Pruning Trees - Guidelines

Pruning Intro - Pruning Approaches - Pruning Cuts - Pruning Practices - When to Prune - Pruning Tools - Treating Wounds - Pruning Guidelines - Pruning Glossary

To encourage the development of a strong, healthy tree, consider the following guidelines when pruning.

General

• Prune first for safety, next for health, and finally for aesthetics.
• Never prune trees that are touching or near utility lines; instead consult your local utility company.
• Avoid pruning trees when you might increase susceptibility to important pests (e.g. in areas where oak wilt exists, avoid pruning oaks in the spring and early summer; prune trees susceptible to fireblight only during the dormant season).
• Use the following decision guide for size of branches to be removed:
  1. under 5 cm diameter - go ahead,
  2. between 5 and 10 cm diameter - think twice, and
  3. greater than 10 cm diameter - have a good reason.

Crown Thinning

• Assess how a tree will be pruned from the top down.
• Favor branches with strong, U- shaped angles of attachment. Remove branches with weak, V-shaped angles of attachment and/or included bark.
• Ideally, lateral branches should be evenly spaced on the main stem of young trees.
• Remove any branches that rub or cross another branch.
• Make sure that lateral branches are no more than one-half to three-quarters of the diameter of the stem to discourage the development of co-dominant stems.
• Do not remove more than one- quarter of the living crown of a tree at one time. If it is necessary to remove more, do it over successive years.

Crown Raising

• Always maintain live branches on at least two-thirds of a tree's total height. Removing too many lower branches will hinder the development of a strong stem.
• Remove basal sprouts and vigorous epicormic sprouts.

Crown Reduction

• Use crown reduction pruning only when absolutely necessary. Make the pruning cut at a lateral branch that is at least one-third the diameter of the stem to be removed.
• If it is necessary to remove more than half of the foliage from a branch, remove the entire branch.

Pruning Intro - Pruning Approaches - Pruning Cuts - Pruning Practices - When to Prune - Pruning Tools - Treating Wounds - Pruning Guidelines - Pruning Glossary

Courtesy of the US Dept. of Agriculture.