HOMEGROWN
Count stems on spring-flowering shrubs
Published: Friday, January 15, 2010 at 3:00 a.m.
Last Modified: Thursday, January 14, 2010 at 4:49 p.m.
It sounds rather heartless to say that we manipulate plants rather than allow them to behave naturally. But that's really what happens when we create a garden. Few of our plants are precisely the same as those that grow in the wild, including many of the natives that we cherish so much.
We leave very little to chance in our gardens.
One of our favorite targets, flowering shrubs, are commonly pruned in winter, a practice that may be convenient for the gardener but risks lessening the spring bloom. Pruning aims to control size but also to promote flowering and a pleasing shape for the rest of the year when foliage becomes prominent.
Because pruning flowering shrubs can be confusing, it helps to follow what I call the one-third rule, keeping in mind that there really aren't any rules at all about pruning. Every three years, beginning the third year after planting, cut one-third of the oldest stems to the ground after flowering. Every year, remove any congested stems at the base to keep the clump as open as possible.
Timing, however, is key. If there really were any pruning rules, one would be to deal with spring-blooming shrubs within 2 weeks after flowering. Because these shrubs develop new growth during late spring and summer, their flower buds are set by the time winter dormancy arrives. Pruning in winter has the disadvantage of cutting off potential flowers.
But most gardeners are in a pruning mind-set in January. Besides, there's a bit of an advantage to pruning spring-flowering shrubs now despite sacrificing the dormant blooms. It's far easier to assess form and reach inside leafless stems. So you may prefer to go ahead and jump into the process.
Next week, we'll talk about pruning another group of shrubs that are more advisedly pruned in winter.
Favorite bloomers
Shrubs that grow slowly may not need pruning until after 5 years of growth. Whenever you begin, remember that you will encourage a more pleasing profile by cutting stems at the base rather than simply shortening them higher up, which nearly always ruins the shape. It helps to keep in mind that where you cut is where the stem will grow.
Flowering quince (Chaenomeles). One of the earliest blooming shrubs, it often begins flowering in January. Take cut branches indoors for a festive display. If stems sprout too far from the base, dig them out and cut off spreading roots.
Deutzia. A favorite of butterflies, clusters of small pink or white blossoms decorate stem tips in spring. To rejuvenate an old or poorly shaped shrub, cut completely to within a few inches of the ground during dormancy.
Forsythia. This exuberant harbinger of spring fills stems with bright yellow blooms. Pruning is usually not needed until plants are 5 years old. As arching stem tips take root and clumps slowly expand over the years, dig out older sections and replace with new ones. Rejuvenate an aged or poorly shaped shrub by cutting to the ground now.
Kerria. This plant may never need anything more than a cleaning out of dead wood, but if too many stems need to be removed, it may be easier to cut them all to the ground. As the clump spreads, dig up and remove unwanted sections. Follow the one-third rule to remove damaged or browned stems and maintain an airy disposition. In winter, the canelike, leafless stems are quite attractive.
Beauty bush (Kolkwitzia). Follow the one-third rule after the plant is about 5 years old. Renew completely by cutting low to the ground now.
Mock orange (Philadelphus). Follow the one-third rule after shrubs are about 5 years old unless growth has been too vigorous by the third year. After spring or summer flowering, stems that have blossomed can be cut back to a lower bud, but to control size, remove a third of the oldest stems. Some cultivars are extremely vigorous and become quite dense. If it becomes impossible to prune out stems, it may be time to lop off the entire shrub low to the ground, which can be done now during dormancy.
Spiraea. For plants that bloom in early spring — commonly known as bridal wreath for their sprays of white flowers flowing along arching branches — thin out a third of the oldest stems annually after bloom. For those that bloom in summer, cut all stems to about 6 inches during dormancy. Summer bloomers can be trimmed for a second, albeit lighter, flowering.
Lilac (Syringa). Probably more problems arise with pruning lilac than any other spring-blooming shrub. Cutting out one-third of the oldest stems at ground level after flowering encourages new shoots to form and restrains unmanageable heights.
Weigela. Removing stems is beneficial only when plant size must be restricted. Cut the entire plant low to the ground during dormancy to renew.
Rosemary McCreary, a Sonoma County gardener, gardening teacher and author, writes the weekly Homegrown column for The Press Democrat. Write to her at P.O. Box 910, Santa Rosa 95402; or send fax to 664-9476.
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