This annual is widespread in mid- to cool-temperate regions of North America, often growing on shores of streams but also spreading to drier uplands, roadsides and other disturbed sites; 2n = 54. See also diandrus, a more northern species that is closely related and often confused These two species (in section Vestiti) share the following characters (FNA 23, W): scales with anthocyanic (reddish-brown or purplish) pigmentation; fibrous-rooted annuals. Another species in this section to be expected is the East Asian C. sanguinolentus Vah,, which is a rhizomatous perennial.