Smart Pruning Pays off

Unfortunately, the science of pruning remains a mystery to most of us. As a result many gardeners either neglect the task of pruning trees and shrubs entirely, or, exhilarated by the first breath of spring, haul out the shears and indiscriminately hack away at everything in the landscape.                      
Of the two options, the first is preferable. Most trees and shrubs will attain their natural size and shape with very little pruning. But proper pruning can do a lot for your landscape:
         
Remove dead, broken, diseased and dying wood. Prune as soon as you detect damage, regardless of the time of year. The most common damage seen after a long winter is breakage, the result of windstorms and the weight of snow and ice on branches.
         
Dieback at the tips of branches is another familiar sight. It can happen after a sudden, hard frost during a prolonged, too-warm autumn, or when a late spring frost occurs after tender, new growth has begun.
          
Left dangling, dead or broken branches can become hazards. They also provide prime points of entry for insect pests and diseases.
         
Prevent trouble. The friction created by rubbing limbs or crossed branches can tear bark and cause serious wounds. The solution is to remove the least desirable of the two limbs rubbing against each other. Remove either the smallest or the least attractive of the two limbs. A V-shaped crotch presents another source of potential trouble; it may split apart during a storm. Either eliminate V-shaped crotches or support them with cables.

Balance the ratio of branches to roots. When you transplant a tree or shrub, you’ll leave many roots behind, no matter how much care you take. To make up for this inevitable root loss, you may need to shorten or thin branches by about a third. Use this as a general rule of thumb, not a necessity.
         
Rejuvenate. Yellow- or red-twigged dogwoods valued for their colored stems are examples of plants that require regular pruning. The new spring growth provides the brightest color. When plants are well established (after three years or so), cut a third of the oldest canes to the ground early each spring before new growth resumes.
         
Forsythia, lilac and weigela also require renewal, but not for the same reason. These shrubs will bloom better and be more shapely and manageable if a third of the oldest wood is cut to the ground at three-year intervals. In the case of lilacs, thinning also helps keep these flowering shrubs free of pests. The oldest wood of lilacs is more susceptible to infestations of borers and scale insects.
           
Maintain or develop desired size and shape. You can minimize the need for pruning by giving trees and shrubs enough space to start with. Before you buy a tree or shrub, check the growth habit and ultimate size to make sure the mature plants will fit the space in your landscape you’ve planned for it.
           
The most beautiful woody plants are those encouraged to develop to their full potential. This is done by providing the right space and then pruning selectively to preserve the natural form. A too-big plant in a too-small spot will always look restricted and uncomfortable, no matter how much pruning is done.
          
The reasons for pruning often dictate the timing. However, most trees and shrubs can be pruned whenever it is convenient for the pruner. Maples and birches are notable exceptions to this rule. They "bleed" profusely from bark wounds when pruned in February and March. If possible, delay all but emergency pruning for them until late spring or early summer. Try not to prune in late summer, as this often stimulates tender growth which can be killed by early fall frosts.
         
Because pruning can be done more quickly and efficiently if there is no foliage to obstruct your vision, early spring before the leaves unfold is a good time to prune most deciduous plants.

For specific information on pruning trees and shrubs, check out these fact sheets on the UNH Cooperative Extension Web site:

• Pruning Deciduous Shrubs in the Landscape
• Pruning Evergreens in the Landscape
• Pruning Shade Trees in the Landscape

By Margaret Hagen, UNH Cooperative Extension Agricultural Resources Educator

For more information call the UNH Cooperative Extension's Family, Home & Garden Center's Info-line (toll free) at 1-877-398-4769 or send us an email. Volunteers are available to answer your questions Monday through Friday 9:00am to 2:00 p.m.

3/9/06