameter, generally prevents the tree's natural defense system from deterring pests. Remaining stubs are highly vulnerable to insect and disease invasion, especially if decay is already present in the limb.

An obvious reason not to top a tree is that you produce an unattractive landscape feature. Even under the best conditions, with good regrowth, a tree never regains the positive attributes intended by the landscape designer or architect.

The intended goal of topping is to lower the height of the tree and reduce unwanted growth. However, topping is counterproductive to that goal. In fact, in most cases, you'll achieve the opposite effect. Resulting sprouts are far more numerous than the normal new tree growth, and they elongate so rapidly that the tree soon returns to its original height with a far denser crown.

Several alternatives to topping are available, all of which are guided by the general concept of target pruning. The key is to avoid flush-cuts and to identify the branch bark ridge and branch collar in both hardwoods and conifers. Once you identify those anatomical features, you can base pruning on the tree's natural tendency to wall off injured tissue areas and prevent the spread of decay. Proper pruning cuts allow good callus formation and wound healing within a relatively short time.

Drop-crotching is a good alternative to topping, especially where you require vertical height control. Instead of simply cutting limbs indiscriminately, you prune the limbs on the periphery of the tree at their junction with shorter, larger-diameter side branches. A leader always remains and prevents dormant buds from sprouting into rapid new growth.

Drop-crotching can reduce tree size while retaining the natural form. You often can accomplish it without cutting limbs larger than 6 inches in diameter. Obviously, small wounds heal faster than large ones. Under, side and through pruning are variations of drop-crotching that may meet specific purposes.

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