Tom's Blog

Tuesday, January 20, 2015

Woody plants that produce root suckers

Many woody plants that are rhizomatous produce dormant buds on their roots that are capable of forming new shoots when apical dominance is eliminated. These new shoots may be called basal shoots, root shoots, or adventitious shoots, but they are most commonly called root suckers. This is a property of asexual growth or vegetative reproduction, and is widespread in woody plants, both shrubs and trees. Although root suckering also occurs in herbaceous plants, it is more commonly a problem in control of woody plants, especially ones known to be invasive.

The table below lists woody plants common in our area that form root suckers. Some of these species are relatively benign, but others present major problems in restoration work, as the Notes column indicates. Most of the species in the table are native. Only those noted as Introduced are non-native,

Latin name
Common name
Alnus incana
Swamp alder
Forms “alder” thickets
Amelanchier spp.
Also called serviceberry
Celastrus orbiculata
Oriental bittersweet
Introduced: very invasive
Celastrus scandens
America bittersweet
Elaeagnus angustifolia.
Russian Olive
Elaeagnus umbellata
Autumn Olive
Introduced: Very invasive
Fagus grandifolia
Gleditsia triacanthos
Honey Locust
Populus alba
White Poplar
Introduced: Very invasive; spreading
Populus deltoides
Eastern cottonwood
Populus grandidentata
Big-tooth aspen
Very invasive
Populus tremuloides
Quaking aspen
Very invasive
Prunus americana
Wild plum
Prunus serotina
Wild black cherry
Prunus virginiana
Rhus glabra
Smooth sumacs
Very invasive
Rhus hirta
Staghorn sumac
Very invasive
Robinia pseudoacacia
Black locust
Very invasive
Rubus allegheniensis 
Rubus idaeus
Red raspberry
Very invasive; forms dense clones
Salix exigua
Sandbar willow
Forms dense patches
Tilia americana
Viburnum lentago
Viburnum prunifolium
Native unless indicated otherwise

It is often found that when a clone of a root suckering species is cut or burned, more new shoots will arise than were originally present. Even if the cut stems are treated with herbicide, root suckering will occur. In fact, the treatment seems to have stimulated growth. This is because the rhizomes contain large numbers of dormant buds, and many of them are released when apical dominance is removed.

Knowledge that a woody species root suckers is very valuable in developing a control strategy. It is a key that the "patch" cannot be eradicated by simply cutting and treating. You can be certain that within a month or so, or the following season, root suckers will have grown and must be dealt with. 

Since root suckers themselves are capable of forming rhizomes and shoot buds capable of forming new root suckers, it is essential that the suckers are killed before they have a chance to do anything. Thus, if the original patch was cut in spring or early summer, it must be revisited in late summer and all new suckers treated. If the patch had been cut in late summer/early fall, then it must be revisited in early to mid summer of the following year. To eradicate a patch is at least a three-year job, perhaps longer.

There is some suggestion that root suckering may not occur if the clone is foliar-sprayed with aqueous triclopyr. However, it is difficult with such foliar spraying to prevent damage to "good" plants. In Nebraska, Stubbendieck and associates adapted a sponge applicator to a tractor and were able to eradicate large sumac clones without any peripheral damage.

Aspen is notorious for root suckering. In commercial aspen production, this is considered a "good thing".

Access this link for an excellent U.S. Forest Service manual on aspen ecology and management. This will take you to a page with links to PDF files, for individual chapters or the whole manual. The chapter by George Schier et al. on Vegetative Regeneration discusses root suckering and its control by girdling etc. in detail. Although the manual focuses on Western United States, the same species is present in the Midwest, with the same growth characteristics. 

The principals derived from aspen can be applied to other woody species.


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