This annual is widespread across most of North America, but it is local, rare or absent in southeastern states (K, W). In Ky. and Tenn., most records are from gravely or sandy riverbanks west of the Appalachians. Most central Appalachian records are from the Kanawha Rv. in W.Va. and the James Rv. in Va. (K, W). See notes under trachysperma, which is not distinguished here.