Dendrobium constrictum J.J.Sm., Bull. Dép. Agric. Indes Néerl. 19 (1908) 15; Nova Guinea 8, 1 (1909) 79, t. 27, fig. 87; Nova Guinea 8, 3 (1911).
Type: Versteeg 1509 (iso L, as 1509 A).
Rhizome short, creeping, strongly branching. Stems 0.5-1.3 cm apart, 2-3-leaved at apex, cylindrical, the shorter ones fusiform, 2.5-9 cm long. Leaf sheaths tubular, black-punctate. Leaves lanceolate, 3-12 by 1.1-2 cm, apex obtusely bidentate. Inflorescences arising laterally from the leafless stems, racemose, short; rachis 1.5-2 cm long, thick, many-flowered. Floral bracts widely patent, broadly ovate-triangular, 0.4 by 0.3 cm, acuminate, concave, papillose, outside black-punctate, fleshy, 3-nerved. Pedicel and ovary 1 cm long, 6-grooved, minutely punctate. Flowers 1.3 cm long. Dorsal sepal oblong- to lanceolate-ovate, 0.58-0.67 cm by 2.5 mm, 3-nerved, apex conduplicate-acuminate, sharply acute. Lateral sepals obliquely triangular, 0.65 cm by 0.9 mm, apex subulate-acuminate; concave, obtusely keeled, outside near the apex papillose, 4-nerved; mentum oblong-conical, 0.6 cm long, obtuse, appressed to the ovary, front margins connate for 2 mm. Petals elliptic- to lanceolate-ovate, 0.43-0.54 cm by 2-2.4 mm, concave, 3-nerved, margins ciliate to weakly ciliolate, except at base, apex obtuse to acute. Lip constricted a little below the middle, divided into a hypochile and an epichile, longitudinally grooved outside, 1.1-1.3 cm long, base shortly saccate-adnate to the column-foot, with a transverse thickening at the constriction, hypochile elliptic, 0.5-0.6 by 0.3 mm, concave, epichile elliptic, 0.6-0.7 by 0.35-0.4 cm, in upper part more or less fimbriate-ciliolate, apex obtuse to acutely acuminate. Column slightly recurved, dorsally compressed, 0.25 cm long, clinandrium with two large obliquely truncate auricles, stigma semiorbicular to obovate; column-foot linear, 0.7 cm long, parallel to the ovary, fleshy, convex inside, concave outside, near the apex with a subelliptic cavity. Anther cucullate, flat and quadrangular in front, apex truncate, puberulous. Pollinia 4, united into two obovoid bodies.
(after Smith, 1911).
Colours: Sepals greenish white, lip green except for the white apex. Column green, apex white, anther green, pollinia greenish grey.
Habitat: Epiphyte in lowland forest. Altitude 0 to 1200 m.
Flowering time in the wild: June-November.
Distribution: New Guinea, Bismarck Archipelago.
Distribution in New Guinea: Papua (Jayapura and Merauke Regencies); Papua New Guinea (Morobe and West New Britain Provinces).
Notes: Dendrobium constrictum is very similar to Dendrobium capituliflorum, with which it should be compared.
Cultivation: Warm growing epiphyte.