In the Garden:
Southwestern Deserts
August, 2005
Regional Report

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1856

Use a three-part cut to prevent bark from tearing like this.

Pruning Storm-Damaged Trees

Am I the only one whose heart skips a beat when I see dreadful pruning jobs? It seems like it, as mutilated trees and shrubs abound wherever I go. Now that fierce summer monsoon winds have arrived to snap tree limbs like toothpicks, it's a good time to review a few pruning guidelines.

Beautiful trees add significantly to the value of a property (some estimates are 15 to 20 percent) so you don't want to increase the damage or hasten the tree's death if you can prevent it. If damage is severe to a mature tree, and you're inexperienced, it's worthwhile to consult a certified arborist. Many general landscape maintenance workers have no training in this area and make matters worse.

I'll give you an example. Rather than using a pruning saw to make a clean cut, landscape workers in my neighborhood tugged on a broken limb to remove it. The limb didn't break free without the bark ripping several feet down the trunk. The tree is now permanently disfigured, with an open wound for pests and diseases to enter. Their job was to "clean up" and they didn't have the experience or knowledge to realize they were actually creating a mess.

Make a Proper Cut
Broken limbs should be cut back to the point of origin where the branch meets the trunk or to the next larger branch. At this juncture, trees have specialized meristematic tissue, which aids in healing pruning wounds. The tissue basically grows over and seals off the cut. Don't apply sealants or paints of any kind to pruning cuts, as it interferes with the tree's natural healing abilities.

Cut along a straight line that connects the "branch bark ridge" and the "branch collar." The branch bark ridge is a raised furrow of bark on the top of the branch. It is in the angle where the branch and the trunk meet. The branch collar is a raised furrow of bark on the underside of the branch. The meristematic tissue is within this collar. So you want to cut a line between these two areas. Flush cuts -- as close to the trunk as possible -- are no longer recommended. They remove the meristematic tissue that helps the tree heal the wound. For the same reason, don't leave stubs. The meristematic tissue can't reach out along stubs to seal the wound.

Three-part Cut for Heavy Limbs
When removing large or heavy limbs that are about 1-1/2 inches or more in diameter, the weight of the limb will easily cause the bark to tear down the trunk if you make just one cut. To prevent bark from tearing, arborists recommend a three-part cut. First, using a pruning saw, make an undercut on the bottom of the branch 6 to 12 inches from the trunk. Saw through about 1/3 of the branch. Next, several inches farther out on the branch, saw through it completely. This drops the majority of the weight and the undercut prevents tearing. Make the final pruning cut at the branch collar, as described above.

Pruning is both art and science, and it's challenging to develop the knack without seeing it done. Check with your local extension office for classes or demonstrations. Look at reference books and Web sites to learn more.


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