Tree Care Basics: Pruning

Pruning is an important part of maintaining the health and appearance of your tree. Trees, as living organisms, are unique and have different cycles. As such, what may be a good time to prune for one type of tree may put another type of tree at extreme risk for disease? To take out some of the guesswork, we have information sheets entitled “Pruning Trees and Shrubs” and “Pruning Evergreens”, which are very helpful. Knowing why, when, and how to prune will help you in caring for your tree.

Pruning deciduous trees:

The primary reasons to prune are for the health of the tree, appearance, and for safety. Keep in mind that every time you prune, you create a wound on the tree that needs to heal. If your tree has dead or diseased wood, pruning will help the tree heal and recover more quickly. (If you think your tree has a disease, feel free to contact Linder’s so that we can help you determine what would be the best course of action to take.) Additionally, removing branches that cross over or rub against another will help improve the health of the tree.

When pruning for appearance and/or safety, you will need to know when is the best time to prune for your particular tree. As stated earlier, pruning at the wrong time for some trees can greatly increase the risk of disease (or flower loss if your tree is one that flowers). Pruning for appearance includes shaping, thinning, and sucker removal. Pruning for safety reasons includes branch removal for power lines, weak branches that could fall and cause injury, and removal of branches that obscure vision of drivers on streets and driveways.

Making correct pruning cuts are as important as knowing why and when to prune. When removing a sizeable branch, it is recommended that it be completed in several steps to prevent the branch from tearing into the bark of the tree trunk. Do not make the cut flush with the trunk. Instead, locate the branch collar, which is the enlarged area at the base of the branch (see diagram below). You will need to make the final cut just beyond the branch collar leaving it intact. Do not leave any branch stubs, as this will only invite decay.

Step One: Make an undercut at #1, approximately 1/3 to 1/2 way through the branch. This undercut is what will prevent the branch from tearing the bark on the trunk.

Step Two: Make a cut at #2 and cut through the entire branch. The majority of the branch (and weight) is now gone.

Step Three: Make the final cut at #3, leaving the branch collar intact on the trunk. Do not make the final cut flush with the trunk. Do not leave branch stubs.

A frequently asked question is whether or not to use sealer or paint on the tree wound. Studies have shown that using paint or sealant promotes decay. The tree will heal more quickly if allowed to heal unsealed. (The only exception to this is if you must prune elms or oaks during the months that they are most susceptible to disease transmission.) Please feel free to call Linder’s if you have questions about pruning.)

Pruning needled evergreens:

Evergreens generally require little to no pruning, except for removal of diseased, dead or broken branches. Some homeowners choose to shear their evergreens to help maintain a more formal shape. Keep in mind that evergreens tend to grow slowly, so be judicious in the amount you shear/prune. On some evergreens, once you have pruned to the point of seeing branches or bare wood, it may take a long time (if at all) for growth to start.

Evergreens generally put on a flush of growth in spring to early summer. It is during this flush of growth (the new finger like growth is called “candles”) that evergreens can be sheared. If you need to prune your evergreen you can shear off 1/3 to 1/2 of the new candle growth before the new soft candles harden off. If you prune off all of the candles, the evergreen will need to re-sprout from old wood, which will take a long time (if at all).

When pruning out dead or diseased branches from evergreen trees, you will follow the same pruning cut guidelines as outlined for deciduous trees, leaving the branch collar intact on the tree (see diagram and instructions above for pruning).

Do not prune your evergreen in late summer or fall. This late season pruning adds unnecessary stress to the tree as it prepares for winter.

References: University of Minnesota, Extension Service