Careful Planning, Gradual Pruning Essential for Flowering Trees

As summer approaches, many trees and shrubs are flowering into greenery that highlights any outdoor picnic or barbecue. However, with the flowering of summer comes the challenging responsibility of pruning - an act that is vital to the health of trees and plants and requires more thought than the simple clipping of overgrowth.

"Flowering trees such as the crabapple, dogwood, Japanese maple, and cherry often require more frequent pruning," said Dr. Bruce Fraedrich, vice president of research at Bartlett Tree Laboratories.

Why Prune?

"These trees have a capacity for rapid growth, especially while they are young. They need to be pruned more often because they often grow in a confined space," Fraedrich said. The removal of dead, diseased, or broken branches helps to reduce the amount of stress on a tree and keeps it growing.

The pruning of flowering trees can also help keep the surrounding area safe. Branches that are weak or interfere with things like power lines should be trimmed to avoid possible injury to people or property.

"Before you ever start pruning, you need to know what you want to accomplish and why," Fraedrich said. "Whether the intent is to reduce the tree's size for safety reasons or for health reasons."

Timing is Everything

According to a publication by the Virginia Cooperative Extension, when pruning should take place largely depends on the individual tree, but injury could be inflicted if pruning occurs at the wrong time.

Summer flowering occurs on the new wood produced in the spring, while spring flowering occurs on the wood produced during the summer growth. Pruning for summer flowering plants and trees should take place in the winter or early spring to establish a healthy growing environment for new buds. Pruning for spring flowering plants should take place after the plants have bloomed in early spring. If the tree or shrub is less than two years old, only light pruning is needed.

Other Helpful Hints

Fraedrich warns against overpruning small, flowering trees. "People see the need to reduce them severely, but a homeowner should prune annually and lightly instead of pruning large portions at once. If a tree does become overgrown, the best thing is to reduce size over time instead of trying to solve the problem all at once."

Other pruning practices suggested by the International Society of Arboriculture are to make cuts just outside the branch collar for quick wound closure, avoid leaving stubs, and keep tools sharp and clean.

Avoid Topping

At times, a tree or plant needs to be pruned to avoid interfering with utility lines, buildings, or other aspects of the environment. In these cases, it is important to avoid the practice of topping - the removal of all parts beyond a certain height with no consideration of the plant's structure or health. While many believe topping will reduce a hazard, it actually makes the tree more hazardous in the long run, and it is a temporary and ineffective solution.

Topping "starves" trees because leaves are responsible for creating food. In an act of defense, the tree creates shoots, which grow quickly and are prone to breaking. This can be especially hazardous in windy conditions, seeing as shoots can grow up to 20 feet in one year.

Topping also leaves a tree more susceptible to insects and disease, makes the tree aesthetically unpleasing, and exposes the tree to sunburn, which can lead to cankers, bark splitting, and branch death. It can also cause decay in wounds that cannot close.

The cost of restoring the tree's health is expensive, and topping often produces what Fraedrich calls "high maintenance trees."

Topping Alternatives

Fraedrich recommends reduction pruning as an effective alternative to topping. In this process, the size of longer branches is reduced using cuts back to lateral branches. Some branches can be removed at their point of origin.

Fraedrich also cautions against the "excessive thinning of interior branches." This can lead to excessive growth of upright interior shoots or to limb breakage.

Consulting a Certified Arborist is a good way to learn how to manage flowering trees, especiall if they are large. Knowledgeable arborists will not use topping on flowering trees.

"It can be difficult to know what cuts to make and how to handle a tree's size. Calling an arborist for the first 2 or 3 pruning cycles can really help homeowners learn how to maintain and care for their trees," Fraedrich said.

© International Society of Arboriculture

Contact the ISA-Certified Arborists on staff at the Johnson Tree Company for additional advice.