Winter (December to early March)
This is the main pruning season. Trees are dormant, you can see the branch structure clearly, and insects and diseases are inactive. It is the safest time to prune oaks and most shade trees.
Spring (March to May)
Avoid heavy pruning while leaves are pushing out, since the tree is spending stored energy. Wait to prune spring bloomers like redbud, dogwood and lilac until right after they flower, or you cut off next year's blooms. Do not prune oaks in this window.
Summer (June to August)
Light pruning and corrective cuts are fine. Summer is a good time to spot dead limbs, since they stand out against green leaves. Avoid big cuts during drought.
Fall (September to November)
Fall is a slower season for pruning since fungi spread spores readily. It is a good time to plan winter work, plant new trees, and have hazard trees checked before ice season.