AMES, Iowa--Major thunderstorms and tornados cause damage in sections of Iowa several times every year. If you live in an area hit by these storms, you should look at the tree damage caused by the storms. Tree damage ranges from a few broken branches to total destruction, said Jeffrey Iles, Iowa State University professor of horticulture and Extension tree specialist.

"As you assess the damage of your trees, look for cracks in the branches or trunks, broken and hanging branches and trees leaning that were straight before the storm. With high winds, it is possible that some trees sustained root damage, which often is indicated by the appearance of bumps in the ground caused by breaking or moving roots," Iles said.

Trees and/or tree branches that have serious structural damage such as splits and cracks could potentially be hazardous. To ensure safety and to prevent further property damage, remove all hazardous trees and branches immediately. In general, trees that have been uprooted, sustained trunk failure or have broken branches that account for more than 50 percent of the crown should be removed immediately.

"If you are not sure about removal, it is OK to leave a damaged tree a year or two to see how it responds to the damage, as long as the tree is still structurally sound," Iles said.

Damaged trees that will not be removed will require some corrective pruning.  And even though timing for pruning might not always be ideal, damaged trees should be pruned as soon as possible. When removing branches, do not cut flush to the stem or leave large stubs; instead remove branches just outside the branch collar.

"Do not have your damaged tree topped. Topping is basically the indiscriminate removal of branches with no consideration of proper cuts that promote proper tree response," Iles said. "When trees are topped, they will respond with a flush of new growth that is weakly attached to the open pruning wounds, and susceptible to breakage and decay."

Also, pruning paints and wound dressings are no longer recommended for use on tree wounds in most cases. One exception to this rule is in the case of oak trees that have open wounds during the growing season. In Iowa, the disease oak wilt is present and can potentially spread through open wounds. So, in the case of oaks, pruning paints may reduce the potential of disease spread, he said.

For more information on taking care of your damaged tree or trees, contact your local Iowa State University Extension office.

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Updated 3/08

Contacts: Jeffrey Iles, Horticulture, (515) 294-3718, iles@iastate.edu

Del Marks, Extension Communications and External Relations, (515) 294-9807, delmarks@iastate.edu