Pruning Shrubs

Horticulturist Maureen Gilmer explains how to properly maintain shrubs.

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Shrubs are the structure of this garden, with natural forms providing mass for anchoring perennials. (SHNS photo courtesy Maureen Gilmer)

"It should never look as though it has been pruned." That was the advice my mentor gave. He was a big believer in natural pruning to keep shrubs in bounds. I would learn later through trial and error that he was exactly right--it's pruning mistakes that turn ordinary shrubs into ugly, high-maintenance monsters.

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Natural pruning ensures that flowering shrubs continue to bloom abundantly. (SHNS photo courtesy Maureen Gilmer)

Inevitably, shrubs, whether deciduous or evergreen, grow too large for the space provided. They may crowd walks and gates or encroach onto driveway or parkway. But because they are the backbone of the landscape, they are among the most important of all landscape plants. Longevity can extend their presence for decades, an investment in time that is too valuable to risk destroying with improper pruning.

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Sheared hedges must be pruned often, and cleanup of clippings is time-consuming. (SHNS photo courtesy Maureen Gilmer)

The vast majority of shrubs do not require any pruning at all. They will grow into their natural shapes without any help from you. But when they overgrow to crowd or become a nuisance, you have no choice but to alter their dimensions. However, whipping out the electric hedge clipper is not the magic bullet for this problem. In fact, it can actually increase long-term maintenance.

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In foundation beds, shrubs in their natural form are virtually care-free. (SHNS photo courtesy Maureen Gilmer)

Natural pruning, as I learned, will take you longer to do than shearing, but you'll have to do it so infrequently that it's really the low-maintenance solution.

A shrub that is too tall and blocking the living-room window needs to be resized. If you spread the branches and look inside you'll see the branching structure. This allows you to discern which limbs are supporting that problem-causing top growth. If you cut the limbs deep inside the plant, others will remain on top and will completely cover up the cut point.

Apply this same idea to the sides of any shrub that is growing too wide. Look inside, find out what branches support the straying twigs, and cut them deep inside the plant. In the process you'll you learn a lot about the kind of branching that particular shrub produces. And it shows you the size of twigs that support the new or more desirable growth.

After a natural pruning you should not see any blunt cut ends. You'll also have larger pieces that are easy to gather and carry away. This is preferable to frustrating confetti-like shreds of leaf that inevitably follow shearing. And there is no recovery time with natural pruning because the plant retains its shape--it's just smaller.

Natural pruning also maximizes flowering and fruits. Shearing is an indiscriminate cutter, and it will take off the tips where flowers and fruit are formed. This can eliminate color altogether, rendering a beautiful flowering shrub into a green mass. Plants carefully pruned will retain growth from this year, last year and the year before, which allows for the widest range of flowering wood.

With time, shrubs can show their legs, or the trunk and base of the branches, that support the mass of foliage above. The reason for this exposure is actually lack of exposure. If the foliage head at the top of the shrub is wider than the sides, like a pyramid standing on its point, the twigs and foliage around the bottom are in perpetual shade. The plant will naturally drop these bottom leaves for lack of light. Once they disappear, it is nearly impossible to get them back with some shrubs.

To retain beautiful skirts, always prune the top half slightly narrower than the bottom. Even if it's just an inch or two, that is often enough to ensure adequate exposure to the lowest foliage. Not only does it make the plant appear more natural, the lowest foliage also serves by blocking out light and thus preventing weeds. With exposed legs, it's quite common to develop weed problems in the vacant area beneath the shrub.

Shrubs can be as long-lived as trees, making it vital that you treat them with appropriate care. How much is a big rhododendron worth? When it can't be replaced, it's priceless. Don't sacrifice them to electric hedge clippers and doom yourself to a life of shrub servitude.

(Maureen Gilmer is a horticulturist and host of Weekend Gardening on DIY-Do It Yourself Network. E-mail her at mo@moplants.com. For more information, visit: www.moplants.com or www.DIYNetwork.com. Distributed by Scripps Howard News Service.)

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