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Guidelines For Tree & Shrub Pruning

The purpose of tree or shrub pruning is to promote the growth of a sturdy and healthy plant. Before starting to prune, the homeowner should give consideration to the following guidelines.

WARNING

If trees are in contact with or close to utility services

DO NOT ATTEMPT TO PRUNE THESE TREES

Consult Your Utility!

Introduction:

Always prune your trees and shrubs based on this order and methodology:

U-shaped tree limb joint
Figure 47 - U-shaped tree limb joint
V-shaped tree limb joint
Figure 48 - V-shaped tree limb joint
  1. Safety pruning,
  2. Health pruning,
  3. Aesthetic pruning.

Pruning trees will always weaken their resistance, in some degree, to disease and pests. Because of this the homeowner should not prune certain species of trees in certain seasons. If Oak wilt is in your neighborhood, do not trim Oaks in spring or early summer. Trees that are at risk of contracting fireblight should be pruned in their respective dormant periods.

Pruning Limbs & Branches By Size:

  1. Limbs that are less than 2 inches in diameter - proceed,
  2. Limbs that are 2 inches to 5 inches in diameter - take time to consider what you are proposing,
  3. Limbs that are larger than 5 inches in diameter - should only be pruned for a valid reason.

Thinning The Canopy:

Follow these guidelines for thinning the canopy:

  • When pruning to thin the crown or canopy always start at the top
  • Limbs that have U-shaped connections, as shown in Figure 47, should be retained. Limbs with V-shaped connections as shown in Figure 48 should be removed.
  • Horizontal limbs should be evenly spaced on the trunk of an not yet mature tree.
  • Limbs that touch other limbs or branches should be removed.
  • Horizontal limbs should never be larger than 3/4 of the size of the tree trunk.
  • The maximum pruning of a tree's canopy should not exceed 1/4 of the living canopy in any one year. Additional pruning if required should be done in subsequent years.

Raising The Canopy:

The tree's total height should never exceed the ratio of 1/3 bare trunk and 2/3 canopy, as shown in Figure 49. The tree needs the canopy to develop a strong trunk.

Always prune away root sprouts (Figure 50) and epicormic sprouts (Figure 51).

Raising the tree's canopy
Figure 49 - Raising the tree's canopy
Tree root sprouts
Figure 50 - Tree root sprouts
Epicormic sprouts

Figure 51 - Epicormic sprouts

Reducing The Width Of The Canopy:

Reducing the width of the canopy should only be done as a last resort. Pruning cuts should be on horizontal limbs that are no less than 2/3 of the diameter of the stem to be taken off.

Any time that it is required to remove in excess of half of the living foliage from any one limb, it is wiser to prune the entire limb.

More detailed information on pruning trees.