Shared enemies commonly mediate interactions between plant species. Here, I investigated how two guilds of enemies can indirectly affect native plant communities through interactions with an invading plant, Cirsium arvense (Canada thistle). First, I assessed how soil microbes in invaded areas can limit the establishment of native plant species. Microbes from invaded soils reduced germination or growth for three of the eight native plant species surveyed, but did not affect Cirsium, which suggests that soil microbial pathways may benefit Cirsium, potentially facilitating its invasion. Second, in the appendix chapter, I assessed the influence of Cirsium invasion on damage by aboveground insect enemies. I observed inconsistent patterns in insect damage, and very minor effects based on plants association with Cirsium. These results suggest that other ecosystem factors are much more influential on insect damage than Cirsium invasion. Together, these results indicate that soil microbial enemies, but not aboveground insect enemies, may be influential in the invasion of Cirsium arvense.