Herbs , annual, biennial, or perennial, scapose or caulescent, from taproots; sap white, orange, or red. Stems when present leafy. Leaves: basal rosulate, petiolate; cauline alternate, proximal leaves petiolate, distal subsessile or sessile, sometimes clasping (in P . somniferum ); blade unlobed or 1-3× pinnately lobed or parted; margins entire or toothed, scalloped, or incised. Inflorescences cymiform, with flowers disposed in 1s, 2s or 3s on long scapes or peduncles; bracts present; buds nodding [erect]. Flowers: sepals 2(-3), distinct; petals 4(-6); stamens many; pistil 3-18[-22]-carpellate; ovary 1-locular, sometimes incompletely multilocular by placental intrusion; style absent; stigmas 3-18[-22], radiating on sessile, ± lobed disc, velvety. Capsules erect, 3-18[-22]-pored or short-valved immediately beneath persistent or sometimes deciduous (in P . hybridum ) stigmatic disc. Seeds many, minutely pitted, aril absent. x = 7. Papaver is rich in alkaloids, notably opiates. The genus is quite complex cytologically; in addition to diploids, there are numerous polyploid species and some that apparently are aneuploid. Most commonly, n = 7 or a multiple, and 2 n ranges from 14 to over 100. There are published chromosome counts for almost every taxon in the flora, but for the introduced species none has been made from wild-collected North American material. The scapose poppies in the flora are native; the caulescent ones, except Papaver californicum , are introduced Eurasian ornamentals, crop weeds, and ballast waifs. All the scapose species are confined to arctic and alpine habitats. Plants of the introduced caulescent species, especially P . rhoeas , P . dubium , and P . somniferum , vary greatly in size, and surprisingly diminutive mature individuals are sometimes found, especially northward.
Sep 2; pet normally 4, white or colored, our spp. never yellow; ovary of 4-many carpels, the placentas deeply intruded as partial partitions; stigmas as many as the carpels, sessile and radiating on a disk terminating the ovary; fr opening by small valves just below the margin of the stigmatic disk; seeds not arillate; herbs with milky or colored juice and large, usually long-peduncled fls terminating the stem and branches. 100, cosmop.
Three cult. spp. that occasionally escape in our range are included in the key but not described
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.