Growings On: When to prune landscape plants

Published 8:00 am Thursday, May 12, 2022

Traveling through nearly any residential neighborhood will reveal landscapes that are well cared for. Ornamental trees and bushes can be a most attractive addition. Unfortunately, without proper care, they may also become a distraction.

Ornamental plants in the home landscape are pruned for many reasons.

Some plants are pruned routinely to maintain a desired size or shape. Others are pruned to promote healthy vigorous growth, flowering or fruiting. Sometimes it is necessary to prune shrubs that overgrow their sites, crowd other plants or limit the view from windows. Plants damaged by insects, diseases or freezing injury may require corrective pruning.

Each plant in the landscape has its own growth habit and a different requirement for pruning. Some shrubs have dwarf growth habits and may never require pruning, while vigorous large-growing shrubs may require frequent pruning.

With diverse growth habits and varying pruning requirements it can be overwhelming to try to figure out when and how to prune each variety.

Not pruning correctly, or at the wrong time, can lead plants to become irregular in shape, more vulnerable to cold damage or pests, or less likely to flower at their full potential.

By understanding the importance of timing and using correct pruning cuts you can prune woody ornamentals with confidence.

With flowering ornamentals setting buds at various times of the year, it can be confusing to know the best time to prune. Try remembering the May rule: If the plant blooms before May, prune after flowering; if the plant blooms after May, prune just before spring growth occurs (February–early March).

A lot of our flowering ornamentals, such as forsythia and azaleas, set their flower buds in the fall.

Pruning these woody plants in the winter would remove these buds and severely limit the flowers available come spring. Summer flowering ornamentals, such as abelia and chaste tree, set flower buds on new spring growth and will not be affected by winter pruning.

As with everything, there are some exceptions to this rule.

Oakleaf hydrangea, which sets its flower buds the season prior, as well as late-flowering azaleas, which bloom in May, June or July, should be pruned after they flower.

Woody plants grown more for their foliage, not flowers, can be pruned anytime during the winter, spring or summer months.

When pruning it is important to remember that wherever the plant is cut, regrowth will be stimulated, generally happening within six to eight inches of the cut. The harsher the pruning, the more regrowth you will have.

There are two basic types of pruning cuts: heading and thinning.

Each cut generates a different response within the plant and should therefore be used for specific occasions in the landscape.

A heading cut is the most invigorating, as it encourages regrowth near the cut. As a result, the plant will become more compact in shape and will lose its natural form.

Conversely, thinning cuts remove an entire limb or branch back to another branch, bud or the trunk. This cut is the least invigorating, as new growth will occur on the untouched limbs and/or branches.

This cut allows the plant to stay in a more natural shape and leads to a fuller looking plant.

If branches are larger than two inches in diameter, make sure to use the three-cut sequence to avoid damaging the plant — the first cut should be about one foot out from the trunk and one-quarter to one-half of the way through the underside of the branch, the second cut should be a few inches away from the first cut one-quarter to one-half of the way through the upper side of the branch, and the third cut should remove the branch just outside the branch collar.

Pruning is an essential management task if you want strong, healthy plants and an attractive landscape.

To be successful in your pruning endeavors, make sure you understand appropriate pruning times (remember the May rule), use the correct pruning cuts for the task at hand (heading vs. thinning cuts), and work with the right tools for the job.

Additional detail about pruning trees and shrubs can be found in University of Georgia Extension Bulletin 961: “Pruning Ornamental Plants in the Landscape.”