If you see a profusion of sprouts (suckers) at the base of a tree, it can mean nothing at all . . . but can also be a symptom of serious problems.
By Larry Hodgson
To most people, a tree has one trunk. It grows straight up for a certain distance, then it branches. So, one trunk, one tree. And most temperate climate trees do grow that way.
But sometimes you see sprouts appearing from the base of the tree or from its roots. Horticulturists call them suckers, as they use some of the nutrients that would otherwise go to the main tree. Still, they rarely do major damage, but you might want to keep them under control.
Certain trees naturally tend to sucker. If you leave them alone, they may end up looking more like a multi-stem shrub than a tree! In fact, many actually grow as large multi-stemmed shrubs in the wild. Nurseries only turn them in “trees” by careful pruning. A few of the shrubs thus turned into trees and sold as such in garden centers are Amur maple (Acer tataricum ginnala), Japanese tree lilac (Syringa reticulata) and Canadian serviceberry (Amelanchier canadensis).
Stress Leads to Suckering
But other trees mostly sucker only when under stress. And that’s a situation where you should keep your eyes peeled.
Prolonged or repeated drought, saline soil, damage to the upper branches or any major dieback all tend to stimulate increased numbers of suckers. So will heavy pruning. Dying trees in general, even if it’s simply from old age, tend to produce suckers, as if it were a last chance to save their life.
Suckering is also one of the major symptoms we associate with emerald ash borer. As the invading insect bores into an ash (Fraxinus spp.) tree’s upper branches, the tree often sends out suckers from the ground or lower on its trunk* to compensate. All to no avail: once an ash tree reaches the suckering stage, it can no longer be saved.
*Suckers that appear from the trunk rather than its base or its roots are called water sprouts in horticultural lingo.
Be especially concerned when a tree that never suckered in the past starts producing them. It may well be under attack. It would be worthwhile having an arborist inspect it.
The best way of removing suckers is simply by cutting them off at the base with pruning shears. You can do this at any season, preferably when they are still young. (Larger ones leave a bigger wound that is more likely to become infected with a fungus or other disease.) If it sprouts from underground, you can often pull up on them or knock off a bit of soil to reach the spot where they join the root for the closest possible cut.
As for those that pop up in the lawn that surrounds the tree, you can often simply clip those back with the lawn mower. Or if the roots are truly far ranging, pull a few roots out entirely.
Don’t try spraying suckers with a herbicide (weedkiller), though. They’re still attached to the mother tree and weedkillers can migrate from the sucker to the tree itself and damage it.
And cut suckers again when they resprout. There really is no way of elminating them permanently.
If You Want to Keep the Sucker. . .
I’ve written the above as if it were obvious that you would want to remove the sucker. But you don’t have to. If you don’t mind your tree changing its shape (it will likely become denser, like a clump rather than an individual tree, if there are several at its base), that’s fine.
Of course, those that show up here and there sprouting from the tree’s vast root system could eventually lead to entire forest growing (aspens do that!), thus permanently changing the use of that sector. And that will be good or bad, according to your interests. I love my cutleaf staghorn sumac (Rhus typhina ‘Laciniata’), for example, but I scrupulously mow down and cut back its suckers. One is plenty, thank you!
And if an ancient tree is dying and you’re hoping the sprout will replace its mother, be forewarned that the root system it inherits may be a weak one and that it might therefore not survive long. Or that it may hang on for ages, but grow only weakly. Plus, many decades will probably go by before it reaches the impressive size of the mother tree.
When a young tree dies unexpectedly, though, and you let one single sucker grow on, you can often create a very nice remplacement fairly quickly!
Graft Traits Aren’t Carried Over to the New Tree
If the sucker comes from a grafted tree (most fruit trees, many flowering trees and trees with variegated or colorful foliage or a weeping habit are in that category), the sucker is mostly likely from the rootstock and therefore won’t be identical to the top growth. So, say, your crabapple with double pink flowers may well produce suckers with plain white ones while the suckers from that cute little weeping caragana will just grow straight up without ever weeping.
So, study your tree’s habits and take note if it suckers. If it belongs to a species known to sucker, like black locust (Robinia pseudacacia), little leaf linden (Tilia cordata) or staghorn sumac (Rhus typhina), you’re probably already used to it suckering. But if this habit is something new, there might be something wrong. And it may be time to call in a certified arborist.