Winter is the ideal time to prune trees and help prevent the spread of diseases like oak wilt and Dutch elm, according to experts with the Minnesota Department of Natural Resources.
“My rule of thumb is when winter weather conditions are less desirable for humans, the timing for tree pruning is great,” said DNR forestry specialist Randy Schindle. “Pruning in the winter is less risky to tree health, and it’s a good way to get some outdoor exercise and stay warm.”
The reason for wintertime pruning is simple—it minimizes the risk that an open wound could invite decay or insects that carry oak wilt or Dutch elm disease—according to DNR forestry outreach specialist Jennifer Teegarden.
“In the spring and summer, tree sap from open wounds can attract insects that carry oak wilt and Dutch elm disease. The moisture from the sap in a fresh wound can also encourage decay,” Teegarden said. “Another consideration is that when trees lose sap, they lose energy to grow in the spring. Winter pruning reduces sap flow from a wound.”
Winter pruning also allows the wound time to dry out before the sap runs and insects become active. “Much of the sap goes underground into the root system during a typical winter,” Schindle said. “Sap stored in the roots moves to the upper part of the tree when the weather warms up. The more time a tree has to heal before the sap begins to run, the better.”
Tree pruning is done for the following reasons:
- Safety—to remove limbs that hang over walkways or threaten to fall unpredictably.
- Tree health—to remove diseased limbs or crossing and rubbing branches.
- Aesthetics—to enhance the natural form or stimulate flower production.
Tree pruning tips:
- Minimize wound size by trimming branches before they grow to be 2 inches in diameter.
- Save the branch collar—don’t cut flush to the trunk.
- Use the 3-cut method for larger branches.
More tree health tips are available on the tree care page.