Technical Abstract: Breeding efforts will play a critical role in meeting the increasing demand for cellulosic bioenergy feedstocks. However, a major concern is the potential development of novel invasive species that result from breeder’s efforts to improve agronomic traits in a crop. We use reed canarygrass as a case study to evaluate the potential of breeding to give rise to invasive species. Reed canarygrass has been improved by breeders for use as a forage crop, but it is unclear whether breeding efforts have given rise to more vigorous populations of the species. We evaluated cultivars and European and North American wild populations in upland and wetland environments to identify differences in vigor between the groups of populations. While cultivars were among the most vigorous populations in an agricultural environment (uplands with nitrogen addition), there were European wild populations as vigorous in uplands and no differences in above or belowground production between any populations in wetland environments. These results suggest that breeding has only marginally increased vigor in upland environments, and that these gains are not maintained in wetland environments. Breeding often selects improvements for a specific target population of environments, and stability across a wide range of environments has proved elusive for even the most intensively bred crops. We conclude that breeding efforts are not responsible for wetland invasion by reed canarygrass and offer guidelines that will help reduce the possibility of breeding programs releasing cultivars that will become invasive.