In the Garden:
Middle South
February, 2011
Regional Report

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3703

These improper pruning cuts, made too far outside the branch collar and ridge, resulted in a stub of dead wood that gives easy access to insects and disease.

Prune with Precision

It has been an extremely cold winter in these parts, with the average temperature nearly five degrees below normal, but the cold season can't last forever. In the next six weeks alone, the daytime average will increase by fifteen degrees or more. Even now, the green tips of some perennials are peeping above the mulch, and the flower buds of early-blooming trees and shrubs are beginning to swell.

There's much to be done, then, in these last weeks before spring arrives, especially in my new garden. When warmth and sunshine prevail, I'll round up late-falling leaves, clear away stubble and dead foliage from last year's perennials, add a fresh layer of compost and mulch to flower beds, and tackle my favorite late-winter chore -- the pruning of woody plants.

Though I consider pruning to be a fairly simple task that is easy to understand and master, the previous owner of my garden made numerous mistakes. Dead stubs remain where branches have been trimmed away, leaving easy entry for insects and disease, and many shrubs have been left to grow unchecked, so that foliage covers windows and creates a safety hazard around paths and driveways.

Since the end of the dormant season (mid February to mid March in the Middle South) is the best time to shape nonflowering plants, as well as those that bloom later on new wood in late summer and autumn, I'll be busy in the next few weeks.

Some trees and shrubs should not be cut back just yet, however. Flowering plants that bloom in spring and early summer, such as redbuds, dogwoods, azaleas, and some hydrangeas and viburnums, have already made flower buds for this year's blooms, so pruning now would remove those flowers. I'll wait to shape these plants immediately after they bloom.

I'll exercise caution with plants that grow in shady conditions, too, as they produce less food through photosynthesis and can be severely weakened by aggressive pruning. As a rule of thumb, I never remove more than a third of their foliage.

Over the years, I've learned three basic principles of plant growth that help me decide where to make a precise pruning cut. First, apical buds (at the tip of a branch) have dominance over lateral buds (on the side of a branch), so the removal of the apical bud results in the growth of lateral buds. When a cut is made just above a bud, that bud will usually become dominant, but if a cut is made mid stem, a flush of growth from a number of buds along the stem may occur.

Also, buds usually grow in the direction they are facing. In general, it is best to prune to an outward facing bud so that new growth is directed up and away from the center of the plant.

Finally, when trimming away larger branches, careful placement of the cut will ensure the production of woundwood, which heals the cut and prevents future insect and disease problems.

To find the proper place to remove a branch or limb, look for the branch collar, a raised band along the underside of the base of the branch. Then locate the branch bark ride, a ridge of bark above the branch, usually parallel to the branch angle. Cut just outside of the branch collar and branch bark ridge for a precise cut that encourages quick healing.

Keeping these principles in mind, begin pruning a tree or shrub by removing all dead and diseased wood, and then eliminating branches that rub together. Also remove the odd green shoot on variegated plants, as well as any shoots growing from below the union of grafted plants, as these branches are extremely vigorous and will eventually outgrow the more decorative branches. Remove branches with winter damage, and eliminate multiple shoots growing from old wounds.

When hedging a row of shrubs, be aware that the part of the shrub that gets the most sun will grow the fastest. Therefore, it's best to trim hedges into an inverted V-shape so they are wider at the bottom, preventing shading and die-back of lower branches and an unattractive "leggy" appearance.

When you've built your confidence with the basics, you may want to try your hand at artful manipulation. Prune small trees with horizontal branches, such as kousa dogwoods and Japanese maples, to enhance their distinct layers of foliage. Or shape an evergreen into topiary, or espalier a fruit tree against a wall.

Possibilities are endless, but proceed with an eye to the future. The more you alter a woody plant from its natural pattern of growth, the more effort you must make to maintain its new form.


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