Home / Blogs / ‘Tis the Season (For Pruning Your Trees)!
January 10, 2022
Winter is here, bringing colder and shorter days that drive many of us indoors. Some are already looking forward to the coming spring plantings, be they trees or vegetables, meadows or shrubs. For those who are looking to keep busy outside despite the weather, I encourage you to brave the cold this winter because the season of tree pruning is upon us!
Competing leader recently removed from the top of this Yellow Poplar sapling. The red line indicates where that branch was attached (Photo by Zach Carnegie).
Pruning deciduous trees (those that lose their leaves in the fall) is done for a multitude of reasons. You may find, particularly in young trees planted in open spaces, branches crossing over and interfering with each other. Over time these can rub and wear on each other while swaying in the wind, damaging the bark. Many of our native hardwoods should also be selectively pruned to improve their growth form. This should be done when there are 2 or more leading vertical branches on the main stem or “trunk”. This Yellow Poplar recently had one of the 2 competing leaders removed, as indicated by the red line. This will allow the selected leader to become dominant and in turn, control the overall growth of the tree canopy.
When selecting which of these branches to keep, choose the one with the straightest vertical form and is most in line with the main stem/trunk. Then, eliminate the other competing/interfering leaders. You may also want to eliminate low growing branches to prevent future damage or interference, which was done at the base of this tree. Doing this in the winter allows you to make better pruning decisions since the branches are more clearly defined without leaves obscuring your view.
To be fair, pruning many native species throughout the year is not always a bad thing and in some cases, might be preferred or necessary. For example, pruning some flowering tree/shrub species in the winter may eliminate mature buds and forgo their showy display of flowers in the spring. As well, anytime you notice branches that appear to be dead, damaged, or diseased they should be pruned as soon as possible. In most cases though, the dormant season, preferably late winter, is often the most beneficial time to prune many of our native hardwood species as it helps prevent the introduction of pests and diseases to an otherwise healthy tree.
A prime example can be found in the Oak tree genus (Quercus). There is a fungal disease known as Oak Wilt found across most of the midwest and eastern United States, including parts of the Chesapeake Bay Watershed. This fungus (Bertzeilla fagacearum) enters the tree through wounds in the bark or can be spread through root grafts. This disease is particularly fatal for our native Red Oak group. As the fungus moves into the vascular system of the tree, the Oak responds by walling off neighboring tissues to stop it’s spread, simultaneously blocking the flow of water and nutrients. Red oak species such as Northern Red Oak, Pin Oak, Black Oak, and Willow Oak to name a few, can die within just a few weeks after initial signs of infection. If you wait to prune until mid-late winter, the fungus will not be active, nor will the sap-feeding beetles that carry the spores of this fungus with them as they feed on the sap from tree wounds. The tree can then begin to heal the wound earlier as it comes out of dormancy and renews growth in the spring. For more information about this disease, refer to this USDA Forest Service webpage.
There are several different tools you can use when pruning, depending on the diameter of the branch being pruned. There are hand pruners, loppers, hand saws, pole saws, and chainsaws in various sizes.
Common pruning tools including a gas powered pole saw, loppers, hand pruners, and a hand saw (Photo by Zach Carnegie).
For most DIY pruning, all you’ll need are the hand tools mentioned above. When using a saw, be sure to use the 3-cut method shown below. This helps protect the tree from accidental bark damage which may occur otherwise. The final cut should be made close to the branch collar.
An example of a 3-cut method made using a hand saw on a branch that was low growing (Photo by Zach Carnegie).
As with most things in life, it’s always best to prune in moderation. Try to keep your pruning to less than 25% of the living canopy. Take time to identify the exact species while determining why you plan to prune that tree. This will ensure you make only the necessary, intentional cuts. It’s often better to prune early in the life of a tree so you’re creating the smallest wound necessary, allowing the tree to heal quickly. Pruning of most native hardwood species should be done every 1-2 years for the first 10 years after planting, and at 5 – 7 year intervals after that.
For more information on pruning techniques, refer to the Tree Owner’s Manual from the USDA Forest Service. Always use caution when pruning and be aware of your surroundings. This should include awareness of proximity to powerlines and other infrastructure that a branch may potentially come in contact with. If your tree is growing within a public right-of-way, such as street trees, check with your local regulations before starting. For example, in Maryland a Tree Care Permit must be acquired from the Maryland Department of Natural Resources Forest Service.
MD Forests Projects Coordinator
Forests for the Bay