Spring is a time when we traditionally do some thorough cleaning around the house — washing windows, scrubbing floors and cleaning out cluttered closets. But did you know that spring can also be a great time to give trees and shrubs a little cleaning? Homeowners typically spend a great deal of time working in their yards during the spring, cleaning up their planting beds, picking up sticks and applying mulch. This is also when the phone starts ringing in the offices at tree service companies.
For arborists “cleaning” means to prune out dead, dying, diseased and broken branches from a tree or shrub. Although cleaning can be done any time of the year, spring is an excellent time, just before the plant puts out a new flush of growth.
If your goal is to maximize flowering on spring-blooming trees, however, prune just after your tree or shrub has finished flowering. Pruning after flowering avoids cutting off the flower buds for next year. The general rule of thumb to prune just after flowering can also be applied to plants that flower later in the season.
Most routine pruning to remove weak, diseased or dead limbs can be accomplished at any time during the year with little effect on the tree. Some trees, such as maples and birches, tend to “bleed” if pruned early in the spring. This may be unsightly, but it is of little consequence to the tree.
A few tree diseases, such as oak wilt, can be spread when pruning wounds allow spores access into the tree. Susceptible trees should not be pruned during active transmission periods.
Heavy pruning just after the spring growth flush should be avoided. This is when trees have just expended a great deal of energy to produce foliage and early shoot growth. Removal of a large percentage of foliage at this time can stress the tree.
Newly planted trees
Pruning of newly planted trees should be limited to corrective pruning — removing torn or broken branches. Save other pruning measures for the second or third year.
The belief that trees should be pruned when planted to compensate for root loss is misguided. Trees need their leaves and shoot tips to provide food and the substances that stimulate new root production. Unpruned trees establish faster, with a stronger root system, than trees pruned at the time of planting.
Standards and best practices
All arborists in the U.S. should own a copy of the “American National Standards Institute A300 Standards Part 1: Pruning.” This is the national pruning standard of practice and for writing pruning specifications. The standard can be purchased from the Tree Care Industry Association. Another recommended guide is the International Society of Arboriculture’s “Best Management Practices: Pruning.” This BMP and the ANSI A300 Standard can both be purchased online from the International Society of Arboriculture.
Editor’s note: This article was originally published in May 2013 and has been updated for accuracy.