Trees are pruned for health, safety, and appearance reasons. Two important aspects of pruning are timing and technique.
February through March is generally regarded as the best time to prune most deciduous trees. The absence of foliage at this time of year gives the individual a clear view of the tree and allows the selection and removal of appropriate branches. Also, the walling-off or compartmentalization of wounds occurs most rapidly just prior to the onset of growth in spring. Oaks are an exception. The winter months – December, January, and February – are the best time to prune oak trees.
Deciduous trees can be pruned at other times of the year with little or no negative consequences. However, if possible, avoid pruning deciduous trees in spring when trees are leafing out and in fall when trees are dropping their leaves.
To reduce the risk of an oak wilt infection, do not prune oaks from March through October. Oak wilt is a fungal disease that is lethal to many oaks. It can be spread from infected trees to healthy trees by sap-feeding beetles ("picnic bugs"). If an oak tree must be pruned in spring or summer (such as after a storm), apply latex house paint to the pruning cuts to avoid attracting sap-feeding beetles to the wounds.
Proper pruning techniques
When pruning trees, make the final cut just beyond the branch collar and branch bark ridge. The branch collar is the swollen area at the base of the branch. The branch bark ridge is the dark, rough bark ridge that separates the branch from the main branch or trunk. Pruning just beyond the branch collar and branch bark ridge retains the tree's natural defense mechanisms and promotes compartmentalization and callus formation.
To prevent extensive bark damage, use a 3-cut procedure when pruning branches that are greater than 1½ inches in diameter. Make the first cut 6 to 12 inches from the main branch or trunk. Cut upward and go about one-third of the way through the branch. Make the second cut 1 to 2 inches beyond the first. Saw downward from the top of the branch. As the second cut is made, the weight of the branch will cause it to break at the pivot point between the two cuts. (The initial, bottom cut prevents the branch from ripping off a large piece of bark as it breaks.) Make the final cut just beyond the branch collar and branch bark ridge.
The final cut of the three-cut procedure is made just beyond the branch collar and the branch bark ridge.