PAPAVERACEAE (poppy family)

Plants annual, biennial, or perennial herbs (shrubs elsewhere), often with white or colored sap. Leaves alternate (often subopposite in Stylophorum; opposite elsewhere) or basal, sessile or short-petiolate. Stipules absent. Leaf blades simple or compound, the blade often 1–4 times pinnately or ternately lobed or dissected (the blade more or less palmately lobed in Stylophorum). Inflorescences terminal (sometimes also axillary in Chelidonium), of solitary flowers or loose clusters (these sometimes appearing as small panicles or umbels), the flowers usually subtended by small bracts. Flowers actinomorphic, hypogynous (the receptacle sometimes expanded and forming a thin, small cup- or saucer-shaped disc below the flower), perfect. Calyces of 2 or 3 sepals, these free or fused to well above the midpoint, similar in size and shape, mostly obovate, shed as the flower opens. Corollas of 4 petals (6 in Argemone, 7–12 in Sanguinaria, numerous in rare forms with doubled corollas), these free, similar in size and shape (somewhat unequal in Sanguinaria), narrowly oblanceolate to obovate, lacking a basal pouch or spur, variously colored. Stamens 12 to numerous, the filaments free, the anthers small, attached at or near the base, usually yellow. Pistil 1, composed of 2–18 carpels, the ovary superior, 1-locular or appearing 2- to multi-locular by intruding placentae, the placentation parietal. Style 1 per flower or absent, when present unbranched, the stigmas or stigma lobes as many as the carpels, variously shaped, sometimes persistent at fruiting. Ovules numerous. Fruits capsules that are dehiscent longitudinally by valves or by pores near the tip (circumscissile or breaking into indehiscent 1-seeded segments elsewhere), usually with numerous seeds. Seeds small, variously shaped, the embryo curved, the surface dark brown to black, sometimes with a pale aril or elaiosome (oil-bearing aril-like appendage attractive to ants). About 23 genera, about 230 species, nearly worldwide, most diverse in north-temperate regions.

The Papaveraceae are sometimes circumscribed broadly to include the genera here treated in the closely related Fumariaceae. For further discussion, see the treatment of that family.

Numerous members of the family are cultivated as ornamentals and many have a long history of medicinal use (see treatments of the genera).