Date of Graduation


Document Type


Degree Type



Eberly College of Arts and Sciences



Committee Chair

James B. McGraw.


American ginseng (Panax quinquefolius L.) is a long-lived, valuable herb found throughout the eastern United States. Habitat degradation, harvest pressures, overbrowsing by deer and reduced genetic diversity are believed to be the primary causes of decline for this rare species; however the widespread threat of invasive species has yet to be investigated. Therefore, my research focused on examining the level of exposure of individuals and populations of ginseng to invasive plant species as well as partitioning the effects of a particular invasive, garlic mustard (Alliaria petiolata ), into those owing to competition and allelopathy. For my first study, I used a novel plant-centric sampling approach to investigate the level of invasion in 30 natural ginseng populations. I found a high level of invasion both among populations and near individual ginseng plants. I also found a higher probability of previously harvested populations and larger populations to contain invasive species. My second study addressed the competitive and allelopathic effects of garlic mustard on ginseng seedlings. I found that while there was no competitive effect of garlic mustard, there was a tendency for garlic mustard to allelopathically increase mortality in ginseng seedlings. The third study examined how garlic mustard density and leaf litter addition may affect ginseng growth and reproduction. While the extreme garlic mustard treatments showed no significant effect on ginseng growth, increased weight of garlic mustard leaf litter had a tendency to decrease the proportion of flower buds which developed into berries and seeds. The overall conclusions from these studies are that invasive species are prevalent within natural ginseng populations, and ginseng recruitment within garlic mustard invaded populations may be reduced.;Keywords. American ginseng, invasive species, garlic mustard, Panax quinquefolius, Alliaria petiolata.