Alliaria petiolata (garlic mustard) is a biennial plant that is invasive in woodland areas in the Midwestern and Northeastern United States. Garlic mustard has been shown in previous studies to inhibit fungal and microbial growth. It therefore seems plausible that garlic mustard may alter the metabolic function of the soil microbial community and may impact these communities early during its biennial life-cycle. To address whether either of these possibilities occur, garlic mustard and a common native woodland plant, Ageratina altissima (white snakeroot), were grown from seed in soil collected from Iowa woodland plots free of garlic mustard in a controlled environment. After three months of growth, the soil was analyzed with Biolog EcoPlates to determine if garlic mustard seedlings impacted the metabolic profile of the soil microbial community differently than white snakeroot. An ANOSIM determined that garlic mustard and white snakeroot treatments had different effects on metabolic profiles of the soil microbial communities (p = 0.001, R = 0.301), and that garlic mustard depressed the metabolic potential of the soil microbial community. Additionally, the extent to which garlic mustard inhibits native plant growth while also stimulating the growth of subsequent generations of garlic mustard was studied. The growth of white snakeroot and garlic mustard were compared when grown in soil collected from woodland garlic mustard infestations to plants grown in woodland soil lacking garlic mustard. Wilcoxon Signed-Rank tests indicate that white snakeroot growth was positively impacted by soil history, while garlic mustard was not (p = 0.05; p = 0.60, respectively). We conclude that garlic mustard has the potential to alter the function and possibly the composition of the soil microbial communities, while surprisingly increasing the growth of white snakeroot seedlings. Furthermore, it seems that garlic mustard can elicit effects during its first three months of growth, suggesting that this plant should be targeted for removal early during its biennial life-cycle. Future studies should examine these findings in the field.