Plant suckers are vigorous vertical growth originating from the root system or lower main stem of a plant. Plant suckers are usually undesirable—you want the plant, but you don’t want its suckers because they sap the plant’s energy.
When you learn to recognize plant 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.
Alternatives to Plants That Produce Suckers
Most plants, trees, and shrubs will develop plant suckers to propagate or spread new growth. Often if a tree sustains a pruning wound, it might even send out a sucker in that spot of the trunk as a way to heal. If the roots have been damaged, you might see suckers grow from the base of the trunk.
However, some plants are less likely to develop plant suckers than others. Several species of lilacs, like late lilac, Meyer lilac, Peking lilac, and Manchurian lilac, rarely produce plant suckers. Similarly, several broadleaf evergreens, such as rhododendrons or strawberry shrub, and Hydrangea paniculata, sucker less than other plants. Oak trees can develop plant suckers but not as frequently as other trees.
Don't Plant Suckering Plants
You minimize plant suckering by planting species or varieties of species that don't sucker often. Plenty of shrubs and trees are known for their tendency to produce plant suckers, such as forsythia, dogwood, roses, sumac, and birch. Don't plant 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 might see a named variety of a shrub that is reported to spread less. However, be aware that "less suckering" might not mean "much less," but this is still a feature worth looking for.
Plant 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 some suckering plants, and that's fine.
Keeping Your Plants Healthy
Most trees and shrubs can produce suckers, but they don't often sucker when healthy. Stress awakens the sucker response in almost all of them. Factors most likely to cause plant suckering are:
- Planting too deep: Trees with root flares should be planted to leave the whole flare above the soil surface. Trees and shrubs without flares should have the topmost major root just below the soil's surface. Deeper planting—a common mistake—causes a plant to produce suckers.
- Pruning too hard: If you exceed the typical 1/3 rule of pruning, you're encouraging plant suckers. By removing too much of the plant's top growth, you stimulate the plant to try to replace what it has lost.
- Plant disease or infestation: Disease and pest infestations can cause suckering. Prolonged drought, if it gets to the point of killing the plant, can cause suckering too.
- Grafting union failure: When grafting unions fail, if the rootstock is still healthy, it will attempt to branch and leaf out, resulting in suckers or slender vertical branch growth from the rootstock.
Removing Suckers on Roses and Other Grafted Plants
On grafted plants, it is most important to control plant suckers. Many types of roses are commonly grafted and prone to this problem. In these cases, plant suckers below the graft union are coming from the rootstock, which came from a different type of plant than 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 desirable plant with one that you don’t want.
Once you see a plant 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 regular 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 remove the plant suckers in whatever way is easiest for you, resulting in the tidiest appearance. If you can pull them out by hand, that's still the best method and helps prevent the recurrence of plant suckers. However, once a sucker is established 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.
if the sucker has established itself, prune it down to the base as low as possible with the handiest tool. You can use a pruner or lopper, but if you have a berry patch or other area that will have a lot of plant suckers, buy a woodsman's pal. It's a machete-like tool that you wield with a swinging motion to quickly cut down several suckers at once. You can't make precise cuts, so the tool is only useful on fast-growing shrubs in areas that can be left wild. However, if you need to remove a lot of plant suckers, though, there's nothing better for the job.
Pruning Suckers off Tomato Plants
Tomato suckers are the side-shoot growths that appear in the junction between the stem and a branch of a tomato plant called the axil. In theory, tomato plant suckers sound like a good thing. More stems could potentially mean more fruits. However, plant suckers are problematic because the new stem will be consuming water, nutrients, and energy from your growing tomatoes. Just know, if you let the plant suckers continue to grow, your tomatoes will be smaller.
Additionally, too much tomato foliage reduces airflow. Tomatoes are susceptible to a broad range of viral, bacterial, and fungal conditions, and disease primarily thrives in prolonged moisture environments. Pruning away suckers keeps air circulating and helps leaves dry quicker, reducing an overly-moist environment.
To remove tomato plant suckers, snap them off when they are two to four inches long. Use a pruner to remove any stems thicker than a pencil. Sterilize your pruners before and after use.