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The Trouble with Poor Pruning

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Thursday, March 8, 2007

I had one of my maple trees pruned about six years ago and there is a great deal of decay on the limbs that were pruned. Some of the stubs left from pruning are now decaying. Other limbs that were pruned flush have not healed over and there is now rot within the tree. I believe the tree is a Norway maple and it does not look as good as my other maple trees. The tree is not far from my driveway and I fear that it may fall on one of our vehicles if the decay gets worse. Should I remove the tree?

-- R.S. Manalapan

I would advise having your maple tree examined by a certified tree expert to determine if the tree needs to be removed or pruned properly by a qualified arborist. Hazard trees present an unnecessary risk to people or property. Based on your description, your maple tree was not pruned properly. It is a mistake to leave limb stubs on a tree or to prune flush against the main trunk. Limb stubs can become infected with various fungi that grow through the remaining limb and into the heartwood or center of the main tree trunk. The same type of fungal rot also can occur when tree limbs are cut flush with the trunk.

To encourage proper healing, pruning should be made at the same angle as the tree branch and above the branch-bark ridge -- where the branch and the trunk push up bark between them. Proper pruning at the top of the branch-bark ridge will encourage rapid healing of the cut surface and prevent fungal infection and rot.

Before hiring a tree service, ask for references and talk to some previous customers and examine their pruning work. Look for companies with certified tree experts or arborists who have expertise in pruning large trees. Make certain the company has adequate insurance to cover any damage that may occur as they work.

Improper pruning can destroy valuable landscape trees, pose unnecessary risks and detract from property values. Remember the commonly held belief that your landscape can contribute 30 percent or more to your property value. For a list of questions to consider before hiring a landscaper or tree-care company, be sure to visit our Web sites. Log on to www.ifplantscouldtalk.rutgers.edu or www.rce.rutgers.edu for more information on pruning and tree care.