Proper Pruning Principles
Pruning your shrubs and trees can be a scary thing, but pruning is necessary to maintain healthy trees and shrubs. Pruning can be quite easy if you understand the basic principles of why, when and how. There are several reasons why you would want to prune your shrubs and trees. Your tree or shrub may have become overgrown and weak for the intended space or even become a safety hazard. Pruning can help you manage or reduce the size of your plant. Always remember to prune off the dead, diseased, or damaged branches whenever you see them. Pruning can help certain shrubs and tree to promote flower buds for the flowering season. Lastly, some plants are grown for a particular shape or form such as espaliers or topiaries; pruning and shearing can be used to help shape these forms.
Knowing when to prune is a key factor for having healthy vigorous plants. Most plants can be pruned at almost any time of the year without jeopardizing the plant’s basic survival but it is preferable to prune certain specific plants at a specific time. The time to prune is based on the flowering, fruiting, or growth habits of the plants and whether or not it “bleeds”. The rule of thumb for trees and shrubs that flower before the end of June (spring-flowering) is prune right after it finishes flowering. Some examples of spring flowering plants are forsythia, flowering dogwood, azalea, and Rhododendron. Summer flowering plants, plants that bloom after the end of June, should be pruned in winter or early spring before the new growth starts. These plants include butterfly bush, crape myrtle, hollies, and nandinas. For a complete list of what to prune and when, please visit the cooperative extension website at ces.ncsu.edu. In general, pruning should be done just before regrowth. Pruning late or during the incorrect time can cause wounds, which makes the plant susceptible to diseases. Another adverse effect of incorrect timing is new regrowth that could die out from frost. Any trees or shrubs that have been damaged by a recent storm should be pruned as soon as possible.
There are two types of pruning cuts. Thinning completely removes some branches to its point of origin of the main branch, trunk, or soil line. A thinning pruning will cut off any lateral bud growth and refocus the nutrients and growth into the undisturbed shoot tips. Thinning cuts are generally used to shorten limbs, improve light penetration into plants, and redirect growth. Heading pruning involves shortening branches to a good bud or lateral branch. Heading is used to control the size of the bush, resulting in thick compact growth. Other types of heading are topping, hedging, and clipping.
Use the “one-third” rule as a guide of how much to prune off. Try not to take off more than one-third of the plant; doing so could be stressful to the plant. For cutting large tree branches, use the double cut technique; make a small cut halfway on the underside of the limb, then make a second cut several inches further out onto the upper part of the limb. By doing this, you are reducing the risk of the bark peeling off the tree.
Remember, tree work can be dangerous. Leave the big jobs to the experienced professionals.
Need more resources?
Read about specific pruning trees and shrubs with this publication: http://content.ces.ncsu.edu/how-to-prune-specific-plants