Orchids of New Guinea

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Dendrobium atroviolaceum

Dendrobium atroviolaceum Rolfe, Gard. Chron. (1890, I) 512; (1892, I) 214; Hook. f. Bot. Mag. (1894) t.73.

Type: Veitch cult. (XII-1894, New Guinea) (holo K).

Synonyms:

Latourea atroviolacea (Rolfe) Brieger, in Schltr., Orchideen, ed. 3, I/A (1981) 727.
Latourorchis atroviolacea (Rolfe) Brieger, in Schltr., Orchideen, ed. 3, I/A (1981) 727.
Sayeria atroviolacea (Rolfe) Rauschert, Feddes Repert. 94 (1983) 466.
Dendrobium macgregorii F.Muell. & Kraenzl., Österr. Bot. Zeitschr. 44 (1894) 301.
- Type: MacGregor s.n.(1889, South-east I., Louisiades).

An epiphytic herb. Pseudobulbs clustered, erect, subclavate, 3-6-noded below leaves, 11-31 by 0.4-0.8 cm, yellow, 2-leaved at apex. Leaves spreading, coriaceous, elliptic-ovate to narrowly elliptic, minutely emarginate at rounded or obtuse apex, 5-12 by 2-3.8 cm. Inflorescence erect or arcuate, few-flowered, 7-15 cm long; bracts ovate, acute or apiculate, 5-9 by 4-6 mm. Flowers subnutant, large; pedicel and ovary 2-3.5 cm long. Dorsal sepal ovate, acute, 2-2.8 by 0.9-1.3 cm; lateral sepals falcate, obliquely ovate-lanceolate, acuminate, 1.5-2.5 by l-1.3 cm; mentum obliquely conical, 0.8-1 cm long. Petals obovate, obtuse to subacute, 2.5-3 by 1.3-1.8 cm. Lip strongly recurved, 3-lobed, 1.3-2 by 1.8-2.6 cm; side-lobes erect, semi-elliptic, rounded at apex; midlobe much longer than side-lobes, broadly ovate, acute; callus 3-ridged, running onto base of midlobe. Column 4 mm long; foot 0.8-1 cm long.
(after Cribb, 1983).

Colours:

Sepals and petals cream-coloured, marked with violet spots; lip yellow, heavily veined with violet.

Habitat:

Epiphyte on large trees e.g. Castanopsis in rainforests. Altitude 300-750 m.

Distribution:

New Guinea (islands off the eastern coast); Louisiade Archipelago.

Distribution New Guinea:

Papua (Jayapura Regency); Papua New Guinea (D'Entrecasteaux Islands and Louisiades only).

Map: Dendrobium atroviolaceum Rolfe, distribution map, redrawn from P. Cribb, Kew Bull. 38 (1983) 234, map 2, with new record added.

Cultivation:

Warm growing epiphyte.

Flowering time in the wild:

July to December.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Genus Dendrobium
Section Latouria
Species Dendrobium atroviolaceum

Literature:

Cribb, P.J. 1983. Kew Bull. 38: 259, fig. 6, pl. 10C, 15E, F, map 2.
Rolfe, R.A. 1894. Curtis's Bot. Mag. t. 7371.
van Bodegom, J. 1973. Enige orchideeën van West Nieuw Guinea: 74.

Notes:

Dendrobium atroviolaceum Rolfe is by its nodding flowers, distinctive flower colour and short strongly recurved lip easy to distinguish from similar species such as Dendrobium convolutum Rolfe and Dendrobium engae T.M.Reeve.

Dendrobium atroviolaceum Rolfe has beern in favour with hybridists despite the nodding habit of its flowers. Dendrobium Nellie Slade, a hybrid of this species with Dendrobium rhodostictum F.Muell. & Kraenzl., has an extended flowering period, grows vigorously and has attractively coloured flowers. Van Bodegom (1973) gives a surprising record from the Cyclop Mountains near Jayapura.
(largely after Cribb, 1983).