This study proposes to examine the spatial spread of two noxious weeds: musk and plumeless thistle. Based on field-collected data, a suite of mathematical models of increasing complexity will be developed to assess the rate of spread of these species under different assumptions about the population structure and the spatial heterogeneity of the landscape. This will allow the assessment of which species and environmental characteristics contribute most to invasive spread. Both these thistles are major noxious weeds in the US. Thus, there will be important management implications of such work. The models will be used to ask several applied questions: Are local control strategies also the best for reducing regional spread? What can reduce the rate of spatial spread of these invaders? Do optimal management strategies for each species differ, and if so, why? This project links concepts in population and community ecology and thereby facilitates integration of different modeling approaches for spatial spread. The empirical work will allow improvement of designs for the measurement of dispersal, in particular long distance dispersal. Importantly, this study will improve our understanding of the applicability of different modeling techniques for assessing spread of invasive organisms.