Pruning woody plants is one of the most important things that you can do for maintaining your landscape trees and shrubs. Pruning involves a combination of art and science — art in making the pruning cuts properly, and science in knowing how and when to prune for the overall health of the plant.
All woody plants exert control of the growth of their limbs by a hormone produced by the plant. The terminal bud of a limb controls the growth of the lateral buds on the same limb. This is what gives trees a natural form. The amount of control or apical dominance varies from one species to another. One of the best examples of this is the form of a pine tree versus a dogwood. Apical dominance is stronger in the pine tree.
Pruning is an invigorating process for the plant. By removing the tip of a limb, apical dominance is temporarily destroyed and lateral buds are given a chance to sprout and grow into shoots. The more you prune on a plant at one time the more vigorous growth occurs. The plant is trying to bring the above-ground growth in balance with the root system.
There are two basic types of pruning cuts: heading and thinning. Heading removes the terminal portion of shoots or limbs. By removing apical dominance, heading stimulates regrowth near the cut. The result of heading is a thick, compact growth and loss of natural form, as in the case of a formally pruned hedge.
Thinning is different from heading because you remove an entire shoot or limb to its point of origin from the main branch or lateral. Apical dominance is maintained, and as a result new growth occurs at the undisturbed shoot tips while lateral bud development and regrowth is suppressed.
When you make a thinning cut, be sure to make the cut just in front of the bark ridge (top side of the branch) and the branch collar (bottom side of the branch). If you cut into the bark ridge or branch collar, you will increase the surface area of the cut and the time the tree has to heal itself. If you cut too far ahead of these areas, then you will leave a stub, which will be a source of infection and insect pressure. Leave the pruned areas alone after you have made the cut. Pruning paints are cosmetic and do not promote healing.
Many woody ornamentals are pruned according to their date of flowering. Spring-flowering plants, such as dogwood or forsythia, normally are pruned after they bloom. If they are pruned during the dormant season, you will remove the flower buds that were formed the previous growing season.
Summer-flowering plants are generally pruned during the dormant season. Avoid heavy pruning during the later summer or fall because regrowth may occur and make the plants more susceptible to cold injury.
Even though this is not the time of year to prune, it is good to get ready for it and look at your trees and shrubs in a whole new way.
Michael Wheeler is county extension coordinator for the UGA Cooperative Extension in Hall County. You can contact him at 770-535-8293, www.hallcounty.org/extension. His column appears weekly and on gainesvilletimes.com/life.