A common question gardeners have is when to prune. “When the shears are sharp!” is the often-heard answer. In reality there are a few timing guidelines that do matter.
First of all, certain trees are known to “bleed” when pruned while the sap is rising in late winter and early spring. Maples, dogwoods, birch, elm, walnut and honey locust are the most common.
Bleeding usually won’t hurt the tree, but the pruning cuts are slower to heal which may leave susceptible trees vulnerable to infection. These trees should be pruned right after leaves fall off in autumn.
Cherry trees are at risk from the destructive cherry bark tortrix. The tortrix is attracted to fresh pruning cuts, so cherry trees should not be pruned between May and August when the tortrix is active.
Spring flowering shrubs should be pruned immediately after flowering so that the new growth has time to form next year’s flower buds. Summer flowering shrubs may be pruned in winter because flowers are formed on this season’s growth.
Pruning resources online:
- A guide to pruning trees and shrubs from University of Minnesota Extension
- A Google search of “pruning” limited to .edu sites (Cooperative Extensions links)