Native diploid, tetraploid, and hexaploid populations of Atriplex canescens were surveyed in southern New Mexico and west Texas. Female to male ratios were approximately equal in diploid populations and female-biased in tetraploid and hexaploid populations. Tetraploids in New Mexico and Texas differed from northern populations with more male and fewer monoecious plants. Hexaploids appeared to have slightly fewer female plants than tetraploids during flowering, but during the winter there were 6%-20% more seed-bearing plants because of the high frequency of monoecious plants. The three cytotype populations generally fited expected ratios using an X, Y sex-determining model. Monoecious diploid plants cannot be explained by the genetic model. Two types of monoecious expressions were observed, and possible genetic mechanisms are discussed.