An arborist offered to “top” my shade tree that has grown so large that branches touch the house. Should I have him do that?
Topping is cutting all tree branches back to an arbitrary height. Other names for topping include “heading,” “tipping,” “hat-racking,” and “rounding over.”
Never do business with anyone who offers or advertises topping. Topping violates all pruning rules. It causes several problems
1. Starvation. Topping removes so much of the crown that it upsets an older tree’s well-developed crown-to-root ratio and temporarily cuts off its food-making ability. The tree goes into shock and readily produces new shoots.
2. Weak new growth. The branches that sprout following topping are much more weakly attached than a naturally developed branch. Rot at the severed end of the limb can make a bad situation even worse.
3. Rapid new growth. The goal of topping is usually to control the height and spread of a tree. However, it usually has exactly the opposite effect! After topping, trees vigorously re-sprout. The resulting sprouts are far more numerous than the normal new growth and they elongate so rapidly that the tree returns to its original height in a very short time.
4. Insects and disease. The large stubs of a topped tree have a difficult time sealing. Thus the stubs are highly vulnerable to insect invasion and decay.
It sounds to me like all you need to do is shorten or remove a few branches that are touching the house and do some selective thinning of other branches to balance the tree shape.
Good pruning practices rarely remove more than one-quarter of the crown, which does not seriously interfere with the ability of a tree’s leafy crown to manufacture food. Individual branches are pruned according to the following principles: Normally when branches are too crowded and grow into each other, entire branches are removed back to their origin. Keep the branch which has an angle with the trunk closest to 90 degrees. Narrow crotch angles of less than 45 degrees are weaker and easily broken. Side branches off the scaffold branches which are growing in toward the center of the tree or are growing into each other are usually removed at their source. If you decide to shorten a branch, prune just above a side branch if possible. If no side branches are present, prune just above a bud. Stubs left above buds or branches will die and are an open invitation to rot and insects.
Large trees are best pruned by a qualified arborist. Check with your city forester for recommendations on qualified arborists.
