Canada Wildrye (Elymus canadensis L.), a cool season C₃ grass native to most of the continental United States, is an important component in conservation and wildlife plantings throughout the Midwest.  We determined the biomass yield, seed production, rust resistance and adaptability of endophyte infected (E+) and non-infected (E-) plants from three different accessions.  Seed from two collection sites in Texas and one from Mexico were used for this study.  Space plant nurseries were established in a Randomized Complete Block Design at two locations in southern Oklahoma during the fall of 2007 and were evaluated for 3 years.  Overall, biomass production, seed yield, and stand survival was significantly higher in E+ plants as a whole.  Yields of biomass and seed between E+ plants were similar within years and across lines at both sites, with the Texas accessions producing slightly more biomass and seed.  Biomass and seed production of E- plants from the Texas accessions were also similar, but significantly higher than E- plants from the Mexico line at both sites.   Some significant differences were noted in yield and seed production between E+ and E- plants within the Texas accessions.  However, the effects of infection were negligible, possibly indicating better adaptability to the study sites by these two lines.   Susceptibility to rust was similar across all accessions and sites regardless of endophyte.  The accession from Mexico benefited significantly from endophyte infection in both biomass and seed yield, and more importantly in the plants ability to survive at both sites.  In conclusion, endophyte infection in Canada Wildrye was a benefit, enhancing growth and promoting the plant’s ability to adapt to different environments.