Ten naturalized populations of tall wheatgrass (Thinopyrum ponticum) were evaluated in a completely randomized block design with three replicates. Each plant was analyzed for morphological and reproductive characters, and statistical and genetic characters were estimated. Significant differences (p < 0.001) were obtained for the means of all ten populations, indicating great variability between tall wheatgrass populations. The results show that the environmental coefficients of variation were high for total seed production (69.24%), number of tillers (54.93%), number of spikes (48.50%), and dry matter production (49.01%). Coefficients of variation were rather low for spike length (19.11%) and the 1000-seed weight (18.44%). Heritability was high for seed weight (0.86), dry matter production (0.55), and the number of tillers (0.55). Intermediate heritability was found for total seed production (0.30), and low heritability for the number (0.19) and length (0.09) of spikes. Even though the number of spikes showed an intermediate heritability, it was highly and positively correlated with seed production (r=0.603), and a little less so with seed weight (r=0.177). Seed weight showed a high heritability and was positively correlated with seed production (r=0.285). The wide variability observed between populations for almost all the studied characters will allow them to be integrated into a single germoplasm or into a genetic pool that could be used in programs aimed at the genetic improvement of tall wheatgrass.