Disturbances may add or remove resources from communities and can facilitate the spread of some invaders. Differential successes of exotic plants to spread into different communities suggest that some habitats are more invasible than others. Hesperis matronalis (dame's rocket) is widespread across the continent and has potential to become a major problem in natural communities owing to its ability to exploit excess resources and its negative effect on native species. We grew H. matronalis seedlings in a Colorado foothill community at various levels of nitrogen and water with and without neighbors. We expected H. matronalis to maximize its growth under high resource conditions especially without neighbors because ruderal species are able to take advantage of excess resources. Our results reveal that presence or absence of neighbors was the main decisive factor for H. matronalis (aboveground biomass and relative growth rate) success, though seedlings particularly suffered under low resource conditions. Early determination of the potential invasiveness of a widespread exotic species such as H. matronalis in natural communities may promote effective management.