Description from Flora of China
Dendrobium odiosum Finet.
Stems erect, cylindric or sometimes with several nodes dilated and fusiform above base, to 80 cm, 2-20 mm in diam., rigid, usually branching, internodes to 4.7 cm, with longitudinal channels or stripes, deep yellow or orange when dry, glossy. Leaves often 3-6, alternate on main stem and upper part of branches, linear, 2.5-7 × 0.3-0.6(or more) cm, with leathery sheaths at base, apex obtuse and unequally bilobed. Inflorescence 1-2.5 cm, 1- or 2-flowered raceme; peduncle 5-10 mm; floral bracts ovate, ca. 2 mm, membranous, apex acute. Pedicel and ovary pale yellowish green, 12-15 mm; ovary slightly dilated; many clones ± cleistogamous. Normal flowers slightly fragrant, spreading, thickly textured; sepals and petals golden yellow, lip golden yellow, lateral lobes with a few red striations inside, disk often pale green. Dorsal sepal ovate-elliptic, (10-)18-24 × (3.5-)5-8 mm, 7-veined, apex acute; lateral sepals ovate-lanceolate, ca. as long as dorsal sepal, but slightly narrower, 7-veined, apex acute; mentum broadly conic, ca. 5 mm. Petals obliquely obovate or subelliptic, ca. as long as dorsal sepal and broader, 7-veined, apex acute; lip 10-20 mm long and wide, with a basal callus, middle 3-lobed; lateral lobes embracing column, ± subrounded, apex rounded; mid-lobe suboblate or ensiform-rounded, acute; disk with short, dense papillae between lateral lobes and extending to mid-lobe. Column ca. 5 mm, base slightly dilated, foot ca. 6 mm; column teeth subtriangular, apex short and obtuse; anther cap obliquely conic, surface smooth, front with 3 ridges, front margin denticulate.
One of us (H. P. Wood, Dendrobiums, 638. 2006) has noted that the sectional placement of Dendrobium hancockii remains unclear. In addition, two entities are being offered as D. hancockii in the horticultural trade, both often mislabeled "D. hainanense." One, true D. hancockii, has leaves linear, retuse, ca. 3 cm × 3 mm; petals clavate; and lip inrolled with clear lateral lobes. The other, an undescribed taxon, has leaves lanceolate, ca. 15 cm × 3 mm; sepals and petals narrower and pointed; and lip flat, cordate, with lateral lobes indistinct.
Gary Yong Gee noted (pers. comm. to Li Bing Zhang in Nov. 2017): Dendrobium odiosum might be best treated as a separate species from D. hancockii. D. hancockii has leaves longer than 7 cm, dorsal sepal triangular, pointed petals narrower and lip mid-lobe tapering, while D. odiosum has leaves shorter than 3 cm, dorsal sepal elliptic, petals shorter and with rounded apices, and lip mid-lobe with broad rounded apex.
Epiphytic on tree trunks in mountain forests, lithophytic on rocks in mountain valleys; 700-1500 m. S Gansu, NW Guangxi, S Guizhou, Henan, SE Hubei, SE Hunan, Shaanxi, S Sichuan, NE and SE Yunnan [N Vietnam].