1 of 2
To rejuvenate overgrown shrubs, head all of the stems back to within 6 to 12 inches from the ground just before spring growth begins. Such drastic pruning will reinvigorate healthy shrubs but should only be performed once or twice a decade.
Photo by Carroll Foster
2 of 2
Buds of spring-flowering plants form on old wood that was produced the previous season. Fall or winter pruning will remove the buds, so prune plants immediately after their flowers fade.
Photo by Carroll Foster
You’ve seen them—shrubs that have fallen victim to the “green meatball” syndrome. That’s what I call it when shrubs are sheared into submission, like little round soldiers in formation.
Each type of shrub, like each person’s hairstyle, looks best when trimmed a certain way. Flowering shrubs in particular suffer from indiscriminate shearing, turning what could be a standout display into just another green blob in the landscape.
To properly prune spring-flowering shrubs, such as azaleas and hydrangeas, you need to understand when and how to prune to maximize their attractiveness and performance.
Knowing when to prune is easy. Spring-blooming plants, defined as those that bloom before June 1, should be pruned immediately after flowering. This is because they bloom on “old wood,” a simple way of saying that their flower buds form in the late summer and fall of the previous year on stems produced that season. Pruning these shrubs in winter would remove flower buds and result in reduced or no spring blooms.
Summer-flowering plants, such as butterfly bush and crape myrtle, which bloom on “new wood,” or current season’s growth, can be pruned in late winter with no effect on blooming.
Knowing how to prune is a bigger challenge. Buzz cuts won’t do, so put away the hedge shears. To prune these plants properly, you’ll need to use hand pruners or loppers—and take your time.
The good news is that these plants usually don’t require heavy pruning, at least not every year. The practice is intended to maintain plant size while encouraging a full and natural-looking outline.
You need to master two types of pruning cuts: thinning and heading.
Thinning cuts remove entire branches down to another branch, to the main trunk, or all the way to the ground. This is the best technique for decreasing the length of leggy branches that extend beyond the outline of the shrub and gently reducing the size of the plant. It also allows better light penetration into the shrub, encouraging more interior branch growth and giving the plant a more layered and full appearance.
Thinning should be your go-to pruning method and can be done year-round. But it will have the least impact on flowering when done just after the plant’s flowers have faded.
Heading cuts should be used less frequently and more cautiously. Heading is a more drastic and less precise pruning method in which stems are cut back indiscriminately. When all of the small branches on the exterior of a plant are headed back, we call it shearing, or hedging, which leads to the “green meatballs.”
While sometimes appropriate for formal boxwood hedges, shearing is not recommended for azaleas, camellias and other flowering shrubs. Heading cuts can be used on flowering plants occasionally, however, to drastically reduce the size of the plants, a process called renewal pruning.
Renewal pruning may be necessary on grossly overgrown shrubs. Not only does it reduce size, but it can also reinvigorate a plant, provided the plant is otherwise healthy. Cut all of the stems back to within 6 to 12 inches from the ground just before growth begins in the spring (mid- to late March). This will, of course, eliminate spring blooms, but you should see considerable new stem growth by midsummer.
Once the new shoots are 8 to 12 inches long, thin them out so only two or three shoots remain on each old stem, then head those shoots to encourage more branching. Make sure your plants are well watered during this process to reduce stress.
Don’t do any additional pruning after August 1, and your reinvigorated shrubs should produce a good flowering display the following spring.
S. Cory Tanner is an area horticulture agent and Master Gardener coordinator for Clemson Extension based in Greenville County. If you have any questions or comments, you can email him here.