Inflorescences interrupted or condensed distally. Fruits (2.3-)2.5-3.5 mm; wing usually 0.2-0.3 mm wide (occasionally fruits almost wingless in some southwestern plants). Flowering late summer-fall. Sand dunes, sandy and gravely shores, sandy waste places, fields; 100-2000 m; Alta., B.C., Man., Ont., Que., Sask.; Ariz., Ark., Calif., Colo., Idaho, Ill., Ind., Kans., Minn., Mo., Mont., Nebr., Nev., N.J., N.Mex., N.Y., N.Dak., Ohio, Okla., Oreg., S.Dak., Tex., Utah, Wash., Wis., Wyo.; n Mexico (Chihuahua); probably Europe (locally introduced and confused with C. nitidum).