Beware of Suckering Trees and Shrubs

Larry Hodgson published thousands of articles and 65 books over the course of his career, in both French and English. His son, Mathieu, has made it his mission to make his father’s writings accessible to the public. This text was originally published in Le Soleil on August 28, 2005.

---

Some trees and shrubs, can be aggressive and invasive. All gardeners know this, or they’ll learn it sooner or later. And many problems can be avoided if you know this before you plant.

Suckering Trees and Shrubs

A sucker is a plant that develops at some distance from the mother plant, on a stolon or root of the latter. And a sucker can quickly produce others. So what was an isolated tree or shrub gradually becomes a forest, if left to its own devices. Conifers never sucker. So you can assume that the conifer you plant today will always stay where it is. And most deciduous trees and shrubs don’t sucker either, but there are several exceptions. These plants produce “babies” everywhere: in the lawn, the flowerbed, the vegetable garden and so on. Their roots can even run under a driveway or sidewalk to produce suckers on the other side. You’ll soon wonder why you ever planted them in the first place!

Suckers that appear close to the mother plant are generally considered by gardeners to be of little disturbance: the plant becomes denser with time, that’s all. But other plants produce suckers far from the mother plant: one metre, two metres, even more. The world champion of aggressiveness is our own Quaking Aspen (Populus tremuloides). These suckers commonly appear 20 m (65 ft.) from the original tree, and sometimes up to 80 m (260 ft.)!

Natural or Induced Suckering?

Curiously, not all the plants mentioned above are suckers in all circumstances. Many only become “aggressive” if their roots are injured. So, where we usually weed – in a flowerbed, for example – these plants proliferate. Where they are not weeded, such as in a lawn, they pose no problem. Also, more modern gardeners who use mulch in their beds instead of weeding have no problems with these “provoked” invaders either.

Controlling Suckers

Suckers can of course be controlled by cutting them back and pulling them out where they grow. But it makes a pretty mess of a lawn! And when you remove suckers, it stimulates the mother plant to produce even more. As with everything, prevention is easier than cure.

You can simply avoid invasive woody plants. For example, rather than planting the suckering false spiraea (Sorbaria sorbifolia), you could choose its cousin, the Aitchison sorbaria (Sorbaria tomentosa var. angustifolia, also sold under the name S. aitchisonii), which rarely produces suckers. And of all the lilacs, only the common lilac (Syringa vulgaris) is suckering. The Tiger Eye Sumac (Rhus typhina ‘Bailtiger’ Tiger Eyes) does not sucker, while the other sumac trees (R. typhina and R. glabra) are all very suckers.

If, despite everything, you like a suckering shrub or tree so much for its other qualities that you want to plant it anyway, it’s possible to control it. To do this, take advantage of a curious phenomenon: only the superficial roots of woody plants suckle. Those that go deeper never do. If you can limit the growth of the superficial roots without preventing the other roots from growing, you can cultivate the plant for its other attractions without worrying about its aggressiveness.

What to Do?

Plant it inside an impenetrable barrier. For a shrub, a large plastic bucket with the bottom cut off is suitable. For a tree, you’ll need to look for something even bigger, like a large plastic bowl or even (no joke!) a large upright sewer pipe. When planting, therefore, we first dig a hole wide and deep enough to place our “barrier”, leaving only a thin margin of 2.5 to 5 cm (1/2-1’’). We’ll cover this area with mulch later).

When you plant invasive woody plants inside such a barrier, they can sometimes fill this space with suckers, but the surrounding ground will be completely free of them.

When Suckering Is a Good Thing

In the city, we seldom appreciate aggressive plants, so suckering woody plants get bad press. But on the water’s edge, where erosion is a problem, or on a sand dune, they are invaluable friends. In fact, by suckering, they stabilize banks and dunes and prevent future erosion.

So, suckering can be good or bad, depending on your situation, but at least you’ll know the true nature of the plant the next time you store for a tree or shrub for your property!

Examples of Suckering Trees and Shrubs

• Serviceberry (Amelanchier canadensis), zone 4 (4 to 8 USDA)
• Running serviceberry * (Amelanchier stolonifera), zone 3 (4 to 8 USDA)
• Chokeberry (Aronia spp.), zone 4 (3 to 8 USDA)
• Sea buckthorn* (Hippophae rhamnoides), zone 2b (3 to 8 USDA)
• Chokecherry* (Prunus virginiana), zone 2b (3 to 7 USDA)
• Fire cherry* (Prunus pensylvanica), zone 2 (2 to 5 USDA)
• Silverberry* (Elaeagnus commutata), zone 1b (2 to 6 USDA)
• Tatarian dogwood (Cornus alba), zone 2 (3 to 7 USDA)
• Bloodtwig dogwood (Cornus sanguinea), zone 3 (4 to 7 USDA)
• Red twig dogwood* (Cornus sericea, syn. C. stolonifera), zone 2 (3 to 7 USDA)
• Raspberry* (Rubus idaeus) zone 3 (4 to 8 USDA)
• Golden currant (Ribes aureum var.villosum), zone 2 (4 to 8 USDA)
• Common lilac* (Syringa vulgaris), zone 2b
• Bog-myrtle* (Myrica gale), zone 2 (2 to 9 USDA)
• Balsam poplar (Populus balsamifera), zone 2 (1 USDA)
• Black poplar * (Populus nigra italica), zone 4
• American aspen* (Populus tremuloides), zone 2 (1 to 6 USDA)
• Black locust (Robinia pseudoacacia), zone 4b (3 to 8 USDA)
• Brambles* (Rubus spp.), zone 3 (4 to 8 USDA)
• Rugosa rose*, certain cultivars (Rosa rugosa), zone 3 (2 to 7 USDA)
• Silver buffaloberry * (Shepherdia argentea), zone 2 (3 to 9 USDA)
• False spiraea * (Sorbaria sorbifolia), zone 2 (2 to 8 USDA)
• Fragrant sumac* (Rhus aromatica), zone 3 (3 to 9)

Plants marked with an asterisk (*) are the most “aggressive”: they invade even when care is taken not to disturb them.