Reasons for Pruning

Pruning is essential in preserving the integrity and scale of the landscape design. Although this is the primary motive of most homeowners who prune their trees and shrubs, there are other equally important reasons to prune. Regular and correct pruning keeps shrubs and trees healthy and vigorous and prevents potential problems. Properly pruned fruit trees will bear larger crops and ward off diseases better. Carefully pruned flowering shrubs not only blossom profusely year after year, but also remain a desirable size. When a tree is grown in a home landscape rather than in a natural woodland, pruning can guide its branch structure so that when it’s mature, the branches are strong and resist storm damage.

Pruning to Increase Vigor

Regular pruning of shrubs by a technique called gradual renewal pruning can keep a landscape young, vigorous and healthy. Yearly pruning encourages old growth to give way to new wood, which flowers more profusely and is more resistant to disease and insects. Even neglected and overgrown shrubs can be renewed gradually by removing the oldest and tallest branches over several years.

Removing branches also allows the sun to penetrate deep into the interior of the plant. When exposed to sun, foliage expands to its fullest, maximizing photosynthesis — the process whereby plants produce food energy to power their growth. Regular pruning spreads the regrowth and rejuvenation effect throughout the entire plant.

Pruning to Direct Growth

Often newly purchased shade trees bear undesirable and structurally unsound branches that are best removed after planting. Some nurseries encourage side branch growth by cutting back young shade trees to a height of 5 or 6 feet. Although these young trees appear compact and well-proportioned — that’s why they are pruned to this shape — the flourish of lateral and upright branches may be too low to the ground, too close together, or lacking a central trunk. Right after planting is the ideal time to begin developing a better arrangement of branches with minimal pruning.

A tree or shrub can be pruned to fulfill a particular function. Often trees can be trained while young to develop branches that are suitable for climbing or holding a swing. To create a tree for children to climb, begin with a young specimen with a horizontal or wide-spreading habit — for example, apple, crab apple, or pin oak — and prune selectively to promote low branches that spiral radially upward. An appropriate tree for a swing is one with a strong, completely horizontal branch 10 to 20 feet above the ground that has no nearby branches to interfere with the swing’s ropes.

Small-leaved trees, such as thornless honey locust, yellowwood, dogwood, zelkova, or katsura, naturally allow filtered sun to penetrate to plants below. Light levels can be further increased by pruning away lower limbs. Plant trees such as these in a grove to create the low-light setting needed for a shade garden. It is just as easy to create a shade garden beneath more densely foliaged trees — under whose thick canopies grasses and other plants can’t naturally grow — by removing some branches to allow more light to filter to the ground. The trees may need yearly thinning to maintain the desirable light level.

Pruning to Repair Storm Damage

Snowstorms, hurricanes, tornadoes, and thunderstorms can damage even properly pruned trees. Of course, trees that have weak limbs or a poor branching structure are more susceptible to storm damage than ones trained to have sturdy branches and a more open canopy. When severe weather causes tree limbs to snap, the damage can often be repaired and the tree saved with the proper pruning techniques. The techniques are similar to those used for removing large healthy branches.

When severe winds break or damage branches high in a tree, there is little recourse other than to seek professional tree-care help. These branches are often hazardous to remove and may require roping to lower them safely to the ground. After pruning a severely damaged tree, increase its vigor by giving the tree extra care. Consider irrigating, supporting the tree with guy wires, fertilizing, mulching, and controlling pests to help the tree recover.

Pruning to Protect Your Investment

Mature trees make a property more valuable; realtors know that homes with well-kept lawns, large trees, and pleasing ornamental plants sell more quickly and for more money than those not as well landscaped.

A Michigan State University Forestry study concluded that healthy trees can add as much as 15 percent to the value of a half-acre residence. Pruning, which preserves the integrity of a landscape and the health and vigor of plants, is an important way to protect the investment. Each year, as the plants increase in size, the investment in time and care grows. A mature shade tree, which may take 25 years to begin to approach full size and spread, is practically irreplaceable; it could cost several to many thousands of dollars to replace it with a tree of equal size.

On the other hand, neglected trees with dead branches, cavities, or poor shapes can be a liability. Since removing unhealthy trees is costly, taking proper care of plants and pruning them when necessary can reap a financial reward as well as beautify the property.

The dense canopy of a mature shade tree may prevent sun from reaching the ground; this is particularly disastrous for lawn grasses, most varieties of which suffer in more than 65 percent shade. Excessive shade reduces the vigor of grass and makes it fall prey to powdery mildew fungus; eventually it will die. Solve this problem by pruning tree branches or by underplanting the tree with shade-tolerant plants rather than a lawn. Removing some branches permits additional sunlight to filter through to the plants below. On young trees removing a few low-hanging branches is often adequate. However, large shade trees may need repeated thinning for a dense stand of turf to survive or even shade-tolerant ground covers to thrive.