Many shrubs can be pruned in spring
By John J. Forshee
River Valley District Extension Director, Horticulture
As warmer weather arrives, gardeners are eager to get out and get some yard work done. One task that can be done this time of year is pruning of many of our shrub species. The first step is to distinguish between the deciduous (those that lose their leaves) and evergreen varieties.
Evergreens, including junipers and yews, can be pruned in the spring. Juniper species are a challenge as they do not have lateral buds. One must never cut back beyond the green growth at the outer end of the stems. Pruning too aggressively on junipers will result in holes or “dead” areas of the shrub that will never recover.
Deciduous shrubs must be divided into two groups: 1) those that flower in the spring on wood produced last year, and 2) those that flower later in the year on the current season’s growth or those that have little or no ornamental value to their flowers.
Shrubs that flower early in the spring should not be pruned until immediately after flowering. Shrubs that fall into this category are lilac, Vanhoutte or Bridal Wreath spirea, forsythia, and mock orange. Pruning immediately after blooming will allow these shrubs to grow new wood throughout the remainder of the spring and summer, providing an abundance of blooms the following year. Pruning in summer, fall, or early winter will eliminate the wood for blooming and should be avoided if possible.
Shrubs that bloom in late spring and summer, or those that have little or no ornamental value to the flowers, can be pruned in March. Examples of this would be Rose-of-Sharon, pyracantha, boxwood, and many of the newer spirea shrubs that bloom throughout the summer.
Shrubs can be pruned to maintain or reduce size; rejuvenate growth; or to remove diseased, dead, or damaged branches. Winter or early spring pruning allows the wounds to heal quickly without threat of disease or insect invasion. One question we often get is, “Should I paint or treat the wound site when I prune off branches?’ Although this was once recommended, there is no research that backs this up. Some foresters suggest that it might actually impede the healing process in some cases. If pruning out diseased wood, it is important to disinfect the pruning tools between cuts and as you move from one shrub to another. A simple 10 percent bleach solution is all that is needed. (1 part household bleach to 9 parts water) Be sure to oil the pruning tools after use as this bleach can cause the tools to rust.
Extension Bulletin C-550, All About Pruning (http://www.ksre.ksu.edu/bookstore/pubs/c550.pdf), has great, timeless information and graphics to provide guidance in pruning shrubs and trees.