This annual is widespread on xeric base-rich soils in eastern North America, but uncommon to rare on siliceous soils of the southeast (FNA 25, K). It is close to neglectus; see notes under that name. Some colls. from Ky. are hard to assign, especially if lemmas are only 2-3 mm long (e.g. from FAYE and SIMP at KY). Some colls. (e.g. from BULL at KY and MEAD at US) have pilose leaves, and may approach the more western var. ozarkanus (Fern.) Shinners. However, their spikelets do not indicate ozarkanus (FNA 25, W), which are reported to be generally smaller than in vaginiflorus, but with glumes longer than lemmas (versus shorter); at least faintly 3-nerved lemmas (versus 1-3 nerved); and obtuse paleas (versus acute to acuminate). No records of ozarkanus from Ky. are accepted here, although it has been reported by Cr, R. McGregor (in annotations) and others. The occurrence of ozarkanus east of the Mississippi Rv., as a variety or species, remains somewhat uncertain, given that it can appear intermediate between neglectus and vaginiflorus in some characters.Treatments of these taxa have varied greatly (St, Y, FNA 25, W). With some biogeographic parallels, cryptic variants may also exist within associated xerophytic calciphiles in Sedum, Mononeuria, Cerastium, Houstonia, Rudbeckia and Allium.