Q. Why is topping bad?
A. The practice of topping is so wide spread that many people believe it is the proper way to prune tree. However, topping can cause a variety of problems in trees, and ultimately cause problems for homeowners.
Q. What’s the difference between topping and pruning?
A. Topping is the excessive and arbitrary removal of all parts of the tree above and beyond a certain height with no regard for the structure or growth pattern of the tree.
Pruning is the selective removal of certain limbs based on the structure and growth pattern of the tree.
Q. When should I prune my tree?
A. A few tree diseases can be spread when pruning wounds allow spores access into the tree. Susceptible trees should not be pruned during active transmission periods.
Heavy pruning just after the spring growth flush should be avoided. This is when trees have just expended a great deal of energy to produce foliage and early shoot growth. Removal of a large percentage of foliage at this time can stress the tree.
Q. How much should be pruned?
A. The amount of live tissue that should be removed depends on the tree size, species, and age, as well as the pruning objectives. Younger trees will tolerate the removal of a higher percentage of living tissue than mature trees. An important principle to remember is that a tree can recover from several small pruning wounds faster than from one large wound.
A common mistake is to remove too much inner foliage and small branches. It is important to maintain an even distribution of foliage along large limbs and in the lower portion of the crown. Over-thinning reduces the tree’s sugar production capacity and can create tip-heavy limbs that are prone to failure.
Mature trees should require little routine pruning. A widely accepted rule of thumb is never to remove more than one fourth of a tree’s leaf bearing crown. In a mature tree, pruning even that much could have negative effects. Removing even a single, large-diameter limb can create a wound that the tree may not be able to close. The older and larger a tree becomes, the less energy it has in reserve to close wounds and defend against decay or insect attack. The pruning of large, mature trees is usually limited to the removal of dead or potentially hazardous limbs.