Now is the time to think about pruning the shrubs and trees in your garden. Pruning in late winter, just before spring growth starts, leaves fresh wounds exposed for only a short length of time before new growth begins the wound sealing process. Another advantage of dormant pruning is that it’s easier to make pruning decisions without leaves obscuring plant branch structure.
Some of the reasons we prune plants are:
- To improve the appearance or health of a plant.
- To control the size of a plant.
- To prevent personal injury or property damage.
- To train young plants.
- To influence fruiting and flowering. Proper pruning of flower buds encourages early vegetative growth.
- To rejuvenate old trees and shrubs. As trees and shrubs mature, their forms may become unattractive.
Types of pruning
Five basis techniques are used for pruning: pinching, heading back, thinning, renewal pruning, and shearing. Some plants require more of one method than another, but good pruning is usually a combination of several methods.
Pinching - is the removal of the terminal portion of a succulent, green shoot before it becomes woody and firm.
Heading back - involves removing the terminal portion of a woody branch by cutting it back to a healthy bud or branch. Heading back will stimulate shoot growth below the cut thus making the plant more dense.
Thinning - is the least conspicuous method of pruning and results in a more open plant without stimulating excessive new growth. Thinning cuts a branch is cut off at its point of origin from the parent stem, to a lateral side branch, to the “Y” of a branch junction, or at ground level. Plants pruned by thinning include crapemyrtle, magnolia, viburnums, spireas, smoketree, and lilac.
Renewal pruning (rejuvenation) - involves removing the oldest branches of a shrub by pruning them near the ground, leaving only the younger, more vigorous branches which may also be cut back. Plants pruned by renewal include abelia, deutzia, forsythia, mockorange, spirea, and weigela.
Types of Tools
Shearing - involves cutting the terminal of most shoots with shearing or hedge clippers. This method should not be used on foundation plants but should be restricted to creating formal hedges.
Use hand pruners to cut stems up to 3/4 inches in diameter. Two types of pruners are available: bypass and anvil. Bypass pruners have sharpened, curved, scissors-type blades that overlap. Anvil pruners have straight upper blades that cut against flat lower plates. Although anvil pruners are usually cheaper, they tend to crush stems as they cut. Furthermore, the width of the anvil can prevent you from reaching in to get a close cut on narrow-angled stems. Due to these drawbacks, bypass pruners are generally recommended.
Use lopping shears to cut through branches that are up to 1 3/4 inches in diameter. Loppers have long handles to give you extra reach and better cutting leverage. For heavy duty pruning jobs, select loppers with ratchet joints or those with gears. Look for loppers with shock-absorbing bumpers between the blades, to lessen arm fatigue. Again, bypass blades are preferable.
Use pruning saws to remove stems you cannot cut with hand pruners or lopping shears. Pruning saws come in many sizes, with either straight or curved blades, and teeth that are either fine or coarse. Use a finely-toothed, curved pruning saw to remove branches up to 2 1/2 inches in diameter. You can make a clean cut with this type of saw where access is difficult. Use a coarsely toothed saw for heavy branches 3 inches or more in diameter.
Use pole pruners to cut out-of-reach branches up to 2 inches in diameter. Pole pruners consist of blades attached to stationary hooks which are mounted on long wooden or aluminum poles. A cord or chain is used to control the cutting action of the spring-loaded blade. Pole pruners are especially valuable on jobs where ladders would be inconvenient or would damage the tree.
Use chain saws to remove branches greater than 3 inches in diameter. Many types and sizes of chain saws are readily available, powered by gasoline or electricity. In selecting a chain saw, carefully consider the tasks for which it will be used. Chain saws should be used only with appropriate safety gear by people who fully understand their operation.
Use hedge clippers or pruning shears to trim thin-stemmed hedges. Manual hedge clippers, and ones powered by gasoline or electricity, are available. All types shear off growth in a straight line, regardless of branch collar or bark ridge location. If you have a long hedge, you may have to use hedge clippers when hand pruning is impractical.
Select quality tools. They will last longer and make pruning more pleasurable. For maximum effectiveness, sharpen blades regularly and dry and oil them after each use. Use a file or whetstone for sharpening hand tools and have an experienced professional sharpen chain saws and power hedge clippers.
Pruning at the proper time can avoid certain disease and physiological problems:
- To avoid oak wilt disease DO NOT prune oaks during April, May, or June. If oaks are wounded or must be pruned during these months, apply wound dressing to mask the odor of freshly cut wood so the beetles that spread oak wilt will not be attracted to the trees.
- To avoid increased likelihood of stem cankers, prune honey locusts when they are still dormant in late winter. If they must be pruned in summer, avoid rainy or humid weather conditions.
- Prune apple trees, including flowering crabapples, mountain ash, hawthorns and shrub cotoneasters in late winter (February-early April). Spring or summer pruning increases chances for infection and spread of the bacterial disease fireblight. Autumn or early winter pruning is more likely to result in drying and die-back at pruning sites.
- Some trees have free-flowing sap that “bleeds” after
late winter or early spring pruning. Though this bleeding causes
little harm, it may still be a source of concern. To prevent bleeding,
you could prune the following trees after their leaves are fully
expanded in late spring or early summer. Never remove more than 1/4 of
the live foliage. Examples include:
- all maples, including box elder
- butternut and walnut
- birch and its relatives, ironwood and blue beech
Additional Resources
University of Minnesota - Pruning Trees and Shrubs
NC State University - Winter Pruning
Michigan State University - Winter Pruning Advatages
Oregan State University - Winter Pruning Temperatures
Rutgers University - Plant and Pest Advisory March 15, 2007
NC State - Pruning Shrubs
