MASTER GARDENER: It’s time to prune
We're all anxious to see how our landscape plants are going to survive this cold winter we're having here in Aiken; a friend in Woodside had a dependable reading of 11.2 degrees at sunrise on Jan. 7. We are in Zone 8A according to the 2012 USDA plant hardiness map, meaning that our average annual minimum winter temperature is between 10 and 15 degrees Fahrenheit, so you can see that we're at the lower end of our average this year. According to the local Gardening Almanac for Aiken and Vicinity, we will still have a 50 percent chance of frost on March 26, so we have about a two-month wait for spring. So what is a gardener to do while waiting impatiently for spring? There are many tasks that will keep us busy until the weather warms up, and one of the most important and rewarding is pruning.
It's much more effective to demonstrate pruning than to describe it. But I will share a few “rules of thumb” with you here, and encourage you to consider pruning your own landscape plants. We will limit this discussion to pruning shrubs because you can reach them safely and I hope you can find one in your yard to “practice” on if you are inexperienced. You will need three basic pruning tools: a hand pruner for branches that are under a half-inch diameter, a lopper for cuts up to an inch and a half, and a saw for thicker branches.
A properly pruned shrub can be a work of art and does not look as if it has been pruned. Pruning cuts should be hidden inside the plant where they will be covered by remaining leaves. When pruning, you should remove only about a third of a shrub's healthy branches at a time. The first step in pruning a shrub is to remove all dead, diseased or injured branches. Remove branches that cross or touch each other and those that look out of place. Then use either the shearing (heading back), thinning or renewal pruning techniques.
Shearing: The practice of shearing a shrub is most often accomplished with a hedge trimmer that produces uniform shapes in our landscapes (think ice cubes or meatballs) that appear formal to the eye. You should make the cuts about 3 to 6 inches below the desired height because the pruning will encourage a new flush of growth that will bring it up to its desired height. This new flush of growth creates a dense layer of outer foliage that shades the interior of the shrub, and this is how a shrub with an abundance of outer growth and a dead-looking center is created. Over the years it becomes increasingly troublesome to prune sheared shrubs because removing even the recommended third of their growth produces an unsightly result (no leaves, just bare branches).
Thinning: The thinning technique for pruning shrubs is often preferred over shearing. If the shrub is still too dense or large after removing dead and/or crossed branches, cut back some of the oldest branches (those with the largest diameter) from the shrub's interior at several different heights. This practice will allow light to reach the shrub's center and will result in growth in the interior of the shrub. Varying the cutting height of those interior branches will result in a more natural appearance of the shrub, and using the thinning technique ultimately results in healthier shrubs. When light gets into a shrub you will have better air flow through it and the shrub will suffer from fewer diseases.
After using the thinning method for a year or two and you see increased interior growth in a shrub, you may notice that when you pull the outer branches away you'll see a “shrub within a shrub.” Then you can just prune the tall branches lower than the newly-leafing branches, and have a “new shrub” in the landscape. This process results in a continuous renewal of the shrub and a healthy-looking landscape. Important note: To prevent cutting off next year's blooms, some flowering shrubs should be pruned as soon as possible after the bloom period ends. For a complete list of these shrubs and more information on pruning in general, visit Clemson's online Home and Garden Information Center.
Renewal: If you have a shrub that has outgrown its space or needs a new start, you may be interested in trying renewal pruning. This technique involves cutting the entire shrub back to 6-12 inches high. Timing is important; the best time to prune severely is before spring growth begins (mid- to late-February), and can result in abundant new growth by midsummer.
Most broadleaf shrubs (azaleas, camellias, privets, glossy abelia, nandina, cleyera) respond well to renewal pruning. But shrubs like boxwoods, junipers, pines, cypress, cedar, arborvitae, yews and other narrow-leaf evergreens do not respond when severely pruned and may decline. Transplanting, instead of pruning, may be better for these particular shrubs when they overgrow a site. After renewal pruning, and once the new shoots are 6 to 12 inches long, prune the tips to encourage lateral branching and a more compact shrub. It's important to note that shrubs, like all living things, have a life span and will reach a point where pruning can no longer rejuvenate them or save them. If a shrub doesn't respond well to pruning, then consider replacing it.
I hope you will try your hand at pruning. Pick at least one shrub in your yard as an “experiment,” make some cuts, and then see how the shrub responds to those cuts. Your pruning confidence will grow as your shrubs grow and flourish. If you need to hire a qualified pruner, consider contacting a local certified arborist or landscaper who is trained in these pruning techniques.
The Master Gardener's lunch box lecture series will be held at 12:30 p.m. on Monday, Feb. 17, at Trinity United Methodist Church, 2724 Whiskey Road. Local Rosarian and Master Gardener Jane Burckhalter give a talk titled “Roses to Love.” It will include a rose pruning demonstration, information about roses that thrive in the southeast, instructions on rose care (growing conditions, pest and disease control), and an introduction to new rose varieties. This series of free monthly lectures is open to the public, lasts about an hour, and no reservations are needed. Participants are welcome to bring a lunch to enjoy during the lecture. For more information or for gardening questions, call the Master Gardeners at 803-649-6297 ext. 122, email to email@example.com, or visit the office at 1555 Richland Ave. E.
Pam Glogowski moved to Aiken in 2001 from Janesville, Wisconsin, and has been an active Master Gardener volunteer since 2007.