This annual weed is widespread across temperate North America. It was unknown in Ky. until about 1900. In 1914 Gm noted: "sometimes observed along railroads and elsewhere." B. tectorum has now become locally abundant across the state; it remains closely associated with railroads and larger roadsides. Colls. from CAMP (KNK), HICK (MUR) and elsewhere are referable to var. hirsutus Regel, but that taxon is not recognized in recent treatments.