It’s easy to assume that trees are a “set it and forget it”-type plant. After all, trees seem to grow just fine—without human intervention—all the time. But the trees in our yard, near our business, or in our local parks actually need regular trimming and maintenance in order to remain healthy and strong over time. What you may not know is that there are distinct periods of the year that are better “trimming times” than others. For most types of trees, the ideal pruning period is late winter—though there are a few exceptions.
In climates like ours, deciduous trees drop their leaves in the fall in preparation for a dormant period during cold winter months. Think of dormancy like a deep sleep or hibernation. During dormancy, a tree stops growing and dramatically lowers its metabolism and energy consumption to wait out the winter. Once spring has sprung, the tree “wakes up,” resumes normal metabolic functions, and begins to grow once again. This dormant period is the perfect time to trim or prune healthy branches, for a handful of good reasons.
Most importantly, trimming during dormancy is easier on the tree. The wounds created by trimming actually heal faster during cold winter months than they would during the growing season—this is because the tree is not in “grow mode,” when energy would be diverted from healing and spent on putting out new shoots instead. There is also far less insect activity and airborne fungi during the winter, which means less chance of an infection or infestation at the trim site.
Also important: Trimming during dormancy is easier on the person doing the work. It’s far easier to see what you’re doing without all the leaves obscuring your view, which means it’s less likely that you’ll accidentally cut the wrong limb or prune at the wrong place. Dormant trees have lighter branches, which makes for less dangerous maneuvering, and they also produce less sap—though that’s less a safety or tree-health issue, and more a matter of convenience (any tree service provider or outdoor enthusiast understands the pain of removing sap from tools and clothing).
What happens when you trim healthy branches when they’re not dormant, you may ask? The result is usually major tree stress. It’s important to know that trimming a branch is a surefire way to encourage fast new growth. Therefore, trees trimmed during peak summer suddenly find themselves with extra growing to do in high temperatures, adding unnecessary stress to the tree’s natural metabolic functions. Healthy branches trimmed during the autumn are triggered to grow too late in the season, which may prevent dormancy altogether and shorten the lifespan of the tree.
As mentioned above, there are a few exceptions to the dormancy-trimming rule. First to note would be in cases where dead, dying, or diseased branches pose a threat to nearby structures or people. Healthy branches should be pruned during winter months; unhealthy branches should be pruned ASAP before they become a dangerous problem, no matter the time of year. This is especially true in Minnesota, where fall storms and winter snows can cause serious stress on tree limbs and often lead to fallen branches.
Another exception would be those trees and large shrubs that bloom in the early spring months, like lilac or magnolia. These types of flowering trees should be trimmed right after they finish flowering in spring—this ensures the best possible bloom for the following year.
Trimming a tree, especially large or high-up branches, is a dangerous undertaking and is best left to the professionals. An experienced tree service provider knows when, how, and where to trim your tree to encourage healthy growth, reduce potential damage, and promote vitality for years to come.