Suckers at the base of a tree: why natives sucker, and which to keep

Suckers are shoots that rise from a tree’s roots or from the base of its trunk. On pawpaw, sassafras, the sumacs, most native plums and black locust they are the plant’s own way of spreading into a colony. There the planter decides whether to keep a thicket or one trunk. On a tree that normally stands alone, suckers usually follow stress or an injury to its roots or trunk. Cut the unwanted ones where they leave the root, and never spray them with weed killer, which can reach the tree.

Suckers, water sprouts and the shoots after damage

A root sucker comes up from a root, sometimes several feet from the trunk, and other suckers rise from the base of the trunk itself. Water sprouts are the same kind of shoot on the trunk and branches. Both grow from dormant buds in the bark, the epicormic buds that also sprout after a storm or a hard pruning.

Young suckers are weakly attached. Left to grow, they crowd the crown, cut flowering and fruiting, and leave the tree weaker against wind and ice. Their soft, fast growth also draws aphids and fungal disease.

On a grafted tree, the suckers from below the graft come from the rootstock, so they look unlike the tree above and can outgrow it. Blue Whale Trees grows every tree it sells from seed, with nothing grafted, so a sucker from one of our trees carries the same genes as its trunk.

Why a native sends up suckers

Some natives spread that way by nature. Root suckers are how pawpaw mainly reproduces, and its thickets are clones, so a patch in the woods may be a single plant. Staghorn sumac spreads by root suckers into large colonies.

On any tree, suckers can also be a sign of stress. A mower or a string trimmer that wounds the base of the trunk brings them, and so does a serious injury to the crown. Cut roots answer the same way: black locust roots that are cut or mowed sprout freely, and American persimmon roots sucker when cut. Where a tree that never suckered starts to, look for what is stressing it, since that is the surest way to slow them.

The natives we grow that sucker into colonies

These natives we grow spread by their roots, from a low patch to a grove:

• Staghorn sumac colonizes dry banks and road cuts, and one plant becomes a colony as wide as it is allowed. Zones 3 to 8, 15 to 25 feet.
• Fragrant sumac makes a low thicket for dry banks. Zones 3 to 9, 2 to 6 feet.
• Pawpaw grows in colonies in river woods, and a happy pawpaw suckers into a patch. Zones 5 to 9, 15 to 30 feet.
• Sassafras makes a colony in time, fine in a hedgerow but not on a lawn. Zones 4 to 9, 30 to 60 feet.
• American plum sends up root sprouts as much as 10 feet from the parent, and they build its thorny thickets. Zones 3 to 8, 15 to 25 feet.
• Chickasaw plum suckers into dense thickets. Zones 5 to 9, 4 to 20 feet.
• American persimmon sends up suckers where its roots are cut. Zones 4 to 9, 35 to 60 feet.
• Black locust suckers and spreads, and its young suckers carry paired spines. Zones 4 to 8, 40 to 70 feet.
• American hazelnut suckers into a broad thicket. Zones 4 to 9, 8 to 12 feet.
• Bottlebrush buckeye slowly widens into a mound, in time twice as broad as it is tall. Zones 4 to 9, 8 to 12 feet.
• Dwarf chinquapin oak suckers into low colonies, an oak that spreads like a shrub. Zones 4 to 8, 6 to 15 feet.

Not every native plum suckers. Mexican plum grows on a single trunk, hortulan plum rarely suckers, and flatwoods plum usually stands alone as a small tree.

Keep the thicket or keep one trunk

A thicket is the plant’s own shape, and keeping it is a choice, not a failure. A thicket of plum or sumac holds a dry bank, and a suckering plum hedgerow shelters songbirds. Give such a plant room, or a mowed strip where the colony must stop, since mowing keeps suckers down in a lawn.

For one trunk, remove the suckers as they come. Downy serviceberry and nannyberry make single-stemmed small trees that way.

A thicket grown from one root is also one plant when it comes to fruit. Plums need pollen from a second plum, and a thicket from one root counts as one tree, so plant two or more from different seed. A patch of fragrant sumac grown from one plant’s suckers is often all male or all female.

How to take suckers off

Cut each unwanted sucker with sharp pruning shears at or just below the soil line, as soon as it appears. A sucker from a root may need a little digging to reach the place where it leaves the root. Cut it there, flush, since a stub sends up several shoots in its place:

“Ideally, they should be cut back to the point where they emerge from a root or the stem, as leaving a stub can make the problem worse by causing multiple shoots to form.” (University of New Hampshire Extension, Can water sprouts and suckers be prevented on trees?)

Suckers can come off in any season. The dormant season, when the plant’s shape is easiest to see, and early summer, once the spring growth has hardened, are the usual times. Mow those that come up in a lawn, but keep the mower and the string trimmer off the trunk, since a wound at its base brings more suckers.

Never spray a sucker with weed killer. A sucker draws on the same roots and sap as the trunk, so what it takes up reaches the tree:

“Never use glyphosate to remove suckers growing from the rootstocks of grafted trees. They are directly connected to the tree’s vascular system, and such applications will damage the tree or possibly kill it.” (Penn State Extension, Use Glyphosate With Care Near Trees!)

Expect to repeat the work, since a tree that starts to sucker usually keeps on for the rest of its life.

Where to start

Decide first whether the plant may spread, then:

• A thicket for a bank or a fence line: the tree finder lists the natives we grow that hold soil, most of the colony-formers above among them, by zone, size and sun.
• The same plants side by side: the shop’s erosion control list shows them with their zones and heights.
• One trunk beside a lawn or a walk: a plum that stays put, such as Mexican plum, or any colony-former kept to one stem by cutting its suckers as they come.

Common questions

What is the difference between a sucker and a water sprout?

A sucker comes up from the roots or the base of the trunk, and a water sprout grows from the trunk or a branch. Both rise from dormant buds in the bark, often after stress or an injury.

Should I remove suckers from the base of my tree?

Yes, if you want one trunk: cut each one where it leaves the root or the trunk, as soon as it appears. On pawpaw, sumac or a wild plum you may keep some, since a thicket is how those plants grow.

How do I stop suckers from growing back?

Cut each one flush at its point of origin, since a stub sprouts again, and keep mowers and string trimmers off the trunk. A tree that has begun to sucker usually keeps on, so plan to cut them regularly.

Do sucker stopper sprays work?

The sprays carry NAA, a synthetic plant hormone that slows the regrowth from a cut. Penn State Extension suggests one on fresh cuts, while New Hampshire Extension notes that little research has tested them on landscape trees.