Dendrobium mirbelianum

Dendrobium mirbelianum Gaudich., in Freyc., Voy. Uranie, Bot. (1826) 423.

Type: Gaudichaud s.n. (Moluccas) (holo P).

An erect epiphytic herb. Stems 0.5-3.2 m tall, 1.5-3 cm diam., cane-like, swollen somewhat in basal half and at base. Leaves coriaceous, oblong-elliptic to elliptic-ovate, obtuse or rounded at obliquely bilobed apex, 8-12.5 by 2.5-5.4 cm, articulated to tubular sheaths up to 3.2 cm long. Inflorescences suberect to spreading, 12-45 cm long, 4-30-flowered; peduncle usually longer than rachis; bracts deltoid to elliptic, acute, 3-7 mm long. Flowers occasionally cleistogamous (especially in Australia and southern New Guinea); pedicel and ovary 1-2.5 cm long. Dorsal sepal erect, linear-lanceolate, acute or apiculate, 2.2-2.8 by 0.6 cm; lateral sepals spreading, obliquely lanceolate to linear-lanceolate, acute 2.4-2.8 by 0.6-0.7 cm; mentum obliquely shortly conical 7-8 mm long. Petals spathulate, acute to subacute, 2.2-5 by 0.4-0.7 cm, not twisted or half-twisted. Lip 3-lobed, 1.6-2.5 (- 3.8) by 1.2-1.5 cm; side-lobes elliptic, rounded in front, erose on margins; midlobe recurved, ovate, acute, c. half length of lip, 0.9-1.5 cm long, margins erose and undulate; callus of 5 erose ridges, central ridge longest and slightly dilated towards apex on middle of midlobe. Column 4-5 mm long, denticulate at apex.
(after Cribb, 1986).

Colours: Leaf sheaths often purple-striped. Flowers greenish-yellow to olive-brown, veined with purple-brown on lip; callus white marked with purple or violet.

Habitat: Epiphyte on trees along the coast, in coastal forest, mangroves and swamp forest, also in rainforest and lithophytic in savannah. Altitude 0 to 650 m.

Flowering time in the wild: Throughout the year, peaking in the dry season (fide O'Byrne).

Distribution: Moluccas, New Guinea, the Bismarck Archipelago, NE Australia (Queensland), and the Solomon Islands.

Distribution: Papua and Papua New Guinea, widespread along the coasts.

Map: MIRBEMAP.JPG [Dendrobium mirbelianum Gaudich., distribution map, redrawn from P. Cribb, Kew Bull. 41 (1986) 644, map 4, with new records added.]

Notes: Dendrobium mirbelianum is a widespread and variable orchid particularly in flower size. It is closely related to the Moluccan Dendrobium calophyllum and possibly also to Dendrobium tokai from Fiji and Tonga but can be distinguished by its ochre or brownish-yellow sepals and petals and lip with broad side-lobes and an ovate-elliptic acute midlobe half the length of the lip. The callus ridges on the lip are scarcely raised towards the apex and taper out on the apical half of the midlobe.

The synonymy of Dendrobium mirbelianum has been discussed in detail by P.J.Cribb & Blaxell (1983). The large-flowered forms from northern New Guinea were described by Schlechter in 1912 as Dendrobium buluense but the flowers are structurally similar to the type of Dendrobium mirbelianum and not specifically distinct. In Australia and southern New Guinea, it usually has small flowers which are often self-pollinating.

This species is frequently seen in cultivation, often mislabelled as Dendrobium schulleri.
(after Cribb, 1986).

Cultivation: Warm growing epiphyte, prefers light position.