Roadsides, railroads, dumps, gravel pits, gardens, vacant lots, limestone pavements and quarries, shores, occasionally spreading into forests. A European native, first collected in Michigan in 1922 along railroad tracks at Ypsilanti, Washtenaw Co., and now a widespread weed, locally common in some places, such as the calcareous gravels in the vicinity of the Straits of Mackinac.

The principal hairs of the stem are simple and ± strongly retrorse; the lower leaves are often strongly flushed with purple.