Ditichilis spicata is a highly productive salt-tolerant grass species with considerable potential for domestication as a forage crop on saline soils. It is broadly distributed throughout North America in a variety of coastal and inland habitats. Effective efforts to domesticate De spicata will require an ability to predict its primary production under a range of environmental and cultural practices to which it might be subjected Ecotypic differences among populations from contrasting environments might make it necessary to match the physiological adaptations selected in particular natural environments with the environments and culture conditions under which it might be grown. Two coastal and two inland populations were evaluated for differential response to salinity level and temperature. Ecotypic variations with regard to growth, photosynthetic ability, biomass allocation and leaf chemical composition were found. Populations were also found to differ in their responses to the principal anion in the growth substrate. Modeling of photosynthetic response to growth salinity, temperature and light revealed the manner in which these variables influence productive capacity. Studies of the influence of mycorrhizae on growth and physiological function indicated that they are not essential to the abilitY of D. spicata to tolerate salinity.