In North America, this annual weed occurs mostly in mid-temperate zones of eastern and western states (FNA 24, K). Otherwise, its ecology is similar to the closely related species, tectorum, which is much more common. B. sterilis was not recorded in Ky. until the 1930s (B). It has distinctively larger spikelet parts, and it tends to be more robust overall; 2n = 14 and 28 (versus only 14 in tectorum). B. diandrus Roth has even larger lemmas than sterilis, and may also be expected as a waif in southeastern states; 2n = 42 and 56 (Y, FNA 24). It has not been verified in Ky., but a coll. of sterilis was misidentified by Gunn (1968b) as B. rigidus Roth, which has often been included within diandrus (M).