This variable weed is widespread across northern and western states but rare to absent in the southeast; 2n = 18 to 108 (FNA 25). It is easily confused with viridis, but has distinctly tapering spikes and retrorsely scabrous bristles. In Ky. the only verified colls. may be from FAYE and WOOD (mostly at KY-Agr. Sch.). In 1914 Gm noted: "frequent in cultivated ground, but not so often seen as [S. pumila]." Anderson (1924) listed colls. dated 1833 to 1919, only from Lexington (FAYE).