Suckers are vigorous vertical growth coming from the roots or lower main stem of a plant. Suckers are usually considered undesirable—you want the plant, but you don’t want its suckers because they sap the plant’s energy.
When you learn to recognize suckers, you’re ready to manage them. You can keep them when you want them, remove them when you don’t, and prevent them from occurring frequently.
Avoiding Suckering Plants
You minimize suckering by planting species or varieties of species that don't sucker often. There are plenty of shrubs and trees that are known for their tendency to produce suckers, such as forsythia, dogwood, roses, sumac and birch. Don’t put one of these species in a sunny lawn and expect to get a specimen shade tree out of it. It wants to spread.
In some cases, you may see a named variety of a shrub that is reported to spread less. Take this information with a grain of salt—“less” might not mean “much less,” but this is still a feature worth looking for.
Suckering can be a desirable thing. In some parts of your garden or in some garden styles where you want a spreading mass or a wild-like thicket, suckering produces that effect. For some, a berry patch, cottage garden or marsh wouldn’t have the right feel without letting some suckering go, and that’s fine.
Keeping Your Plants Healthy
Most trees and shrubs are capable of suckering, but when healthy, they don’t sucker often. Stress awakens the sucker response in almost all of them. Factors most likely to cause suckering are:
- Planting too deep. Trees with root flares should be planted to leave the whole flare above the soil. Trees and shrubs without flares should have the topmost major root just below the surface of the soil. Deeper planting—a common mistake—causes the plant to produce suckers.
- Pruning too hard. If you exceed the typical 1/3 rule of pruning, you’re asking for suckers. By removing so much of the top growth of the plant, you stimulate the plant to try to replace what it has lost.
- Almost anything else that results in the death of a large part of the plant. Disease and pest infestation can do it. Prolonged drought, if it gets to the point of killing, can do it too. This tends to produce suckers, especially in shrubs that we don’t think of as “bushes.”
Removing Suckers on Roses and Other Grafted Plants
On grafted plants, it is most important to control suckers. Many types of roses are commonly grafted and prone to this problem. In these cases, suckers from below the graft union are from the rootstock, which is a different type of plant from the one you bought and want to grow. Worse yet, the rootstock is often a vigorous type of plant, so its suckers can grow quickly and can smother the plant you want with ones you don’t want.
Once you determine that you have a sucker, get a firm grip on it and tear it out by (a leather-gloved) hand. Tearing rather than cutting the sucker rips out the basal dormant buds that would otherwise be left behind to awaken and form new suckers. The earlier you do this, the easier it is.
If your rose is a shrub or “old garden” rose type, it is likely to be growing on its own roots, not a grafted rootstock, so its suckers are just a normal nuisance like those of other plants, and you can remove them as you do on any non-grafted plant.
Removing Suckers on Non-Grafted Plants
Non-grafted plants, or “own-root plants,” are the plants we usually have in our garden. For these plants, you just remove the suckers in whatever way is easiest for you and that results in the tidiest appearance. If you can yank them by hand, that’s still the best and helps prevent the recurrence of suckers. However, once a sucker has lived for a few weeks, it's impossible to remove by hand. It’s just too big and tough or too thorny, such as on honey locust.
In these cases, prune the sucker down to the base as low as you can with the handiest tool. This is usually a pruner or lopper, but if you have a berry patch or other area that is going to have a lot of suckers, buy a woodsman’s pal. It's a machete-like tool that you wield with a swinging motion to quickly cut down a lot of suckers at once. You can’t make precise cuts so it’s only good on fast-growing shrubs in areas that you can let look a little wild. When you have a lot of suckers, though, there’s nothing better for the job.