Tree and shrub services in Windham, Maine.

Emerald ash borer kills ash trees and hemlock woolly adelgid attacks hemlocks; a quarantine means host material from inside the regulated area cannot be moved freely. Spongy moth caterpillars strip hardwood foliage in outbreak years, and blister rust targets white pine, the tree Windham once floated down the Presumpscot to Falmouth as King's Pines, as the comprehensive plan recounts.

Browntail moth is another concern. The Maine Forest Service says licensed arborists can prune winter webs out of larger trees, and that the webs are removable between October and March. Its hairs cause rashes, so web removal is best done with care rather than by knocking nests to the ground.

Windham's woods are working woods. About 2,940 acres were enrolled in Maine's Tree Growth tax program as of 2014, according to the comprehensive plan, and those parcels carry forestry management plans. Yard trees at the edge of a managed woodlot face the same pests and storms, and a pruning plan for the house lot is easier to follow when it takes the neighboring stand into account.

The plan also notes exemplary natural communities in northern Windham, a Pitch Pine Bog and a Red Maple Swamp, and deer wintering areas in several parts of town. Tree care near those areas keeps disturbance small and favors pruning over removal wherever that is enough.

Timing matters as well. Many deciduous trees are best pruned while dormant, when the branch structure is easy to read, and dead or broken limbs are taken out whenever they appear.