Garlic mustard. Is Alliaria allelopathic?
Garlic mustard (Alliaria petiolata) is an invasive alien species that dominates the floor of many forests in Pennsylvania, to the detriment of native species. The effectiveness of this species in quickly taking over the herbaceous layer has led to speculation that it may exude chemicals that inhibit the growth of other species, a mechanism called allelopathy. Although several potentially allelopathic* compounds have been isolated from garlic mustard (Vaughn and Berhow, 1999), research to date has not provided convincing evidence that allelopathy is a significant factor in the invasiveness of garlic mustard (McCarthy and Hanson, 1998). Perhaps garlic mustard is simply better at competing for resources such as light, water and nutrients; and, because it is away from its homeland, it lives in absence of its usual controls, e.g. insecs that eat it. More research is needed. We have much to learn about the invasive species that have become such a conspicuous feature of our landscape in the past few decades.
*Allelopathy: The chemical inhibition of one organism by another (Linclon et al, 1987). Black walnut is a well-known example of an allelopathic plant; gardeners know it is difficult to get anything to grow near a black walnut tree.
Literature Cited:
McCarthy, B.C. and S.L. Hanson. 1998. An assessment of the allelopathic potential of the invasive weed Alliaria petiolata (Brassicaceae). Castanea 63:68-73.
Vaughn, S.F. and M.A. Berhow. 1999. Allelochemicals isolated from tissues of the invasive weed garlic mustard ( Alliaria petiolata ). Journal of Chemical Ecology 25:2495-2504.
Lincoln, Roger, Geoff Boxshall, and Paul Clark. 1987. A Dictionary of Ecology, Evolution and Systematics. Cambridge University Press.
The garlic mustard highlighted today is a photo taken by WPC Ecologist Robert Coxe.
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