Stems to 0.5-5.2 dm, base with few petioles (occasionally thatchlike) persisting from previous year. Leaves: basal leaves with petioles to 5-30 cm; cauline leaves 2-5, base scarcely membranous or clasping. Flowers 2.5-5 cm diam.; sepals 5-7(-9), spreading, bright to pale yellow when fresh, ovate to obovate or nearly orbiculate, 10-20 mm; petals 10-15(-25), yellow, 1/2-2/3 length of stamens when pollen shed, 3-6 mm. Follicles usually 5-12, 8-12 mm including beak; beak usually straight or slightly incurved (rarely slightly recurved). 2 n =32. Flowering spring-summer. Calcareous soils (rarely not calcareous) in alkaline meadows and open swamps; 100-500 m; Conn., Del., N.J., N.Y., Pa., Ohio. Trollius laxus is closely related to the widespread, relatively common, western species T . albiflorus . Morphologically, the two are separated only by sepal color and the tendency for T . albiflorus to have slightly recurved follicular beaks and slightly smaller seeds. Trollius laxus has been extirpated from central Pennsylvania. The species has been reported from Michigan; E. G. Voss (1972+, vol. 2) cast doubt on its occurrence there because no specimens to substantiate the reports have been found.
The Cherokee used infusions prepared from the leaves and stems of Trollius laxus to treat thrash (D. E. Moerman 1986).
Stem 1-5 dm; basal lvs long-petioled, cauline 1-3, chiefly above the middle, sessile or subsessile and often approximate; blades subrotund, 3-5-parted with 3-lobed and coarsely toothed, cuneate-obovate segments; sep 5-7, greenish-yellow to bright yellow or cream, elliptic, 15-20 mm, at first incurved-ascending; staminodes oblong, 3-5 mm; follicles 1 cm; 2n=32. Swamps, wet woods and wet meadows; Conn. to Del., Pa., and O. Apr.-June.
Gleason, Henry A. & Cronquist, Arthur J. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. lxxv + 910 pp.