One of the most daunting tasks of maintaining a beautiful landscape can be knowing how and when to prune shrubs. Not all plants need an annual haircut and not all plants are pruned in the same fashion. Making things worse, there is no formula to beautifully pruned shrubs — pruning has to do with making judgments and having an eye for the final result.
In this article are some guidelines for pruning. It is very important to put the right plant in the right place. Most pruning questions result from a plant outgrowing its space. There are many, many plants with excellent features — nice foliage, great flowers, good fall color, attractive bark — chose one that meets your criteria and, at maturity, will fit in its designated area. This will drastically cut down on the amount of maintenance pruning you will need to do.
There are some general guidelines to follow for pruning. First, trees and shrubs that bloom in the spring and early-summer should be pruned after bloom (azaleas, camellias and hydrangea). Plants that bloom in late-summer and fall should be pruned in the spring. Trees that do not flower should be pruned (if necessary) in the dormant season before sap flow (which begins in mid-winter and runs until midsummer). Conifers (junipers, false cypress, pines, etc.) should only be pruned if absolutely necessary — many will not produce new growth from old wood. Damaged or dead wood can be removed at any time.
Before making any pruning cuts, make sure your pruning tools are sharp. Dull equipment can actually cause more harm by tearing bark or making uneven cuts. All cuts should be made as close to a bud or shoot as possible without injuring it. Do not leave stubs — these will die and can harbor disease-causing organisms. Flush cuts with the trunk should not be made on trees or large shrubs. On shrubs with opposite leaves, cut straight across the stem slightly above the buds. On shrubs with alternate leaves, cut at an angle, parallel with the remaining bud. New growth will be forced into your remaining buds, so be sure to pick buds that will produce growth in the desired direction (for example, if you are trying to thin out the canopy, do not pick buds that will send growth into the shrub).
Keep in mind that pruning will stimulate growth. If you want to shorten a shrub, prune to below your desired height. This way the plant can grow into the height.
There are some common problems that are easy to identify and remove. Any dead, diseased or damaged growth should be removed. If there is a clear definition between live and dead wood, cut to just above this mark. If not, cut into healthy wood where there is no discoloration. With diseased shoots, be sure to cut back into healthy wood and sterilize pruners between cuts!
Unless you are trying to create a barrier shrub, remove crossing and crowded branches. Look for reversions, shoots that have changed back to the parent species (for example, green leaves in a variegated shrub) and remove them during the growing season.
Many shrubs sucker naturally. Suckers should be removed from trees, if a single trunk is desired. With shrubs, these new suckers can replace older branches. Remove suckers that are growing outside the desired spread of the shrub. Also, if the tree or bush is grafted, remove suckers from the ground since these can out compete the desired shrub.
Lastly, do not apply pruning paints! These have not been found to keep out air or water and will not lessen chances of disease. Make proper pruning cuts, however, will allow natural chemicals to defend the plant against invaders.
Pruning can be a difficult process. To make your work easier, plant trees and shrubs that fit your landscape. Then, prune only when necessary or when you spot common problems that must be fixed. For more information on pruning, reference AG-71: Pruning Trees & Shrubs or contact our Center at (919) 775-5624.
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