This weedy annual is widespread across northeastern states and locally elsewhere (K), especially along railroads and rocky roadsides. The earliest coll. from Ky. appears to be that of E. King #311 from ROWA in 1926 (MDKY). Many new records have been added during recent years by R. Thompson (BEREA). Variation may need further study; two subspecies are recognized in Europe (2n = 14 and 28).