6. Trillium nivale Riddell, Syn. Fl. West. States. 93. 1835.
Snow trillium, dwarf white trillium
Rhizomes short, praemorse. Scapes usually 1, 6-gonal in cross section, 0.3–0.5 dm at onset of anthesis, expanding to 0.45–0.8 dm, slender, glabrous. Bracts distinctly petiolate; blade bluish green, elliptic-ovate to ovate, 1.5–4.5 cm × 0.7–34 mm, base abruptly rounded to petiole, apex round-obtuse. Flower erect, fragrance sweet; sepals spreading, flat, bluish green, lanceolate, 10–32 × 2–7 mm, shorter than petals, margins entire, apex obtuse; petals very showy, recurved to erect-spreading, white, veins not engraved on adaxial surface, ovate-elliptic to oblong, 1.5–3.5+ × 0.8–1.5 cm, thin- to firm-textured, margins entire to slightly wavy, apex obtuse-acuminate; stamens straight, 5–18 mm; filaments white, slightly shorter than anthers, slender; anthers straight, pale yellow, 2.5–11 mm, thin, dehiscence introrse; ovary greenish white, ± globular, obtusely 3-angled; style with tips spreading, elongate, 0.5–1.5 mm, slender; stigmas prominent, recurved or curled, connate basally, white, linear, threadlike, 4–12+ mm; pedicel erect in anthesis, rapidly recurving below leaves after pollination, 5–20 cm. Fruits greenish white, odorless, globose-ovate, 0.6–1 × 0.5–0.8 cm, pulpy, not juicy. 2n = 10.
Flowering spring (early Mar--early Apr). Forested, limestone-derived soils, alkaline glacial drift or loess, creeping soils at head of ledges, talus of cliff bases, crevices in limestone cliffs, gravelly deposits on higher floodplain riverbanks; 100--300 m; Ill., Ind., Iowa, Ky., Md., Mich., Minn., Mo., Nebr., Ohio, Pa., S.Dak., W.Va., Wis.
Trillium nivale occurs primarily at the southern edge of Pleistocene glaciation and shuns humus, leaf deposits, and much plant competition.