Description from Flora of China
Herminium constrictum Lindley, Edwards’s Bot. Reg. 18: ad t. 1499. 1832; Habenaria constricta (Lindley) J. D. Hooker; Platanthera constricta (Lindley) Wallich.
Plants robust, (30-)45-77 cm tall. Tubers oblong, 3-4 × 0.8-1.5 cm. Stem with 4-6 tubular sheaths at base, 4-6-leaved. Leaves basal and clustered to somewhat spaced along stem, broadly elliptic, 5-13 × 3.5-6.5 cm, apex acute. Inflorescence 21-42 cm; peduncle cylindric, stout; sterile bracts several, lanceolate, to 30 mm; rachis 5-18 cm, densely many flowered; floral bracts ovate-lanceolate, 9-15 mm, exceeding ovary, apex acuminate. Flowers horizontal; sepals pale brown; petals and lip pure white; ovary 8-10 mm including pedicel. Dorsal sepal forming a hood, concave, 7-9 × 2-3 mm, 1-veined, apex obtuse; lateral sepals spreading, narrowly oblong-lanceolate, oblique, 7-9 × ca. 2.5 mm, 1-veined, margin incurved, apex acute to mucronate. Petals ovate-lanceolate, oblique, 9-11 × 3.5-4 mm, 3- or 4-veined, apex obtuse; lip spreading, oblong-obovate, 9-11 × 4-5 mm, ecallose, base shallowly concave, 3-lobed near middle; lateral lobes diverging at an acute angle from axis of lip, triangular to shortly oblong, slightly falcate, 2.8-5.8 mm, apex acute; mid-lobe 3-5.5 mm, slightly broader than lateral lobes, apex obtuse; spur pendulous, globose, 2-3 mm, apex rounded, neck contracted. Column ca. 1.8 mm; viscidia ovoid; rostellum deltoid, with short arms. Fl. Jun-Aug. 2n = 38, 42.
Scrubby slopes; 1500-2800 m. SW and W Yunnan [Bhutan, Cambodia, India, Myanmar, Nepal, Thailand, Vietnam].