Principles of Tree Pruning

Protect the Trunk

• Incorrect pruning cuts can damage a tree's trunk or remaining branches, opening the way for disease or weak growth. Every branch has a branch collar, which is a lip of tissue growing around the branch's base where it joins the trunk or parent branch. Do not cut into a branch collar. When removing a large branch, start by making an upward cut part way into the branch's low side about 1 foot from the trunk or parent branch. Cutting a little farther out on the branch removes the branch. Cut off the stub just outside the branch collar.

Prune While Dormant

• Pruning late in the dormant season, winter, reduces the risk of insects or diseases entering the tree and minimizes sap loss and stress on the tree. Prune just before growth starts for the growing season so that the wound is not exposed too long before new tissue starts growing over it. Pruning a deciduous tree in the dormant season also makes it easier to see the tree's form. Exceptions include trees that flower in early spring; they can be pruned just after they flower. Trees that lose large amounts of sap when pruned in early spring will lose less sap if pruned in late spring or early summer.

Do Not Overprune

• Leaving branches on the lowest part of a young tree's trunk for the first few years increases the trunk's strength. After a few years, remove branches from only the lower one-third of the trunk. As the tree grows, remove additional branches until the lowest branch is at the desired height. Never remove more than 25 percent of the tree's total live foliage in one season. Dead branches can be removed any time.

Start Early to Maintain Form

• Pruning should begin the first year after the tree is planted. First, remove all dead, diseased and broken branches. Removing one of any two branches that rub together is the next task. If the tree has two central leaders, or main upright branches, then remove the smaller or weaker one. Pruning also requires cutting back branches that grow beyond the tree's natural form. Remove some branches if doing so is necessary to reduce wind resistance and allow sunlight to reach the tree's center.