Wounded trees heal themselves

Q. A large limb broke off my tree in a storm. Should I put tree sealant on it to help the tree heal?

Sylvia from Poland

A. No, sealants will not help the tree heal. Many people think treating injuries to trees is like treating injuries to themselves or animals. Putting something over a wound to heal is very different in trees, which respond differently to injuries than we do. Actually, trees don’t heal, they seal., although it’s OK to use either term. Any injury to a tree, such as a broken limb, is a potential entry point for diseases or pests. The tree protects itself from these dangers by isolating the damaged area through physical and chemical processes. These processes result in callus tissue developing at the edge of the wound and gradually expanding toward the center. This process is called compartmentalization.

Scientific studies have been conducted on effectiveness of tree sealants. These are the black tar type sprays you find in some stores. None of the studies have found any benefit to the tree from the use of these products. In fact, use of some types of sealants can inhibit or delay the tree’s natural recovery processes by trapping water inside the wounded area (under the sealant).

If the limb on your tree has not broken completely off from the tree’s trunk, prune it back to the collar of the limb. The collar is the swollen area at the base of the limb. Sometimes, this area looks like wrinkles in the bark. Think of those as the smart cells that grow callus tissue.

If you don’t feel conformable pruning the limb yourself, or if you can’t reach it, we recommend contacting a certified arborist. Certified arborists are members of professional organizations such as the International Society of Arboriculture. They are knowledgeable on all aspects of tree care and have access to current technical information.

The only exception to the rule is the pruning of oak trees in the summer. These wounds can be sealed with latex paint to avoid infection from oak wilt disease.

For more information on caring for tree wounds, see http://go.osu.edu/treewounds.

To learn more about proper pruning of trees, join us at our fall pruning clinic Oct. 17. The details are at http://go.osu.edu/fallprune.

Today’s answer is provided by David Sprague, Ohio State University Extension master gardener volunteer. Call the office hotline at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.