Background/Question/Methods:
Invasive plants represent a serious threat to community diversity. These highly competitive species often suppress the growth of native species, forming dense monocultures and altering ecosystem dynamics. Aggressive invaders may employ a number of strategies to reduce success, recruitment, and population growth of competing native species, including negatively affecting germination rates and preventing seedlings from reaching maturity. In this study, we focused on Japanese knotweed (Polygonum cuspidatum) an easily identifiable invasive species common throughout Europe and currently increasing in abundance in North America. Previous work suggests that the closely related giant knotweed (Polygonum sachalinense) produces allelopathic chemicals.  We sought to determine whether P. cuspidatum altered soil and affected the germination and growth of three wildflower species native to New England, possibly through an allelopathic root exudate. We collected soil from beneath and adjacent to local stands of P. cuspidatum and crossed these soil types with an activated charcoal or control treatment.

Results/Conclusions:
The preliminary results show a number of interesting trends. For two of the native species Aster lateriflorus (Calico aster) and Helenium flexuosum (Purple-headed sneezeweed) the results were as expected. Both species showed significantly lower germination and growth rates (P < 0.05) in soil collected from P. cuspidatum stands and increased germination and growth rates in the presence of activated charcoal. The third native forb, Monarda fistulosa (Wild bergamot), had significantly higher germination rates in P. cuspidatum soil but lower growth rates (P < 0.05). These results suggest that the presence of P. cuspidatum may negatively affect the germination and growth rates of some native species. However, M. fistulosa may have specialized adaptations to the presence of specific allelopathic compounds that allow for high germination rates.