Gardening Columns

The apple trees in this orchard have been carefully pruned
so they'll produce the maximum amount of fruit.

Pruning Pointers

First published on garden.org on March 2, 2006, by Suzanne DeJohn

It's pruning time in the orchards of Edneyville, an apple-producing region just south of Asheville, North Carolina. At first sight it would appear that these trees grow naturally in their characteristic spreading shape with low-hanging, horizontal branches. But appearances are deceiving: Orchardists methodically prune their trees every winter to encourage that growth pattern.

Prune With a Goal
Pruning is a way of manipulating a plant's growth for a specific purpose. For an apple grower, the goal is maximizing fruit production. In your landscape, you might want to limit a plant's size, promote flowering or fruiting, create a more pleasing shape, rejuvenate an overgrown plant, or remove branches to allow more sunlight to pass through. How you prune will depend on the type of plant and what you are trying to accomplish.

Many gardeners are reluctant to prune, fearing they'll harm their plants. But pruning a plant correctly can improve its vigor and attractiveness. The keys to pruning are having a goal in mind, then doing your homework so you understand the best technique for each type of plant. You should have a reason for every cut you make. Some plants, such as forsythia, are so vigorous you can cut them down to the ground and they'll regrow. But most other plants prefer a lighter touch.

When to Prune
Many woody plants are best pruned in late winter or early spring, just as buds are beginning to swell. The exceptions include spring-blooming shrubs, such as azaleas. These plants set their flower buds during the previous growing season, so pruning them now will remove the flower buds. Instead, prune immediately after flowering, so the plant can produce new growth -- and new buds -- for next year's bloom.

Some plants benefit from a second light pruning in midsummer. Orchardists often prune the young, upright shoots on apple trees, for example, because these branches don't produce fruit. The growers want to limit vigorous vegetative growth and redirect the plant's energy to the fruiting wood. You might want to prune errant branches on a shrub to keep the plant tidy.

In most cases, it's a bad idea to prune in autumn because this encourages new growth that may be damaged by the winter cold. Fall pruning can also interfere with a plant's hardening off process.

Follow the Natural Shape
In general, it's best to prune in a way that follows the plant's natural shape. So, instead of removing the tips from all the branches on a shrub to make a perfect sphere, it's better to cut some branches further back and allow some to remain as they are. As the plant leafs out you can re-evaluate and make further cuts to give it a pleasing form.

Formal hedges, such as boxwood, are often sheared to geometric shapes. However, sheared hedges will form most of their foliage on the branch tips, leaving the interior of the shrub leafless. If you want to reduce the size of the shrub or encourage a more natural shape, you'll have to do it over several seasons, cutting some branches back to the main trunk to allow light to penetrate and to encourage its natural growth pattern.

Here are a few pruning guidelines:
1. All plants benefit from having diseased, broken, damaged, and rubbing branches removed, and this can be done at any time of year.

2. Prune back to another branch or outward-facing bud.

3. When cutting large branches, cut halfway through from the top, then make a cut underneath, then finish the cut from the top. The bottom cut prevents the bark from stripping when the branch falls.

4. A rule of thumb is to remove no more than one third of the growth in any one season. If you need to remove more, wait a year to avoid stressing the plant too much.

5. Use sharp tools for clean cuts.

6. Avoid sealers unless there is a specific reason to use one, such as to minimize attack by borers. In general, pruning cuts heal faster when left unsealed.

7. Walk around the plant as you prune, to keep the plant reasonably symmetrical.

8. Stay safe. If you're not up to a big pruning job, hire a professional.

I love driving by the orchards and seeing all the pruned branches on the ground; it's a signal that warm weather is just around the corner. So take your cue from the apple growers and head out to prune on a sunny, early spring day.