Pruning Shade Trees

Late winter, February and March, is usually an excellent time to prune deciduous trees. Branches are easier to remove when not weighted down by leaves, and the tree's branching structure is easier to see.

However, following last season's severe drought conditions most landscape trees are stressed, so it's more important than ever to use a critical eye to assess the need for pruning this year, and, if pruning is necessary, use good pruning techniques to avoid causing additional tree stress.

Is Pruning Really Needed?
If your trees are properly shaped, and don't have hazardous branches, or branches obstructing movement and maintenance of your landscape, it would be a good idea to not prune this year. Pruning causes wounds, and stressed trees have less ability to seal off wounded areas. This puts them at greater risk from wood-rot fungi and decay.

Normal branch removal should be done for any dead, damaged or hazardous branches, but do as little additional pruning as possible. If possible, leave major pruning operations for a time after eastern Nebraska has returned to normal precipitation levels.

Don't prune any trees that were planted last summer, or that will be planted this spring. Newly planted trees often suffer from transplant shock, which limits their ability to respond to additional stresses, such as sealing pruning wounds. Their first need is to establish a good root system, that can physically and biologically support the tree, and they need all the photosynthates the tree's foliage can produce to make that happen. Delay pruning of newly planted trees until the second or third year after planting, when hopefully normal rainfall will have returned to eastern Nebraska.

Follow Good Pruning Practices 
If pruning is necessary, is should always be done with an understanding of how trees respond to each cut. Improper pruning can cause damage that will last for the life of the tree, or worse, shorten the tree's life.

Pruning cuts should be made so that only branch wood is removed and the trunk is not injured. If only branch wood is removed, the wound is smaller, the tree will be able to seal the wound more effectively, and the chance of problems with wood decay will be greatly reduced.

To locate the proper place to make a pruning cut, first look for the "branch bark ridge" on the upper surface of the branch where it joins the trunk. This is a line of bark that is pushed up between the branch and trunk as they grow. (Some branch unions will not have this if they did not form properly. Instead the branch will simply press into the supporting stem, forming a sharp V-shaped union.)

On the underside of the branch look also for the "branch collar", which is a slightly swollen area of trunk tissue that wraps around the base of the branch.

A proper pruning cut begins just outside the branch bark ridge and angles down and slightly away from the trunk, avoiding injury to the branch collar.

3-Cut Pruning Method
Large branches should always be pruned using a series of three cuts. The first cut is to the underside of the branch, approximately 8-10 inches from the tree's trunk, and goes less than half way through the branch. The first cut does not remove any of the branch; it's purpose is to prevent the bark from ripping down the side of the tree when the branch falls.

The second cut is made an inch or two further out from the first cut, away from the tree trunk, and removes the majority of the branch. The second cut should be made from the top side of the branch down.

The final cut removes the remaining stump, also going from the top of the branch down, being careful not to cut into either the branch bark ridge or the branch collar.

Pruning Tips:

• Don't make flush cuts that remove the branch collar. Wounds created by flush cuts cause substantially more injury to the tree than wounds left by proper pruning.
• Don't leave long branch stubs. These prevent the formation of a good seal around the wound at the end of the branch stub, and expose the tree to the entry of wood-rot decay fungi.
• Don't remove more than 1/3 of the tree's foliage.
• Don't thin out the center of the tree's canopy. This lessens the tree's ability to function properly during hot, dry periods.
• Don't apply wound dressings to the cut surface. Wound dressings release chemicals that can be harmful to the tree, and hold moisture against the cut surface promoting wood rot. Instead allow the area to dry naturally. The tree will seal off the wounded tissue and begin growing callus tissue to cover it.