Most trees, with the exception of maple trees and some flowering ornamental trees, are best trimmed in the early spring or late winter before the branches start budding. If you trim your tree later than this, it may not look as good throughout the coming year. But why? Here's a look at how late trimming affects your tree.
The tree has to put a lot of resources into producing buds, which later become leaves. Plus, it does this in the springtime, after it has been sitting dormant all winter and not producing a lot of food. Thus, budding can be hard on the tree; it's a demanding process.
If you let the tree bud and then trim away a bunch of its budding branches, then it has wasted effort and resources producing those buds, only for them to be removed. What is more, it will have fewer leaves in the coming season, so it will be less able to produce more food for itself to make up for the resources it lost making buds. Although this won't usually claim the tree's life in one season, if you prune late several years in the row, the tree may slowly die back and wither away.
The other main issue with late trimming is disease. Once the weather warms up, all of the fungi, insects, and bacteria that cause tree diseases become more active.
If your tree was only trimmed a couple of weeks before they show up, the tree will still have some open wounds with sap leaking out. The fungi, insects, and bacteria will be attracted to these wounds and more likely to infect your tree.
This is particularly a problem with oak wilt, a deadly infection that affects oak trees. The fungi that cause oak wilt are spread by insects, which simply love open wounds on oak trees. Oak wilt claims a tree's life within a year or two.
If you trim the tree early enough in the spring, the wounds will be mostly healed by the time pathogens become active, so your tree is less likely to become infected.
If the tree has begun to bud, it's too late in the season to safely trim that tree. Remove any dangerous branches, but otherwise, let the tree sit until next season. Most trees will be better off skipping a year of pruning than being pruned too late in the spring. For more information, contact a tree trimming service.