Pruning is an important practice for maintaining the health, appearance and size of flowering shrubs.

Knowing when and how to prune promotes vigorous growth and maximizes floral displays.

Removal of dead, damaged or diseased wood reduces insect- and disease-related problems and allows you to catch problems before they get out of hand.

Keeping the center of the shrub open to sunlight and air circulation improves shrub growth while allowing interior leaves to dry quickly after a rain, which can reduce the incidence of disease.

Removing crossing stems eliminates potential bark damage, reducing the chance of insect and disease problems.

Pruning also forces new growth, which, in most cases, produces the most colorful stems and new flowering wood for future years.

Controlling plant size is low on the list for pruning because it is not a substitute for proper plant selection.

Most plants naturally have beautiful shapes that can be enhanced and somewhat controlled through proper pruning; very few adapt well to shearing.

Most plants stay healthy and attractive longer if allowed to grow naturally. So, reserve the hedge shears for formal hedges.

Removing stems at their point of origin is known as thinning, whereas shortening a stem from the top is heading.

Shearing is simply making a lot of heading cuts.

Thinning cuts are preferable because they open the shrub to sunlight and air circulation.

Heading cuts result in a profusion of growth below the cut, creating a wall of growth on the outside of the shrub that blocks sun from the interior and impedes air circulation.

Formally-sheared hedges should be opened periodically to encourage new growth from inside.

Shrubs with suckering growth habits, such as forsythia and lilac, should periodically have the oldest, biggest stems removed at ground level.

Rejuvenate badly overgrown specimens by removing the biggest, oldest stems at ground level.

This can be done all at once if the shrub is healthy and thriving.

If the shrub is unhealthy, this process can be spread out over a three-year period by removing one-third of the overgrown stems each year.

Keep the sturdiest, well-placed younger stems and remove those that are damaged, spindly or too close to one another.

New suckers will sprout from the roots that will be similarly thinned later in the summer.

Hard pruning should always be done in early spring before the shrub begins to develop new foliage.

It is less stressful for the plant and you can clearly see the stems when they are leafless.

The correct time to prune your flowering shrubs depends on when they flower.

A rough rule of thumb is to prune spring-blooming shrubs soon after they finish flowering because most bloom on “old wood,” which means they set next year’s flower buds shortly after they finish blooming.

Those that bloom in summer and fall usually bloom on “new wood,” which means they set flower buds on the season’s growth and can be pruned in late winter or very early spring.

Like many spring-blooming shrubs, azaleas bloom on old wood.

If you wait too long to prune them, you will remove many of next year’s blooms, especially if you shear your azaleas.

Proper timing and techniques are key to successful pruning.

“Growing Green” is contributed by Diane Dorn, Lehigh County Extension Office Staff, and Master Gardeners. Information: Lehigh County Extension Office, 610-391-9840; Northampton County Extension Office, 610-813-6613