Herbs , annual, or perennial from stout rhizomes. Leaves basal and cauline (cauline often absent at flowering time), proximal leaves petiolate, distal leaves sessile; cauline leaves alternate. Leaf blade 1-3-pinnately dissected, segments narrowly linear, margins entire or with occasional tooth. Inflorescences terminal, flowers solitary; bracts absent. Flowers bisexual, radially symmetric; sepals not persistent in fruit, 5(-8), nearly colorless or green, plane, obovate, 6-22 mm, apex ± erose; petals 3-20, distinct, yellow to red [white], often striped or basally darkened with black, purple, or blue, plane, oblanceolate, 8-35 mm; nectary absent; stamens 15-80; filaments filiform; staminodes absent between stamens and pistils; pistils ca. 20-50, simple; ovule 1 per pistil; style present. Fruits achenes, aggregate, sessile, nearly globose, sides veined or rugose; beak terminal, straight or strongly curved, 0.5-1 mm. x =8. Several species of Adonis are frequently cultivated in North America for their showy flowers. In eastern North America the species sometimes escape from cultivation; although they may become briefly naturalized, most populations evidently do not persist. In the western United States A . aestivalis apparently was introduced as a contaminant in agricultural seed and might have escaped from cultivation. It has become naturalized, and populations tend to persist. Reliance on herbarium specimens, rather than population studies, of annual Adonis in North America has resulted in confused species concepts. Flower color is variable within the species and changes with drying, and diagnostic features of the fruit are reliable only when achenes are fully mature (C. C. Heyn and B. Pazy 1989).
While most Ranunculaceae attract pollinators to often highly specialized floral nectaries, Adonis lacks nectaries, instead offering pollen as a reward. The fruits are harvested by ants.
Leaves and roots are said to be poisonous to humans and livestock.
Much like Ranunculus, but without the nectariferous scale or pit at the base of the pet; cauline lvs alternate, sessile or nearly so, dissected into numerous narrowly linear segments; fls solitary, terminating the stem or its branches; sep 5, green, shorter than the 5-20 conspicuous pet; ovule and seed suspended. 20, temp. Eurasia.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.