Herbs , perennial, from short caudices. Leaves basal and cauline, proximal leaves petiolate, distal leaves sessile or nearly so; cauline leaves alternate. Leaf blade deeply palmately divided into (3-)5-7 segments, segments obovate, ± 3-lobed, margins coarsely toothed, often incised. Inflorescences terminal, 1-3[-7]-flowered open cymes or flowers solitary; peduncle 2-30 cm; bracts leaflike, not forming involucre. Flowers bisexual, radially symmetric; sepals not persistent in fruit, (4-)5-9[-30], white to orange-yellow [orange-red or purplish], ± plane [strongly concave and incurved], elliptic, orbiculate, or obovate, sometimes short-clawed, 10-30 mm; petals 5-25, distinct, yellow or orange, plane with cupped base of blade, linear-oblong [ovate], ± clawed, 2-10[-40] mm; nectary within pocketlike base of blade; stamens 20-75; filaments filiform; staminodes absent between stamens and pistils; pistils 5-28[-50], simple; ovules 4-5(-9) per pistil; style present. Fruits follicles, aggregate, sessile, oblong, sides transversely veined; beak terminal, straight, 2-4 mm. Seeds black or dark brown, faceted to angular, dull or lustrous. x =8.
As many as 10 Eurasian species of Trollius have been cultivated in North America as ornamentals. Of these, only T . europaeus Linnaeus has been reported to escape. The species infrequently persists near old dwellings in New Brunswick (B.Boivin 1966; H.Hinds, pers. comm.). Trollius europaeus may be distinguished from all North American species by its globose flowers with strongly incurved sepals (in North American species flowers are shallowly bowl-shaped with sepals ± spreading).
Sep 5 or more, large, petaloid; pet none; staminodes numerous, shorter than the stamens, nectariferous at the base; stamens very numerous; filaments slender; anthers linear; pistils several to many; style subulate; follicles thin-walled; perennial herbs with alternate, palmately cleft lvs and large, solitary, terminal fls. 30, 3 in N. Amer., the others Eurasian.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.