This abundant weedy annual is widespread across temperate regions of North America. It was not reported froim Ky. until 1919 (Anderson 1924), although Gm may have confused it with squarrosus a decade earlier. See further notes under racemosus and secalinus; for detailed keys see Y and FNA 24. The largely East Asian japonicus and the Central Asian squarrosus are closely related diploids, with "at least some panicle branches as long or longer than the spikelets, sometimes sinuous; panicles nodding" (FNA 24). Also, awns on lemmas are relatively long (on average), arising ca. 1.5-2 mm below lemma apices (versus ca. 1-1.5 mm in most other species of eastern states), and usually divergent near bases.