This widespread tetraploid (2n = 40) of warm temperate to tropical regions extends up the Mississippi Valley to a somewhat disjunct cluster of records in w. Ky. and adjacent Stewart Co., Tenn. (Cr, Ch, FNA 25). There is also a disjunct cluster of largely pre-1950 records in the Tennessee Valley around Knoxville (Ch; E. Wofford, pers. comm.). Although sometimes found in farmland, its more natural habitats include sandbars along larger medium-sized streams. P. boscianum is easily overlooked. Differences from similar species (especially pubiflorum) include its annual habit (versus perennial), and its dark brown fertile lemmas at maturity (versus stramineous or pale brown), with obovate to orbicular shape (versus variously shaped).