天麻 tian ma

Gastrodia elata f. alba S. Chow; G. elata f. flavida S. Chow; G. elata f. glauca S. Chow; G. elata var. gracilis Pampanini; G. elata f. pilifera Tuyama; G. elata f. viridis (Makino) Makino; G. elata var. viridis (Makino) Makino; G. mairei Schlechter; G. viridis Makino.

Plants 30-100 cm, rarely to 200 cm tall. Rhizomes usually ellipsoid, 8-12 cm, stout, 3-5(-7) cm in diam., sometimes larger, fleshy, densely noded, with triangular or broadly ovate scales at nodes. Peduncle orange, yellow, grayish brown, or greenish, 25-80(-150) cm, with several membranous sheaths toward base; rachis 5-30(-50) cm, subdensely to densely 20-50-flowered; floral bracts oblong-lanceolate, 10-16 mm, often exceeding ovary, membranous, apex acuminate. Flowers suberect, resupinate, opening weakly, orange, pale yellow, bluish green, or yellowish white; pedicel and ovary 7-12 mm. Perianth tube urceolate, 8-10 × 5-7 mm, with a deep sinus between lateral sepals, base inflated, outer surface smooth; free portion of sepals ovate-triangular, 3-5 mm, apex obtuse; free portion of petals suboblong, smaller than sepal lobes, apex acute; lip obscurely 3-lobed, oblong-ovoid, 6-7 × 3-4 mm, glabrous, base clawed, apical margin irregularly fimbriate; claw with a pair of gibbous foldings; disk papillose, with a pair of fleshy reniform calli. Column 5-7 mm; column foot short. Capsule obovoid-ellipsoid, 14-18 × 8-9 mm. Fl. and fr. May-Jul. 2n = 24, 30, 36.

Sparse forests, open places in forests, forest margins, thicket margins; 400-3200 m. Anhui, N Fujian, Gansu, Guizhou, Hebei, Henan, Hubei, Hunan, Jiangsu, Jiangxi, Jilin, Liaoning, Nei Mongol, Shaanxi, Shanxi, Sichuan, Taiwan, Xizang, Yunnan, Zhejiang [Bhutan, NE India, Japan, Korea, Nepal, Russia (Far East)].

This species is widely cultivated for its tubers (tianma) that are used in traditional Chinese medicine for the treatment of convulsive disorders such as epilepsy.