Dendrobium alaticaulinum P.Royen, Alp. Fl. New Guinea 2 (1979) 328, fig. 113.
Type: NGF (Vandenberg) 39665 (holo CANB; iso L, LAE).
Stems flexuose, more or less fleshy, 5- or 6-winged when dried, glabrous. Leaves thin, spreading in one plant by twisting of basal part, ovate-lanceolate, 13-18 by 2-3 mm, subcaudate-acuminate by the extended midrib, midrib slightly grooved above, crested below, lateral nerves numerous, prominent on either side, margins thin, irregularly coarsely scarious-papillate along entire length but more wavy in lower and more papillate in apical part, underside of midrib coarsely papillate mainly in apical part and wavy to about halfway; sheaths 3-5 mm long, ribbed, glabrous. Inflorescence solitary, 12-15 mm long, 3-8-flowered. Peduncle 4-S mm long. Rachis flexuose, stout. Bracts ovate, boat shaped, 25 by 1-2.5 mm, caudate, slightly clasping the rachis, 5-nerved, glabrous. Pedicels glabrous, 5-6 mm long, 5-ribbed. Ovary glabrous, claviform, 3-4 by 1 mm, slightly curved, 5-ribbed, slightly bullate along median rib. Median sepal glabrous, oblong-elliptic, 5-6 by 1.5-2 mm, shortly subulate-acute, 3-nerved, the nerves somewhat prominent on outside in basal part. Lateral sepals glabrous, ovate, the lower 4-5 mm forming a stout 4-5 mm long, rounded, spur-like mentum, margins in lowest 2.5-3 mm connate to each other, apical part slightly spreading, ovate, 5-7 by 3-3.5 mm, subulate-acute, 4-nerved, midrib slightly crested. Petals oblong-obovate, 4.5-5 by 1.5 mm, acute or acutish, 1-nerved, margin in upper half serrate-papillate. Lip glabrous, 5-nerved, spathulate in outline, 10-11 by 3 mm, obovate in apical half, margins slightly folded inwards, stronger so towards basal half of lip, scarious, papillate in upper half, narrowing into a retrorse, glabrous, transverse septum, claw oblong, boat-shaped. Column stout and short, 3 by 1.5 by 1.5 mm. Stelidia indistinct, scarious. Anther cucullate, 1.5 by 1.5 by 1 mm, truncate and fimbriate at tip, retuse and 2-humped at base. Column-foot 5 mm long, ventricose in frontal part.
(after van Royen, 1979).
Colours: Flowers orange or pink at base, white or pinkish in upper part.
Habitat: Epiphyte in moss forest. Altitude (1500) 2200 to 3170 m.
Flowering time in the wild: February-September.
Distribution: New Guinea (endemic).
Distribution in New Guinea: Papua New Guinea (Enga, Southern and Eastern Highlands, Simbu, Madang, and Milne Bay Provinces).
Notes: Dendrobium alaticaulinum is a common species of sect. Pedilonum in upland Papua New Guinea. It is closely related to Dendrobium calyculimentum, from which it differs mainly in the smaller size of all parts. Compact specimens may be confused with Dendrobium dichaeoides, but in that species the leaves are not articulated with the sheaths, as a result of which the dead leaves remain attached to the stems.
Cultivation: Cool growing epiphyte, keep in shade.