How (and when) to prune trees

Although the traditional time to prune trees is after the leaves fall, I do it as the weather cools. As you make cuts, you can assess what they look like in leaf. On mature trees, remove side branches to make their canopy 6 to 8 feet or higher above the ground. That way you can see under-story plantings, and mowing or walking underneath will be easier. Don't cut the branch collar, a slightly flared area at the base of most branches, about one-quarter to one inch long, depending on branch size, and slightly wider than the rest of the stem. Wounds heal faster when this branch collar is left uncut.

Prune no more than 25 percent of growth, and cut out dead wood. Remove inside and crossing branches. Prune high with pole pruners. Work that requires climbing should be left to professionals.

Don't prune shrubs now. It can stimulate new growth, making them susceptible to winter damage. Never prune wet shrubs and trees; it can help spread disease.

Fall is also a good time to plant deciduous trees and shrubs. Prepare the area by tilling an area 4 to 8 feet wide, or as wide as is practical, adding 20 to 30 percent organic material as you dig. Dig deep enough so the root collar will be slightly above existing ground level. Set root ball on undisturbed or packed soil so it doesn't settle. Don't mulch against the flare or let any soil pile against it more than an inch or two. Remove burlap or wire from the top third of the root ball. Fill the hole, tamping soil firmly in place. Water immediately and thoroughly, and water weekly if there is no rain.

By JOEL M. LERNER, APLD

Special to The Washington Post