Dendrobium pentapterum Schltr., in K.Schum. & Lauterb., Nachtr. Fl. Deutsch. Schutzgeb. Südsee (1905) 161; Repert. Spec. Nov. Regni Veg. Beih. 21 (1923) t. 182, fig. 683.
Type: Schlechter 13983 (B, lost; AMES, BM, BR, P); 14434 (B, lost).
Erect tufted epiphyte 6-20 cm high, usually with ascending habit of growth. Roots 0.5-l mm diameter. Rhizome usually short, sometimes new pseudobulbs arising 1-2 nodes up from the base of older stems. Pseudobulbs 1.5-6 by 0.3-0.8 cm, fusiform to ovoid, constricted at nodes, with 1-4 leaves at apex. Leaves 2-9.5 by 0.3-1.1 cm, erect to suberect, linear-elliptic, apex obtuse, mucronate, sometimes slightly unequally bilobed; sheaths smooth, pale green, old sheaths persistent, greyish. Inflorescences terminal, arising from both leafy and leafless stems, 1(-3)-flowered; bracts ovate, apiculate to acuminate. Flowers 2-3.5 cm long, widely opening, lasting several months. Median sepal 8-16 by 4-7 mm, ovate-elliptic, obtuse to subacute, mucronate. Lateral sepals 15-30 by 6-l0 mm, obliquely ovate, obtuse mucronate to acuminate; basal fused part 2-7 mm long, cylindrical to subconical; mentum total length 10-18 mm, tip truncate to obtuse or bilobed. Petals 7-15 by 3-5.5 mm, subspathulate, apiculate. Lip 15-24 by 2.5-4.5 mm, subtrilobate, oblanceolate, adnate to column foot at base, apical part free, margins incurved, without a cross-ridge, apex not recurved, acute to subacuminate. Column 3-4 mm long; foot 10-18 mm long; anther 2-2.5 mm broad; pollinia 1-1.5 mm long. Ovary with 5 main wings and usually several other smaller wings, dorsal wings undulate; pedicel and ovary 17-34 mm long. Fruit (immature) 18 by 7 mm; ovoid.
(after Reeve & Woods, 1989).
Colours: Roots white with green tips. Sepals and petals pale greenish white to creamy-yellow, lip greenish with bright orange to orange-red apex; ovary greenish.
Habitat: Epiphyte in montane forest. Altitude 800 to 2000 m.
Flowering time in the wild: April, September, November, December.
Distribution: The Philippines, New Guinea.
Distribution in New Guinea: Papua New Guinea (Sandaun, Western Highlands, Madang and Morobe Provinces).
Map: PENTAMAP.JPG [Dendrobium pentapterum Schltr., distribution map, redrawn from T.M. Reeve & P.J.B. Woods, Notes Roy. Bot. Gard. Edinburgh 46 (1989) 288, map 14 (Philippine record not indicated).]
Notes: Dendrobium pentapterum has a rather limited distribution in NE New Guinea, but surprisingly has recently been recorded from Mt. Apo on Mindanao in the Philippines (Cootes 2001).
Claims have been made by Mansfeld (1929) and P.Royen (1980) that this species occurs in the alpine zone. Keysser 92 (cited by Mansfeld) is now not available, but it should be noted that many of the altitudinal data given by Keysser (as cited by Mansfeld) are extremely doubtful, being generally far to high for the species indicated (obs. Schuiteman & de Vogel). Brass 10529 (cited by van Royen) from near Lake Habbema in West New Guinea, has been examined and is a typical specimen of Dendrobium vexillarius.
Dendrobium pentapterum is most closely allied to Dendrobium nebularum and the differences between these two are noted under that species.
Despite its limited distribution Dendrobium pentapterum is often locally abundant. Schlechter (1912) records that 'on a single tree a hundred or more specimens may be seen together'. This feature is also reported for parts of the Jimmi Valley in the Western Highland Province.
Of all the larger-flowered tufted 'Oxyglossum' species Dendrobium pentapterum is the only one commonly with single-flowered inflorescences. The flowers are widely opening, long lasting.
(largely after Reeve & Woods, 1989).
Cultivation: Intermediate growing epiphyte.