Pruning improves branch structure, maintains the size and shape, and increases the air circulation and light within the tree, which can improve growth and reduce diseases. Additionally, some young trees may need to be pruned so that they have a central leader (to discourage growing in a Y shape). However, before you begin, make sure that you can prune safely and are confident in how to prune. If needed, contact an arborist for a consultation.

Evergreen trees, like pine and spruce, require little pruning, with the exception of removing dead, broken or diseased branches. Deciduous trees, including fruit trees, do well with winter trims, as do many shrubs. Some species that do well with winter trims include dogwoods, fruit trees, maples, oaks, holly, and other deciduous shrubs. However, before pruning shrubs that bloom in the spring, such as lilacs, forsythia, and azaleas, know that cutting them in the winter will sacrifice their spring blooms for the following growing season. The reason for this is that spring blooming shrubs develop buds in the fall, so you will be removing buds when you prune. If you’d like to avoid that, you can wait and do your pruning cuts a few weeks after they bloom in the spring.

When pruning, there are three important things to remember. First, make cuts just past the branch collar, which is a band of thicker tissue where the branch originates (see photo). Within the branch collar are specialized cells that prevent decay and help the tree to form a scar over the cut. Cutting too close to the main stem and removing the branch collar may lead to decay where the cut was made because these protective cells are removed.

The second principle to follow is to avoid heading back or topping cuts on mature trees. A heading or topping cut is when the branch is cut so that a stub remains. Leaving a stub past the branch collar may result in decay, growth of water sprouts in the following growing season, and unwanted changes to the branch structure. Water sprouts are the fast-growing upright shoots that grow from buds on branches below where they have been cut. (See photo.)

Branch collar on an oak tree.

Lastly, never remove more than 25% of a tree’s growth in a single year. If you have a tree or shrub which has become very overgrown, you will need to have a multi-year plan for pruning to ensure that you do not cut back more than 25% at a time to maintain the health of the plant.

If you are confident in how to prune a tree, start by cutting any branches that have been broken, are dead, or have evidence of disease. Remove branches that cross, as crossing may cause wounds which can become diseased. Before moving on to cutting healthy branches, examine the structure of the plant. You’ll want to make cuts so that branches are spaced evenly around the tree, thinking both vertically and radially. From there, let your pruning goals determine what cuts you make. Your goals may include increasing airflow between fruiting branches, maintaining size, improving blooming or fruiting, or maintaining shape.

One last reminder before you are ready to get out there. When pruning, make sure to sanitize your tools in between individual shrubs or trees, even if there is no evidence of disease. Just like a doctor washing hands between patients, this is just good hygiene and prevents the spread of diseases.

This article is just a short primer on winter pruning, and there is much more information to be found on methods for pruning different species, so please read up on pruning from a reliable source (the Penn State Cooperative Extension website is a great place to start).