Springtime pruning of deciduous shrubs
Shrubs and trees can benefit from periodic pruning for a variety of reasons. Sometimes the plant has outgrown its place in the landscape, or there are dead branches that need to be removed. Other times, shrubs and trees need pruning to maintain their shape or to promote new growth. While we recommend that homeowners use a Certified Arborist to prune large trees, the homeowner generally can safely prune shrubs.
Late winter or early spring, before the plants have started their seasonal growth, is generally the best time to do most of your pruning. At this time of year a deciduous plant is easier to prune, since there are no leaves and you can better see the plant’s structure. However, even if you miss this window, most plants can be successfully pruned at other times of the year.
The pruning tools you need will depend on the size of the plants that need pruning. Bypass hand pruners can be used to cut branches up to about ¾” diameter. They have two sharp blades that cross each other like scissors do when closed and give a cleaner cut than anvil pruners, which have only one cutting blade. Bypass loppers are similar to bypass pruners, but they have long handles that sometimes are extendable. Loppers can reach further than pruners and can cut up to 1½” branches. For thicker branches you will need a pruning saw. A wide variety of hand saws are available, including folding saws, which are easy to store and carry.
While a warm day in late winter or early spring is the ideal time to do most of your pruning, dead branches that create a safety hazard should be removed immediately. Also, shrubs that bloom in the spring or early summer should be pruned shortly after they flower, since the buds are generally formed on the prior year’s growth. Plants that flower in mid-summer or later generally can be pruned early in the year, since their buds are formed on the current year’s growth. If you are unsure about whether your shrub should be pruned before or after blooming, first, correctly identify the plant, and then check with your local garden center, online nursery, or the Delaware County Master Gardener’s Helpline at 740/833‑2030.
There are two general types of pruning cuts; 1) heading and 2) thinning.
Heading or heading back removes only part of the branch. The cut should be made about ¼” above a bud to promote new growth. Unless you are trimming a formal hedge, you should avoid “topping” a shrub with a hedge trimmer, since it destroys the plant’s natural shape. Shearing with a hedge trimmer also increases branching on a plant’s exterior, shading the interior and eliminating new growth in that section of the shrub.
Thinning removes an entire shoot or branch at its point of origin at the ground or on a larger branch. Thinning the center of a shrub will enable light to reach its center and promote new growth. Also, the increased air circulation can improve the plant’s health by discouraging pests and diseases. Crossing branches should also be removed.
When multi-stemmed deciduous shrubs have been neglected or incorrectly pruned, the plant can be renewed by removing the older stems at ground level. Heading cuts that trim back the stems by 1/3 to ½ and are made slightly above a bud will stimulate branching. The entire renewal process can take up to three years, if it is done slowly and correctly. In general, never remove more than 1/3rd of a shrub or tree when pruning. However, if a fast-growing multi-stemmed shrub has been neglected for several years and becomes a thick tangle of branches, the only to rejuvenate the plant may be to cut it back to the ground. New shoots will emerge to form a new bush. These shoots will need to be thinned and the plant will need to be pruned on a regular basis to form an attractive bush.
If you are in the process of planning a new foundation planting bed or an addition to your landscape, your choice of plants can determine the amount of maintenance-related pruning that is required. Slow-growing shrubs need less pruning.
They also take longer to fill in the landscape. Therefore, you might want to plant larger specimens. Your local garden center can give you advice on pruning and plant growth habits.
Pick a date in late winter or early spring and mark it on your calendar to remind yourself when it’s time for spring pruning. Remember to enjoy the colorful blossoms on spring blooming shrubs, such as forsythia and lilac, and wait to prune them shortly after the flowers fade. Prune your shrubs or trees so that they maintain their natural shape. If you develop an annual pruning routine, your garden will look much neater, and the job will be more manageable.
Nancy F. Traub is an OSU Extension Master Gardener volunteer.