Description from Flora of China
Platanthera marginata (Colebrooke) Lindley.
Plants 8-37 cm tall. Tubers ellipsoid or narrowly ellipsoid, 2-4 × 1-2.5 cm, fleshy. Stem erect, terete, glabrous, with 1 or 2 tubular sheaths at base, 3-5 leaves below middle, and 3-5 bractlike leaves above. Leaf blade narrowly oblong or oblong-lanceolate, 4-9 × 1-2 cm, base contracted into amplexicaul sheath, margin yellow when dried, apex acuminate or subobtuse. Raceme 3-15-flowered, 2.5-10 cm; floral bracts lanceolate, apex long acuminate; ovary twisted, arching, cylindric-fusiform, including pedicel 8-13 mm. Sepals green, petals and lip yellow. Dorsal sepal forming a hood with petals, erect, cordate or broadly ovate, concave, 7-7.5 × 5-6 mm, 3-veined, apex acute; lateral sepals reflexed, obliquely ovate or narrowly ovate-oblong, 7.5-8.5 × 2.5-3.5 mm, 3-veined, apex acute. Petals obliquely ovate-triangular, 6.5-7.3 × 3-3.8 mm, 2-veined, apex acute; lip spreading, 11-13 mm, deeply 3-lobed above base; lateral lobes spreading at acute angles to mid-lobe, linear or linear-lanceolate, 7-8 × 1-1.4 mm; mid-lobe ligulate, 8-9 × 2-2.3 mm; spur pendulous, clavate, 8-13 mm, apical half dilated and 1.5-2 mm in diam.; stigmas falcate, long. Fl. Oct-Nov. 2n = 42.
Forests, grasslands at forest margins; 500-1200 m. S Yunnan [Bhutan, India, Kashmir, Myanmar, Nepal, Thailand].