Pruning pointers: Trees, shrubs benefit from an occasional trim

It you have shrubs or trees on your property, a little pruning skill is a terrific asset.

You can save money, your plants will be healthier and look better, and it can give you a feeling of satisfaction in a job well done.

Katrina Lewin, a horticulturist at The Morton Arboretum in Lisle, Ill., spends much of her time pruning: 50 percent of her workday during the winter, she says.

There are some basics that every gardener or homeowner should know. Lewin explained them as she applied her skills to a witch hazel that needed some work.

Tools of the trade

Lewin relies mostly on three items: a long-handled lopper, a hand pruner and a folding hand saw. The first two should have bypass blades (operating like scissors) that should be sharpened once a year or so, depending on use. The lopper requires both of your hands; the hand pruners (or shears) need just one hand. The folding hand saw, such as Felco's F-600 (we found one on Amazon.com for $30), looks small but is a workhorse.

For trees, you're usually looking to create a dominant, central leader — a main stem growing straight up to define the vertical structure — that will result in a stronger tree. For shrubs, you want to create a more pleasing shape and/or to spread out the branches to create a better air flow for the plant.

For trees, winter and late fall are the best time; Lewin likes to be done by late March. "You don't want to prune when insects are active; you don't want to create wounds that will attract them," she says.

For shrubs, "it depends on when they flower," she says. "Spring-flowering shrubs (should be pruned) right after they flower (and before) they'll be setting their buds for the next spring. Summer-flowering shrubs can be pruned in the fall or winter dormant season."

Lewin generally has a set of steps or priorities. For trees or shrubs, the first step is to cut away dead or damaged branches, then thin out congested areas. With trees, next go for any branches that compete with the central leader. For a shrub, take out crossing branches and do some shaping for symmetry.

Take your time, especially with trees. A shrub sends up shoots from the ground all the time, but trees are more permanent. If you botch the job and make a bad cut at that central leader, it will be obvious you botched the job.

For tree branches, cut just beyond the branch collar — the natural swelling an inch or two away from the main leader; do not cut flush to the tree. On a branch, cut at a branch union, not mid-branch — "otherwise you'll have a stub that will just die," Lewin says.

The Morton Arboretum tries to prune each tree every year. Young trees get a lighter trim, and no tree should have more than 20 percent of its live branches trimmed in a year.

For shrubs, Lewin says, "you can be very aggressive. There are some that can tolerate being cut to the ground and they'll come back." Also, if you're working on a shrub and thin or cut the foliage at the bottom, leave some in case something happens to the older branches higher up.

This story was originally published October 29, 2011 at 12:00 AM with the headline "Pruning pointers: Trees, shrubs benefit from an occasional trim."