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Ask an Arborist: What Are the Rules of Pruning?

After selecting the right tree and carefully planting it, early pruning is the most important thing you can do for a young tree.
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hands holding pruning shears

The Right Approach

Tree pruning, trimming, or cutting is an ongoing process throughout the life of your tree. After selecting the right tree and carefully planting it, early pruning is the most important thing you can do for a young tree.

But one of the most common mistakes made in pruning trees is removing too many branches, which can impact the growth rate of the tree. So here are five rules (or “factors”) — a phrase first coined by Mark Peterson of the San Antonio Water System — you can follow to make sure the pruning “dose” is directed in the most effective manner, without impacting the rate of growth.

closeup of hands holding shears

Five Factors for Form and Function

  1. Branches and leaves will occupy at least ⅔ of total height.
  2. All branches will be <½ the diameter of the trunk, at point of attachment, this keeps branches from competing with the trunk.
  3. No more than ⅓ of live foliage will be removed in a year. This is a heavy pruning dose for a young tree; ‘less is more’ in most cases.
  4. All final cuts will be less than 1 inch in diameter, this means cuts close over quickly, limiting chances for decay organisms.
  5. Limit of 5 pruning cuts per year.

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