Plants to 1.4 m, essentially glabrous. Leaves 4-14, ovate, ovate-elliptic to narrowly lanceolate, 5-20 × 2-7 cm. Inflorescences lax racemes; floral bracts lanceolate to oblong, 7-127 mm. Flowers 2-32, rather showy; sepals greenish to rose-colored with rose-colored to purple veins; lateral sepals 16-24 × 8-9 mm, apex very oblique; petals pale pink to rose-colored to orange with red or purple veins, broadly ovate to ovate-lanceolate, 13-17 × 6-8 mm; lip marked with red or purple, strongly veined, distinctly 3-lobed, constricted at middle into 2 parts, proximal part papillose, calli red, minute, warty, lateral lobes prominent subtriangular wings, distal part linear-oblanceolate to narrowly spatulate-oblanceolate, grooved to tip, 14-20 mm, calli near base, erect, orange or yellow, winglike; column erect, short, stout, with pair of lateral processes, 5-10 × 3 mm; anther green; pollinia 2 pairs, yellow, soft. Capsules ellipsoid, glabrate or sparsely pubescent, 20-25 mm. 2n = 40.
Flowering throughout summer (Mar--Aug). Wet gravelly and sandy stream shores and bars, may occur in riparian willow, box elder, and river birch woodlands or in chaparral, seepages, marshes, wet cliffs, hot springs; 0--3000 m; B.C.; Ariz., Calif., Colo., Idaho, Mont., Nev., N.Mex., Okla., Oreg., S.Dak., Tex., Utah, Wash., Wyo.; Mexico; Asia (China, India, s Japan, Tibet).
Two very distinct color forms of this species have been published: Epipactis gigantea forma rubrifolia P. M. Brown, with deep red stems and leaves, and E. gigantea forma citrina P. M. Brown, with lemon-yellow flowers. Both are known from California.
The occurrence of this wide-ranging species in India and Tibet is based on Epipactis royaleana Lindley ex Royle being given as a synonym in a study of the Monocotyledoneae of Karakorum (W. B. Dickoré 1995) and an embryologic study (S. P. Vij et al. 1999).
FNA 2002, Cronquist et al. 1977, Kearney and Peebles 1969
Duration: Perennial Nativity: Native Lifeform: Forb/Herb General: Glabrous perennial from creeping rhizomes, stems 1 to several, to 1.4 m tall. Leaves: Blades 4-14, lower ovate to ovate elliptic to upper narrowly lanceolate, 5-20 cm long by 2-7 cm wide. Flowers: Secund raceme bearing 2-32 showy resupinate flowers, sepals greenish to rose colored veins, 12-15 mm long, petals similar to sepals but thinner, pale pink to rose colored, broadly ovate to ovate lanceolate 13-17 mm long by 6-8 mm wide, lip marked with red or purple, distinctly 3-lobed, constricted to 2 parts in middle, part near tip papillose, basal portion thickened, yellow with several crests leading into the sac; column 6-8 mm long, broadened above. Fruits: Ellipsoid capsule, 20-25 mm long, glabrate or sparsely pubescent. Ecology: Found in wet soil of seeps, springs, and along streams from 3,000-8,000 ft (914-2438 m); flowers April-July. Notes: The showy flowers, secund inflorescence and generally amazingly beautiful plant give this away. Ethnobotany: Used ceremonially, for general body disease, and for decorations. Etymology: Epipactis is from Greek epipaktis,name used by Theophrastus for plant used to curdle milk, while gigantea means gigantic. Synonyms: None Editor: SBuckley, 2010