When to prune trees in Western North Carolina, species by species

The short answer

For most trees in the Asheville area, the best time for structural pruning is late winter, roughly mid January through early March. Trees are dormant, their branch structure is easy to see without leaves, and wounds begin to close quickly once spring growth starts.

But there are important exceptions, and a few kinds of pruning should not wait at all. Here is how we think about timing on the jobs we see most often.

Cuts that can happen any time

Safety comes before the calendar. The following work is appropriate in any season:

• Removing dead branches, which are no longer part of the living tree
• Removing broken, hanging or cracked limbs after storms
• Clearance pruning where limbs contact roofs or service drops
• Small corrective cuts on young trees under about an inch in diameter

Oaks: prune in dormancy only

Oak wilt is a fungal disease spread in part by sap beetles attracted to fresh wounds in spring and early summer. It has been confirmed in parts of North Carolina, and the easiest prevention is simply not wounding oaks during the high-risk period.

We schedule oak pruning from November through March and avoid it from April through July. If an oak must be cut in the growing season because of a hazard, we make the cut and move on without delay, and we clean tools between trees.

If you remember only one rule, make it this: no oak pruning from April through July.

Maples, birches and other bleeders

Maples, birches and walnuts bleed sap heavily when pruned in late winter. It looks dramatic but rarely harms the tree. If the sap bothers you, prune these species in early summer after leaves have fully expanded, when bleeding is minimal.

Flowering trees: after bloom

Dogwoods, redbuds, cherries and magnolias set next year's flower buds in summer. Pruning them in winter removes flowers. For these trees we prune right after they finish blooming in spring, keeping cuts light and focused on structure and airflow.

Dogwoods in particular benefit from thinning that improves air movement, which helps reduce anthracnose in our humid valleys.

Pines and other conifers

White pines and other conifers do not respond to heavy pruning the way hardwoods do. Most need little more than deadwood removal and occasional clearance work. Late winter or early spring before new candles extend is ideal. Never cut back into bare wood on a pine, because it will not resprout there.

How much is too much

Regardless of timing, the most common damage we see is over-pruning. On a mature tree we rarely remove more than 10 to 20 percent of live foliage in one year. Young trees tolerate a bit more. Topping, the practice of cutting large limbs back to stubs, is never appropriate and creates years of weak sprouts and decay.

If you are planning work for this winter, autumn is the best time to get on the schedule. Your arborist can walk your trees, mark the limbs and give you a written plan with the right timing for each species.