Sp. Pl. 1: 541. 1753.
Aerial shoots 5-30 cm, from rhizomes, rhizomes primarily horizontal. Basal leaves 0-1, ternate; petiole 4-25 cm; terminal leaflet ± sessile, rhombic to oblanceolate or obliquely oblanceolate, 1-4.5 × 1.4-3.7 cm, base narrowly cuneate, margins crenate-serrate, serrate, occasionally dentate or incised on distal 1/3-1/2, apex acuminate to obtuse, surfaces glabrous or puberulous to pilose; lateral leaflets unlobed or 1×-lobed or parted; ultimate lobes 4-15 mm wide. Inflorescences 1-flowered; peduncle puberulous, villous, or glabrous; involucral-bracts 3, 1-tiered, ternate, ±similar to basal leaves, bases distinct; terminal leaflet petiolulate or sessile, rhombic to oblanceolate or obliquely oblanceolate, 1-5 (-5.5) × 0.5-3 cm, base narrowly cuneate, margins crenate to serrate, serrate to dentate, occasionally incised on distal 1/3-1/2, apex acuminate to acute, surfaces glabrous or puberulous to pilose; lateral leaflets unlobed or 1×-lobed or parted, ultimate lobes 5-20 mm wide. Flowers: sepals (4-) 5 (-6), white, rarely pink, or abaxially white or tinged pink or blue and adaxially white, oblong to ovate, 6-25 × 4-8 mm, glabrous; stamens 30-60. Heads of achenes spheric or nearly so; pedicel 1-6 (-8) cm. Achenes: body ellipsoid or ovoid, 2.5-4.5 × 1-1.5 mm, not winged, puberulous or villous; beak straight to curved, rarely recurved, 0.5-2 mm, ±glabrous to sparsely puberulous, not plumose.
Alta., Man., N.B., N.S., Ont., Que., Sask., Ala., Conn., D.C., Del., Ga., Ill., Ind., Iowa, Ky., Maine, Mass., Md., Mich., Minn., Mo., N.C., N.Dak., N.H., N.J., N.Y., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Va., Vt., W.Va., Wis.
Varieties 2 (2 in the flora).
Anemone quinquefolia and its relatives (A. grayi, A. lancifolia, A. lyallii, A. oregana, and A. piperi) are remarkably similar morphologically. Consideration of the sizes of various plant parts, degree of lobing of lateral leaflets, and orientation of the rhizome are particularly critical in distinguishing these species. This species complex also shares close morphologic affinities with both European (e.g., A. nemorosa Linnaeus) and Asian (e.g., A. altaica Fischer ex Ledebour) plants.
"broadened" is not a number.