Technical Abstract: We used an individual plant-based simulation model (ECOTONE) to evaluate the importance of allelopathy and soil texture to the invasion of semiarid grasslands by Acroptilon repens. We also assessed the sensitivity of model results to the negative effects of allelochemicals on recruitment and growth of perennial grasses. The ECOTONE model was parameterized for a shortgrass community in eastern Colorado. Experimental simulations used plots with four soil textures and a range of levels of plant sensitivity to allelochemicals. Simulation results showed that A. repens did not dominate the aboveground biomass unless native species were negatively affected by allelochemicals. At moderate levels of plant sensitivity, A. repens became dominant faster and reached a larger proportion of total biomass on fine- compared to coarse-textured soils. Community composition and rate of A. repens dominance were more affected by the sensitivity of plant growth to allelochemicals than sensitivity of recruitment. Allelopathic interactions were an important component of the invasion dynamics of this perennial invasive weed, and further field investigation is warranted.