Not knowing why to cut, when to cut or where to cut can make pruning one of the most terrifying maintenance jobs in the home landscape.
The first cut can be the scariest, as it is for the child climbing into the barber's chair for the first time. All pruning is potentially harmful because each cut creates a wound that takes energy to close and can provide entry for insects and diseases.
But like a good haircut, a good pruning job can rejuvenate and restore. (Just ask anyone who has brought an unruly lilac under control.)
Pruning is surgery performed to remove broken, hazardous or dead limbs and branches, to control a plant's size and shape, to maintain its natural beauty or to improve flowers or fruits.
"Pruning does injure the tree," says Dennis L. Patton, horticulture agent for the Johnson County, Kan., Extension Office. "But it is also a renewal process."
Spring-flowering trees and shrubs -- flowering dogwood, redbuds, lilacs, Bradford pears, crab apples, forsythia and spirea among them -- should be pruned soon after they bloom.
They bloom on the previous year's wood and will set their buds for next season as early as late summer. If you wait until then or later to prune, you will be cutting off next year's bloom.
Summer-flowering trees, on the other hand, bloom on the same year's wood and should be pruned in early spring or during the winter to maximize bloom power.
Too often homeowners reach for the wrong-sized pruning tool for the job. Patton offers these "rules of thumb." Use hand shears to cut branches the size of a little finger or smaller. Twisting shears to cut larger branches will strain and weaken them. Use loppers for branches smaller than your thumb, or anything up to 1 inch in diameter.
For larger branches, use a pruning saw.
Trees. One of the first times a tree should be pruned is when you plant it.
Thinning out branches on young trees helps eliminate weak crotches and crossed branches, and it prevents bad branch angles from forming.
Pruning a mature tree corrects other problems. In older trees, for instance, leaves grow heavy at the tips of the branches. Thinning out some of that growth results in better light and air circulation at the center of the tree, which stimulates growth and prevents die back. It also creates a more open canopy that lets strong winds blow through the tree's crown more freely, with less likelihood of damage.
Shrubs. There are three methods of pruning shrubs: thinning, heading back and rejuvenating. Thinning involves cutting off twigs or side branches where they attach to the main stem.
Heading back is a more selective process of cutting the terminal part of a branch back to a bud or another branch, especially useful on leggy shrubs because it stimulates growth of smaller buds and shoots lower on the stem, resulting in thicker growth.
Rejuvenation is the most severe pruning job. It can be used in varying degrees on older plants that have become too big or don't flower well anymore. On multiple-stem shrubs, such as spirea, forsythia and japonica, rejuvenating calls for cutting back all the stems to 3- to 5-inch stubs, especially if the shrub has become too large with too many branches.
Lilacs in particular take well to rejuvenating cuts. One of the best ways to keep them flowering is to remove about a third of the branches -- all the way to the ground -- each year over a three-year period.