Dendrobium conanthum

Dendrobium conanthum Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 550; 21 (1923) t. 185, fig. 695.

Type: Schlechter 19996 (holo B, lost).

An epiphytic herb. Stems 1-3 m tall, up to 3.2 cm diam., cane-like. Leaves coriaceous, oblong, elliptic or ovate-elliptic, unequally bilobed at obtuse or rounded apex, 4-12 by 1.85-5.5 cm, articulated to persistent tubular sheaths 1.5-3.5 cm long. Inflorescences spreading or suberect, 30-66 cm long, rather densely 6-20- or more-flowered; peduncle 10-14 cm long; bracts oblong-triangular to lanceolate, acute, 4-8 mm long. Flowers appearing contorted; pedicel and ovary 2.5-4 cm long. Dorsal sepal reflexed and sometimes spirally twisted, narrowly oblong-lanceolate, obtuse or subacute, 2-2.3 by 0.6-0.8 cm, strongly undulate on margins; lateral sepals reflexed, obliquely oblong-lanceolate, acute, 2.3-2.4 by 1.3-1.5 cm, strongly undulate on margins; mentum broadly conical, prominent, 1-1.3 cm long, decurved at apex. Petals linear-spathulate, acute or obtuse, 2.2-3 by 0.3-0.4 cm, spirally twisted and contorted, with undulate margins. Lip 3-lobed, 2.1-2.35 by 1.3-1.75 cm; side-lobes narrowly elliptic, rounded or obtuse and spreading at apex, with verruculose venation and erose margins; midlobe recurved at apex, ovate, acute, 0.8-0.9 cm long, margin erose; callus of 3 keels, the middle one prominently raised at apex on base of midlobe. Column 4-6 mm long, obscurely denticulate at apex.
(after Cribb, 1986).

Colours: Leaves dark green. Flowers yellow-green to yellow, more or less flushed with red-brown or chocolate brown; lip yellow, veined with (violet-) purple or brown.

Habitat: Epiphyte in rainforest, usually in exposed positions. Altitude: 0-800 m.

Distribution: New Guinea, Admiralty Islands, Bismarck Archipelago, Solomon Islands and Vanuatu.

Distribution in New Guinea: Papua and Papua New Guinea, widespread, but absent from seasonally dry areas in the South.

Map: CONANMAP.JPG [Dendrobium conanthum Schltr., distribution map, redrawn from P. Cribb, Kew Bull. 41 (1986) 629, map 2, with new records added.]

Notes: Dendrobium conanthum is a widespread and variable orchid which has been often confused with Dendrobium discolor because of its similarly coloured and contorted flowers. However it can readily be distinguished by its shorter bracts, petals and sepals which lack undulate-crispate margins and a lip which bears a callus with the central ridge elevated on the larger midlobe and the side-lobes spreading and marked with rugulose ridges at right angles to the veins. The degree of petal twisting and contortion varies but is nearly always present to some degree.

Plants of Dendrobium conanthum are often mistakenly grown as "Dendrobium pseudoconanthum", which is a species known only from Sulawesi and doubtfully in cultivation. Nevertheless, the name "pseudoconanthum" has been used, almost certainly erroneously, in Sanders' List of Orchid Hybrids.
(after Cribb, 1986).

Cultivation: Warm growing epiphyte, prefers light position.