Suckers are vigorous upright growing stems that form at the base of a tree or from the root system causing stems to appear inches or feet from the base of the trunk. They are problematic because they can reduce flowering and fruiting, alter the form of the tree, harbor pests and diseases, and look unsightly.
What Causes Suckers to Form?
Suckers form for many reasons. Sometimes it’s an indication of stress. Damage to the base of the tree or the roots can promote the development of suckers. Some species of tree are just more prone to suckers including crabapple, hawthorn, linden, maple, black locust, dogwood, and most fruit trees.
A primary cause of sucker formation is a vigorous root system. Many trees are grafted to a rootstock that is often ornamentally inferior to the upper portion (called the scion). When the rootstock is not well-matched with the scion it can promote the formation of suckers from the rootstock. These sprouts often look a little different than the upper portion of the tree and if allowed to grow can be very vigorous and may even dominate the tree.
How and When to Remove Suckers
Remove suckers with a hand pruners as soon as they appear from their point of origin. Often this requires pulling a little bit of soil back to find the base and clip it off while still less than 6 to 12 inches in length. If suckers are not removed at their base, the little stub left behind will resprout with multiple shoots making the problem even worse. Suckers grow most vigorously in spring. If only a few suckers are present and relatively small, waiting to prune until early summer can reduce the likelihood of vigorous regrowth, but there will still likely be regrowth later in the season. Regular pruning of suckers throughout the growing season as they appear is the best way to keep them well-managed.
Should I Use "Sucker-Stopper" Spray?
There are products available that claim to prevent suckers from growing. They are typically a specific formulation of a synthetic growth hormone (usually NAA) or a contact herbicide. There has been little research done on the effectiveness of either type of these products. What is known is that even working at their best, they will not eliminate suckers completely and they have the potential to damage the parent plant. For these reasons, they are not recommended for use on ornamental trees.
Never use herbicides to treat or destroy suckers. An application of any herbicide (contact or systemic) to the suckers is likely to damage or kill the tree.
Unfortunately, trees that form suckers will always have suckers. Regular pruning of suckers at their base as they appear is the most effective way to manage them and is just part of the regular maintenance required to keep the tree healthy and attractive.