Many pruning jobs can be avoided by selecting plants with characteristics appropriate for the site in terms of growth rate and ultimate size. Logic and reason also apply. For example, a white oak should not be planted directly beneath utility lines. As the tree grows and interferes with the lines, the tree will be pruned. This completely destroys the natural character of the tree and often leads to its early decline. The same is true when choosing a tree for a planter or other limited space. Small or intermediate-size trees should be considered. Good choices would include Crape Myrtle, Foster Holly, Redbud or Japanese Maple.
Deciduous plants should be pruned during winter when plants are dormant and not actively growing. Spring-flowering trees and shrubs, such as forsythia, azalea, flowering quince and dogwood should be pruned after they bloom. Deciduous summer-flowering trees and shrubs, like crape myrtle and glossy abelia, should be pruned during the dormant winter season before spring growth. Crape myrtle can be forced to form two or three complete flushes of bloom during the growing season by removing the seed clusters when the blossoms fade.
Conifers (needle evergreens) are best pruned during the candle stage (when the young vigorous growth is 2 to 6 inches in length). Conifers will not tolerate severe pruning and will likely decline or take on a mishappened appearance when cut back to older wood. Many broadleaf evergreens, including dwarf Japanese hollies, Chinese hollies, wax-leaf ligustrum and boxwood can be sheared during the growing season to maintain a desired formal shape.
Frequency of pruning depends on vigor of growth and desired formal shape. Overgrown shrubs can be renewed by pruning them to within 8 to 12 inches of ground level, but timing is critical. Renewal pruning of overgrown shrubs should be done from mid-January through early April. Late fall renewal pruning could induce a new growth flush and make the plant more susceptible to winter injury.
In the past, BB trees have been pruned at transplanting time, but this practice has been amended. The traditional rationale was that reducing the top by 25 to 40 percent compensated for root loss and would result in better tree survival. Pruning should be done to remove damaged branches and to improve the structure of the plant. Overlapping, parallel, and crowded branches should be pruned after installation. Cosmetic pruning to improve the form and shape of the plant is also recommended.
Shade trees require pruning for the same reasons as other landscape plants: to prevent branches from rubbing against each other; to remove broken or damaged branches and to eliminate double leaders or narrow v-shaped crotches.
Good Pruning Practices
The basic principles of pruning apply to trees. A branch should be cut back to a lateral side branch or bud or to live, healthy wood. The cut should be made at a slant next to a bud that can produce new growth. "Thinning out" is a term used to describe removing an entire branch at its point of origin. This procedure results in a more open tree and is the least conspicuous of pruning practices. This also conforms to the normal branching habit of the tree. "Narrow" crotched limbs should be removed, as they are the weaker branches of a tree.
"Flushcut and paint" has been the standard recommendation for pruning trees for more than a century. However, recent research by the United States Forest Service Northeastern Forest Experiment Station has shown that this practice may work against nature's design and the tree's best interest. At the base of every branch is a collar that contains a chemical zone which inhibits the spread of decay in the trunk. When decay develops in a branch, it moves down the branch until it reaches the protective chemical zone. Once there, it stops and a callus forms after the branch falls off. If the collar of the branch is removed during pruning, the chances of the trunk becoming infected by decay and canker-causing microorganisms are greatly increased. Pruning cuts should be made just outside the branch collar, not flush with the trunk. The branch collar is the swollen area at the base of the branch that sometimes has a bark ridge.
In the past, part of the standard recommendation has been to apply a generous coating of an approved tree wound dressing to all fresh cuts. It was believed this would prevent decay-causing infection. Research has proven that all of the wound dressings currently available do nothing to prevent decay, and some actually serve as a food source for microorganisms.
New materials to prevent infection are now being tested, but they are not yet on the market. A light coating of a wound dressing might be used for cosmetic purposes.
Pruning Schedule
Tree-pruning does not have to be limited to fall or winter, although these are good times to prune as the tree is dormant. Spring-flowering trees should be pruned immediately after blooming. Summer flowering trees could be pruned before new growth begins in the spring.
Maple, birch, dogwood, and elms are known as "bleeders." When these species are pruned in late winter or early spring, the wounds bleed. This flow of sap is more unsightly than damaging to the tree. Pruning these trees could be delayed to midsummer which is a good time to judge whether trees need pruning or thinning. The one time when trees should not be pruned is during early spring when buds are breaking and during leaf expansion.
Pruning Tools
There are specific tree pruning tools that should be used for the various size branches and pruning jobs. The smallest branches and twigs (1/2 to 3/4 inch in diameter) can be pruned with hand shears. The anvil-type pruners are satisfactory, but the scissors-action pruner is recommended for close-cut precision pruning. For branches limbs of 3/4 to 2 inches in diameter, lopping shears are used. For larger branches a pruning saw is necessary. These narrow-bladed curved saws with coarse teeth are designed to cut smoothly and cleanly. Pole pruners with telescopic handles can be used from the ground. Chain saws can be used on the largest of branches.
Whenever climbing is necessary, it is imperative to use ladders, ropes or pulleys. No one must be allowed in the tree with climbing spurs unless the tree is to be taken down. The use of spurs damages trees and is regarded as an unprofessional practice.
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