Orchids of New Guinea

Prev Taxon: Genus Dendrobium section Phalaenanthe

Current Genus: Genus Dendrobium section Pleianthe

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Prev Species: Dendrobium dolichocaulon

Dendrobium pleianthum

Dendrobium pleianthum Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 625; 21 (1928) t. 210, fig. 793.

Type: Schlechter 16303 (holo B, lost; iso AMES, E, G, K, L, S, Z).

Synonyms:

Grastidium pleianthum (Schltr.) Brieger, in Schltr., Orchideen, ed. 3, I/A (1981) 653.
Exochanthus pleianthum (Schltr.) M.A.Clem. & D.L.Jones, Orchadian 13 (2002) 496

Rhizome very short, roots elongated, filiform, flexuose, glabrous. Stems crowded, erect to suberect, slightly laterally compressed, unbranched, 90-120 cm by c. 8 mm, many-leaved. Leaf sheaths c. 0.8 cm, entirely covering the stem, shining, with raised veins, minutely rugulose. Leaves erect-patent, lanceolate-linear, 13-20 by 0.8-1.5 cm, apex subacute, unequally bilobulate, coriaceous. Inflorescences arising laterally from the stem, racemose, 0.2-0.4 cm long, sessile, rachis very short, conical, 4-10-flowered. Floral bracts scale-like, minute. Pedicel and ovary 2 cm long, slender, glabrous. Flowers resupinated, c. 2 cm across. Dorsal sepal oblong-lanceolate, 1.1 cm long, apex subacute. Lateral sepals falcate, a little shorter than the dorsal sepal, widened at the base, apex acute; mentum 0.3 cm long, obtuse. Petals obliquely linear-ligulate, slightly narrowed to the base, a little shorter than the sepals, apex subacute. Lip 3-lobed above the middle, 0.65 by 0.45 cm, cuneate at the base, with a slightly thickened median band extending to the base of the midlobe, in front, on the midlobe, with a few transverse rows of crescent-shaped warts; lateral lobes obliquely oblong, obtuse; midlobe more than twice as long as the lateral lobes, broadly obovate, apiculate. Column short, clinandrium 3-lobulate, the lateral lobules obtusely bidentate, the median a little longer, subulate; column-foot concave, 0.3 cm long. Anther rounded-cucullate, glabrous, in front subtruncate.
(after Schlechter, 1912).

Colours:

Flower light yellow or whitish, the lip with faintly red margins.

Habitat:

Epiphyte in hill and montane forest. Altitude 500 to 1750 m.

Distribution:

New Guinea, Solomon Islands.

Distribution New Guinea:

Papua (Manokwari, Nabire, and Jaya Wijaya Regencies); Papua New Guinea (Enga, Simbu, Eastern Highlands, Madang, Morobe, Gulf, Central, and Oro Provinces).

Map: Dendrobium pleianthum Schltr., distribution map.

Cultivation:

Intermediate growing epiphyte.

Flowering time in the wild:

July-November.

Literature:

Lewis, B. & P.J. Cribb. 1991. Orchids of the Solomon Islands and Bougainville: 198, fig. 47 h-k.

Notes:

Dendrobium pleianthum Schltr. must be one of the most floriferous of all orchids. Even though the individual flowers are not spectacular, neither in size nor in colour, a good flowering specimen of this species is an amazing sight. It is probably the only representative of section Pleianthe in New Guinea, as the other described species, Dendrobium dolichocaulon is most probably synonymous. D. pleianthe is somewhat variable in size; in specimens we have seen the leaves were up to 2.3 cm wide. A closely related (or the same) species has been described from Sulawesi: Dendrobium phragmitoides Schltr.