Description from Flora of China
Callista clavata Kuntze; Dendrobium aurantiacum H. G. Reichenbach var. denneanum (Kerr) Z. H. Tsi; D. clavatum Wallich ex Lindley (1852), not Roxburgh (1832).
Stems robust, to 47 cm, more than 4 mm in diam. Leaves oblanceolate, to 11 × 1.8-4.5 cm. Inflorescences subapical on leafless penultimate and older stems, stiffly arching, 5-14 cm, to 7-flowered; floral bracts prominent, 1.8-3 cm. Flowers ca. 5 cm wide, orange-yellow, lip with a maroon center or large purple spots on adaxial surface; many clones ± cleistogamous.
Epiphytic on tree trunks in open forests; 600-2500 m. W Guangxi, S Guizhou, Hainan (Bawangling), NW to SE Yunnan [India, Laos, Myanmar, Nepal, Thailand, Vietnam].