The structure of trees is most evident without leaves on trees. Most certified arborists agree the dormant season is the time to prune trees.
Leafless trees allow arborists easier, faster access. It makes their job more efficient. They can see what they’re doing.
Trees store energy in other tissues once they lose their leaves. Any injury, like a pruning cut, becomes a priority for the stored energy. The plant uses the stored reserves to compartmentalize and close off that injury. During the winter most of the plant’s fuel can be directed at healing pruning cuts.
Dormant season pruning allows more time for wounds to close and harden-off. This is important so wood boring insects can’t easily damage a tree. American elms are usually pruned during the winter months. The insect that transmits Dutch Elm disease can’t enter through a hardened wound.
Apple, mountain ash and pears should also only be pruned when they’re dormant. They are all susceptible to fire-blight. Fire-blight enters trees through open wounds. Winter pruning lets the wound close and reduces the risk of fire-blight infection.
Maple, birch and walnut trees bleed sap when they’re pruned. This makes the cuts on large old trees look really messy. Some studies show the heavy sap run may help the tree heal faster. The studies indicate the sap is a natural wood preservative. So even if it looks bad the sap flow is beneficial.
The only time dormant season pruning may not be a good idea is when a tree has a lot of dead branches. The tree needs all of the live, sound branches it can keep for its own health. Pruning during the growing season assures all of the dead branches get cut out and the live ones stay.
Many trees are neglected. They only get pruned by high wind storms or heavy snows. Studies show well maintained trees withstand storm pruning. These trees are healthier and live longer. Contact a local, certified arborist to prune and maintain your tree investment.