Description from Flora of China
Orchis susannae Linnaeus, Sp. Pl. 2: 939. 1753; Habenaria susannae (Linnaeus) R. Brown; Hemihabenaria susannae (Linnaeus) Finet; Platanthera robusta Lindley; P. susannae (Linnaeus) Lindley.
Plants robust, 45-120 cm tall. Tubers ovoid-cylindric, 3-6 × 1-2.5 cm. Stem stout, with several tubular sheaths at base and several to many leaves intergrading into amplexicaul sterile bracts above. Leaves ovate, oblong, or lanceolate, 6-10(-12) × 3-6 cm, apex acute. Sterile bracts often foliaceous, ovate-elliptic to lanceolate, 4-7 × 1-3.5 cm, apex acuminate. Rachis 6-15 cm, laxly 2-5-flowered; floral bracts foliaceous, lanceolate, 3-5 cm, shorter than, equal to, or slightly exceeding ovary, apex acute to acuminate. Flowers fragrant, white, large; pedicel and ovary 40-60 mm, shallowly winged, glabrous. Dorsal sepal erect, broadly ovate to orbicular, 25-30 × 20-28 mm, apex obtuse-rounded; lateral sepals spreading, broadly ovate, slightly oblique, 25-40 × 12-22 mm, usually slightly longer than dorsal sepal, apex obtuse. Petals linear-lanceolate, 7-12 × ca. 2.5 mm; lip irregularly ovate, 25-40 × 25-44 cm; lateral lobes broad, subflabellate, 16-22 × 18-24 mm, lateral margins entire, apical margin lacerate-fimbriate; mid-lobe linear-oblong, 18-30 × 4-6 mm, slightly fleshy, entire; spur straight to gradually curved forward, 6-13 cm × 3-5 mm, apex acute. Fl. Jul-Sep. 2n = 36, 42, 44.
Forests, grassy slopes, damp places in valleys; 500-2500 m. Fujian, Guangdong, Guangxi, Guizhou, Hainan, Jiangxi, SW Sichuan, Yunnan [Cambodia, India, Indonesia, Laos, Malaysia, Myanmar, Nepal, Thailand, S Vietnam].