Jessica Carlson

Otter Tail County Master Gardener

According to the University of Minnesota Extension, the best period for most pruning is from late winter to early spring.  During this dormant time, it reduces stress, minimizes disease spread, and makes it easier to see the structure of trees and shrubs.

Using the right tools makes pruning easier and safer. Most tasks require pruning shears, which cut branches up to 3/4 inches thick. Lopping shears handle branches up to 1 1/2 inches with their longer handles for extra leverage. Hand saws are essential for branches over 1 inch, and varieties like tri-cut or razor tooth saws can easily cut through limbs up to 4 inches in diameter. 

When pruning trees, remove dead, diseased, and crossing branches, as well as water sprouts and suckers.  On younger trees ensure there is only one main leader by trimming out any other competing leaders. Pruning improves tree shape, flowering, and air circulation. For apple trees and similar fruiting varieties, trim to allow sunlight to reach fruit spurs. Annually, prune up to 25 percent of the canopy on middle-aged trees and about 10 percent on older ones, spreading heavy cuts over several years to prevent stress.

To shorten a branch or twig, cut 1/4 inch above an outward-facing bud to guide new growth. For large branches, use the three-cut method: make an undercut 6–10 inches from the trunk about 1/3 through, then an overcut a few inches further out to remove most of the weight, and finish with a final cut just outside the branch collar to remove the stub. A circular wound shows a proper cut, while an oval wound shows collar damage and a potential for decay.

Oak trees require special care in Minnesota. Avoid pruning oaks from April to October, as cuts attract sap beetles that spread the deadly oak wilt fungus. Prune only during the dormant season to reduce infection risk. If branches are damaged during restricted months, cover cuts with latex paint or wound dressing to deter beetles.

Coniferous trees generally require little pruning if planted in sufficient space. Remove new growth buds (“candles”) to prevent further growth. Branches typically do not regrow once cut, so remove them carefully. When pruning lower branches, ensure at least 75 percent of the tree stays as live tissue, since evergreens rely on lower branches for chlorophyll.

Shrub pruning encourages flowering or fruiting but try to avoid trimming for size by planting shrubs where they fit at their mature size. Prune most shrubs in late winter or early spring while dormant which promotes growth and wound healing. For spring-blooming shrubs, prune right after flowers fade.

After pruning, clean your tools by wiping off sap or debris and disinfecting blades with rubbing alcohol or diluted bleach. Once dry, oil the blades to prevent rust and keep them operating smoothly. Regular sharpening ensures easier future pruning and cleaner cuts.

Some pruning tasks, like handling large trees or removing significant branches, should be left to professionals. Pruning combines science and art, so while it takes time to master, and in my case a few mistakes made, it is a skill anyone can learn.