Using native allelopathic species to combat exotic species

Effective methods of control are lacking for many invasive weeds globally. Finding economic, ecologically sound methods to control these plants is imperative for conservation purposes. Recent research has shown that some exotic European plants in North America produce phytotoxins that may displace North American native plants.  Further, several notorious European weeds from North America reportedly possess allelopathic properties in Europe. Allelopathy may be particularly important in invaded plant communities, where native plants are less likely to have evolved resistance to chemicals introduced by newly arrived species. A corollary of this novel weapons hypothesis is that native allelopathic species could be used as a management tool to displace some exotic plant species, since exotic plants might not be resistant to chemicals from native species. We tested this hypothesis in the greenhouse by growing native plants suspected to be allelopathic in competition with exotic species. In addition, we grew the exotic species and allelopathic native species in mixtures with other native species.  Activated carbon, which adsorbs organic compounds, was used to test for allelopathic effects. Our goal was to determine if the allelopathic species could be used as selective “smother crops” to displace exotic weeds while allowing native species to succeed. Our results suggested that the allelopathic properties of the native species were not strong enough to have discernable effects on the exotic species that were tested.