As traditionally circumscribed (Clayton and Renvoize, 1986), a genus of about 300 species, nearly worldwide.

By Barkworth’s (1990, 1993) narrower definition, Stipa is excluded from the North American native flora. According to her analysis (Barkworth 1990), Stipa in the broad sense consists of a number of groups best treated as separate genera that may be classified into at least four major lineages. She treated the Missouri taxon as one of five species in the North American endemic genus, Hesperostipa (Elias) Barkworth, which previously had been classified as a section of Stipa.