Mature trees that haven’t been trimmed in more than 4 years might be vulnerable to broken branches. This is especially true for ash and maple trees. When we address a trim on mature deciduous trees, it’s really the lateral branches or ones that are parallel to the ground, that need to be thinned especially. These are the one’s that tend to break under the weight of snow or ice.
Branches breaking under the weight of snow, can have several negative consequences. First, when a tree branch breaks it can damage patio fixtures, windows, gutters and nearby vehicles. Secondly, the nature of the break can damage the tree’s appearance. Finally it can influence long-term health.
A fresh and uneven break can serve as an entry point for tree diseases and harmful insects the next spring. While trees can be repaired by cabling and bracing broken branches back in place, it’s ideal to just keep the tree trimmed in the first place.
Winter is actually the ideal time to prune most trees as they will be in dormancy and any loss of potential energy capture due to lost canopy is minimized since the tree is not growing during winter.
Some species of trees should only be trimmed in winter for a different reason. They are prone to certain airborn disease which are not present while the tree is dormant. For the same reason that a snow broken branch can act as an entry point for disease and insects, trimming the following species of tree during the growing season can make it vulnerable to species specific disease. Blight is the most common example (a disease of crab apple and other flowering ornamentals)
ArborScape’s arborist policy procedures dictate that we will only trim the following trees in winter.
We schedule these in January and February.
So cottonwood, ash, maple, and other large deciduous trees, we recommend trimming now if they are overgrown and prone to winter breakage. If you have a crab apple or elm, make sure to schedule it in winter as that’s the only time that a certified arborist will perform work on them.
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