Deciduous flowering shrubs require so little attention that most homeowners don't think about pruning them until they've become an overgrown tangle of stems. Then, pruning becomes an all-afternoon affair. But besides promoting healthy growth and controlling plant size and shape, a few minutes of pruning each year results in a benefit you might not suspect: a big increase in the number of flowers and ornamental fruit — the primary reasons we grow these plants. We're not talking backbreaking labor. "You should be able to keep up with annual maintenance pruning by spending 5 to 10 minutes with each shrub," says Denny Schrock, extension specialist at the University of Illinois at Urbana.
When to Prune
The best time to prune depends on when the shrub forms its flower buds and when those buds open. Flowering shrubs fall into two categories: spring-blooming and summer-blooming.
Spring-flowering shrubs, such as lilac and forsythia, develop flower buds in the summer that will not open until the following year. Prune them immediately after flowering. If you prune too late, you will remove next year's developing buds.
Summer-flowering shrubs, such as rose-of-Sharon and oakleaf hydrangea, develop their buds during the spring growth period and the buds open into flowers that summer. Prune these shrubs during the dormant season — in late winter or early spring before the buds show green.
Before you make any pruning cuts, decide what you want to accomplish. With flowering shrubs, the goal is to enhance the natural form of the plant by selectively pruning branches. When done successfully, maintenance pruning won't be apparent at all.
Remove dead, damaged or diseased branches whenever you notice them. Prune out branches that cross and rub against other branches as well. Always cut back to the ground or to a live bud or branch to prevent further dieback.
Renew and control size
Thin shrubs by cutting branches back to a main branch or stem or by removing the oldest stems on mature shrubs by cutting them back to the ground. The latter encourages strong new stems and flowering. Thinning also helps control shrub height and width and decreases the need for severe pruning.
Many deciduous flowering shrubs, including viburnum, forsythia and beautyberry, respond well when one-quarter to one-third of the oldest stems are removed each year. Doing so completely renews the shrub every three to four years.
After thinning, occasional wayward or overgrown stems may need trimming back, called heading, to enhance the natural shape of the shrub.
Because heading cuts promote branching, it's important to use them prudently. Otherwise, dense growth will develop at the ends of branches and will shade out the rest of the plant, resulting in sparse foliage on the inside. For the same reason, don't head back all the branches to the same length or shear flowering shrubs into globes and boxes. This not only makes them look stemmy, stiff and awkward, but also prevents them from flowering.
Rejuvenate an old shrub
Certain shrubs, even though badly overgrown, can be restored to new vigor by cutting all of the branches back to 4 to 8 in. above ground level. The best time to do this is during the dormant season before new growth starts. The plant will be entering its most vigorous growth period so it will be most resilient.
By summer it will renew itself with healthy, vigorous growth, and within two to three years the shrub will totally fill out. There are a couple of drawbacks to this approach, however. It is usually necessary to thin the regrowth, and flowering could be delayed by as many as three years for some shrubs.
Cut back only those shrubs known to respond well, such as forsythia, honeysuckle and butterfly bush. If in doubt about a particular shrub, consult the local extension service or a good reference book.
Pruning takes courage. But flowering shrubs are forgiving, and they want to grow. As long as you know what you're trying to accomplish with each cut and when you should make the cuts, you can't go wrong.
Prune in winter or early spring
Prune just before flowers fade
Where to Find It
A.M. Leonard, Inc.
241 Fox Dr., Box 816, Dept. TH300
Piqua, OH 45356
Source for Felco, Sandvik and other top-quality pruning tools.
Felco products also available at www.frostproof.com
1540 E. 6th St., Dept. TH300
Corona, CA 92879
Fiskars Lawn & Garden
780 Carolina St., Dept. TH300
Sauk City, WI 53583
J.H. Williams (Bahco) Tool Group
Box 2036, Dept. TH300
Scranton, PA 18501
337-A Figueroa St., Dept. TH300
Wilmington, CA 90744
The American Horticultural Society Pruning & Training
by Christopher Brickell and David Joyce
DK Publishing, Inc.
New York, NY, 1996
Rodale's Successful Organic Gardening Pruning
by Kris Medic
Emmaus, PA, 1995