Sp. Pl. 1: 508. 1753.
Plants to 15 dm, glabrate, glaucous. Stems simple or branching. Leaves to 30 cm; blade sometimes sparsely setose abaxially on midrib; margins usually shallowly to deeply toothed. Inflorescences: peduncle often sparsely setose. Flowers: petals white, pink, red, or purple, often with dark or pale basal spot, to 6 cm; anthers pale yellow; stigmas 5-18, disc ± flat. Capsules stipitate, subglobose, not ribbed, to 9 cm, glaucous.
Phenology: Flowering spring–summer.
Habitat: Fields, clearings, stream banks, railroads, roadsides, and other disturbed sites
Elevation: 0-1300 m
Introduced; Greenland, Alta., B.C., Man., N.B., Nfld. and Labr. (Nfld.), N.S., Ont., Que., Sask., Ariz., Calif., Conn., Ill., Mass., Maine, Mich., Minn., Mo., N.H., N.J., N.Mex., N.Y., N.C., N.Dak., Ohio, Oreg., Pa., Tex., Utah, Vt., Va., Europe, Asia.
Unknown in the wild, Papaver somniferum probably came originally from southeastern Europe and/or southwestern Asia. It has been cultivated for centuries as the source of opium (and its modern derivatives heroin, morphine, and codeine), and also for edible seeds and oil. Various color forms with laciniate and/or doubled petals are grown for ornament. Widely introduced from cultivation and also as a crop weed, it should be expected elsewhere in the flora.