Vanilla siamensis Rolfe ex Downie

Distribution: South Yunnan China and Thailand. Habitat: in Yunnan forest from 900 to 1300 meters altitude. Flower: period for China is August. Stem grows to several meters long, with long internodes, with a root and a leaf at each node. Leaves are loosely arranged, fleshy; blade elliptic, 14–25 × 6–8 (–13) cm, glabrous, base slightly contracted, apex acuminate; petiole robust, 1.5–2.5 cm, broad. Raceme axillary, 7–14 cm, many flowered; floral bracts broadly ovate, 7–8 mm, fleshy; pedicel and ovary ca. 2 cm. Flowers opening ephemerally; sepals and petals yellowish green. Sepals are oblong or narrowly ovate, 3.8–4.5 × ca. 1.2 cm, apex rounded and slightly involute. Petals obovate-oblong, ca. 4 × 1–1.3 cm, thinly textured; lip rhombic-obovate, ca. 4 cm, basal half adnate to both sides of column, ± trumpet-shaped, indistinctly 3-lobed; lateral lobes embracing column; mid-lobe undulate at margin, with fimbriate papillae near apex; disk with a cup-shaped, shortly hairy appendage centrally. Column 2–2.6 cm, villous on central surface.