[Wikipedia] Eurasia Native, Weed, Habitat, Flower Color: It is native to Eurasia, but it can be found throughout much of the temperate world as an introduced species and sometimes a common weed. For example, it has been noted as a weed in the western United States. It often appears in arable fields, sandy tracks, pits, and docks. It produces yellow flowers May?July that fade to white with four small petals about 1.5 - 3 mm long. (link added by Mary Ann Machi)