Trimming oak trees as part of a standard routine of tree care will help improve their health and appearance. In addition, trimming oak trees can help protect people and property by removing dead branches, branches that overhang buildings or walkways and any that could be knocked down by stormy weather.
Like most large trees, oak trees should be pruned during their yearly dormant period, according to the University of Illinois Extension. The dormant period typically lasts from late November until February, though it may be slightly longer in colder climates. Trimming oak trees near the end of the dormant season also shortens the amount of time that open "wounds" from the removed branches are left on the tree before the new growing season allows the tree to heal the areas where it has been cut.
Oak trees should never be trimmed between April and September, since trimming during the growing season makes the tree more vulnerable to infestation by pests and diseases, especially oak wilt. Oak wilt is especially dangerous to oak trees during the growing season because it creates blocks in the tree's vascular system, preventing the tree from drawing food and water into its branches. Dead branches, however, may be removed at any time during the growing season without risking the tree's health.
In addition to being trimmed at the proper time during the year, oak trees should also be trimmed at the appropriate times during their life cycles. Trimming young trees helps maintain their shape as they grow. On young trees, branches that cross one another or that point back toward the center of the tree should be removed. Removing the lowest branches can help raise the crown of the tree if desired. The "leader," or main branch, on a young oak tree should never be trimmed. Any dead branches on young trees should be removed as soon as possible to protect the tree's health and to prevent dead branches from injuring family members, property, or pets.
With these tips for trimming oaks, you will maintain healthy, safe trees in your yard.