February 10, 2021
Topping is the drastic removal or cutting back of large branches in mature trees. The tree is sheared like a hedge and the main branches are cut to stubs. Many homeowners top trees when they reach heights considered unsafe fearing a strong wind might blow large trees over. However, the extensive root system of a healthy tree provides adequate support for the tree. Below are a number of reasons why deciduous trees should not be topped.
Starvation: Trees need leaves to manufacture starches during photosynthesis. A tree’s transport system moves starches from the leaves to the roots. Topping removes so much of the leafy crown that a tree may be unable to provide the roots with essential nutrients. This in turn prevents roots from growing and transporting nutrients and water to leaves. Good pruning practices rarely remove more than 1/4 to 1/3 of the leafy crown.
Shock: The tree crown acts like an umbrella, shading the bark from the direct sunlight of summer. Sudden removal of the leafy protective layer exposes the bark to sunscald. Neighboring trees used to shady conditions may be adversely affected. Poor health and death often occur.
Insects and disease: Large wounds resulting from tree topping have difficulty closing. The location and size of the cuts prevent the tree’s natural defense system from functioning. Stubs are open wounds that invite insect invasions and the spread of decay fungi. If decay is already present in the limb, cutting will only speed the spread of decay.
Weak limbs: Many new limbs sprouting from the cut of the larger branch are weakly attached to the parent branch. Growing limbs attach to the larger branch with layers of wood overlapping year after year. Limbs gradually enlarge with the parent stem. Limbs growing from large cut areas develop from that point only and not as an extension of the entire parent branch. In some instances, the attachment to the parent stem involves less than one inch of wood.
Rapid new growth: People believe they need to top their trees to control the height and spread of a tree. Actually, trees respond rapidly to the injury by producing many, long sprouts. The result is a bushier tree that quickly regains the height it once had.
Tree death: Some species of trees do not tolerate topping. Beeches, for example, sprout little after a severe pruning. The lack of foliage severely reduces the tree’s ability to capture sunlight and turn it into glucose.
Ugliness: A topped tree is a disfigured tree. Even with regrowth, it never regains the grace and beauty of its species. The landscape and the community are robbed of a valuable asset.
Cost: Topping may reduce cost and time for the moment, but actual costs can be seen in reduced property values, removal and replacement cost when the tree dies, loss of other trees and shrubs succumbing to changed light conditions, risk of liability from weakened branches and increased future pruning costs.
The complete article comes from the Purdue University Forestry Department and is available.
Montana State University, U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.