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Plant population persistence throughout the Great Plains, especially of perennial grasses, is dependent on tiller recruitment from the belowground bud bank. In the northern mixed-grass prairie of the Great Plains, plant communities often include the native rhizomatous grass Pascopyrum smithii (western wheatgrass) but are increasingly invaded by the non-native rhizomatous grass Bromus inermis (smooth brome). Differential bud outgrowth responses of these species to temperature, soil moisture and clipping could alter their competitive interactions and impact native grassland resiliency to climate change. Bud outgrowth from tillers of both species was evaluated under three spring temperature regimes (Average: 12�C 18�C and 24�C) and two soil moistures (short-term drought and well-watered) in a series of two-week growth chamber experiments. The response of western wheatgrass bud outgrowth to clipping was also examined. Smooth brome had more buds per tiller and initiated a greater proportion of these buds than western wheatgrass under all temperature and moisture conditions. Western wheatgrass bud development was reduced at 24�C. Short-term drought did not significantly impact bud outgrowth of either species. Clipping increased western wheatgrass bud mortality and reduced its bud development. The robust vegetative reproductive capacity of smooth brome under a range of environmental conditions is a key mechanism enabling the expansion of smooth brome into northern mixed-grass prairie in North America. Because of the negative impact of clipping on western wheatgrass bud outgrowth, mixed-grass prairie dominated by western wheatgrass may require longer recovery times, especially in areas susceptible to smooth brome invasion. Resiliency of mixed-grass prairie to the separate and interactive effects of climate change, non-native perennial grass invasions, and repeated defoliation depends upon successful tiller recruitment and establishment of native perennial grasses via the bud bank.