Hardwood trees and shrubs without showy flowers need to be pruned in the dormant season to more easily see the structure of the tree, to maximize wound closure in the growing season after pruning, to reduce the chance of transmitting disease and to discourage excessive sap flow from wounds. Recent wounds and the chemical scents they emit can actually attract insects that spread tree disease.
In particular, wounded elm wood is known to attract bark beetles that harbor spores of the Dutch elm disease fungus and open wounds on oaks are known to attract beetles that spread the oak wilt fungus. Take care to prune these trees during the correct time of year to prevent spread of these fatal diseases. Contact your local tree disease specialist to find out when to prune these tree species in your area. Usually, the best time is during the late fall and winter.
