Orchids of New Guinea

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Dendrobium rigidum

Dendrobium rigidum R.Br., Prodr. (1810) 333.

Type: Illust. Banks s.n. (Tropical Australia).

Synonyms:

Callista rigida (R.Br.) Kuntze, Rev. Gen. Pl. (1891) 655.
Dockrillia rigida (R.Br.) Rauschert, Feddes Repert. 94 (1983) 447.
Dendrobium desmotrichoides J.J.Sm., Bull. Dép. Agric. Indes Néerl. 19 (1908) 16; Nova Guinea 8, 1 (1909) 63, t. 23, fig. 72.
- Type: Bogor cult. (Jaheri 60) s.n. (Merauke River) (holo BO).
Dockrillia desmotrichoides (J.J.Sm.) Brieger, in Schltr., Orchideen, ed. 3, I/A (1981) 745.

Rhizome to c. 12.5 cm long, creeping, branching. Stems 1.8 cm long, consisting of c. 3 internodes, of which the upper one is largest, concave at the apex, and obconical-thickened apically, the terminal internode 1.25 cm by 3.5 mm, 1-leaved. Leaves inserted in the apical cavity of the stem, laterally compressed, obliquely lanceolate, 4.5 by 1 cm, apex obtuse, very fleshy, rigid, verruculose. Inflorescences arising near the apex of the stem behind the leaf, very short; peduncle 0.9 cm long, slender, peduncle-scales few, membranous, c. 2-flowered (up to 6 flowered, fide O'Byrne, 1994). Pedicel and ovary 0.6 cm long. Flowers 1.45 cm across, fragrant. Dorsal sepal ovate-oblong, 0.75 cm by 3.7 mm, incurved at the base, convex, apex obtuse. Lateral sepals triangular, 0.75 cm by 6 mm, apex subacute; concave, 5-nerved; mentum obtuse-retuse. Petals narrowly lanceolate, slightly widened in upper part, 0.8 cm by 2 mm, slightly convex, 3-nerved, apex acute. Lip 3-lobed near the middle, 0.9 by 0.55 cm, concave, with 3 keels, the lateral ones straight, extending to the base of the midlobe, the median keel longer and in the basal part lower than the laterals, straight until the base of the midlobe, on the midlobe strongly wavy; lateral lobes erect, porrect, obliquely ovate-triangular, hardly extending beyond the apex of the column; midlobe larger, obovate, carnose, obtusely apiculate. Column 0.25 cm long, clinandrium 3-lobulate, the lateral lobules triangular, acute, the median tooth-like, shorter, stigma large, deeply concave; column-foot at almost right angles to the ovary, 0.35 cm long, curved, obtuse. Anther cucullate, flattened in front, apex puberulous.
(after Smith, 1909 - as Dendrobium desmotrichoides).

Colours:

Sepals and petals pale yellowish green, outside with sparse reddish dots, lip pale yellow, on the lateral lobes with longitudinal red stripes, on the midlobe inside with red spots and stripes, outside with red dots. Column pale green with red margins and markings; anther pale green, pollinia bright yellow.

Habitat:

Lowland epiphyte, usually growing in exposed positions, also lithophytic. Altitude 0 to 860 m.

Distribution:

New Guinea, Aru Islands, Australia.

Distribution New Guinea:

Papua (Merauke Regency); Papua New Guinea (Gulf, Morobe, Central, Oro, and Milne Bay Provinces).

Map: Dendrobium rigidum R.Br., map of distribution, redrawn from N.H.S. Howcroft, from Orchadian 5 (1978) 183.

Cultivation:

Warm growing epiphyte, requires full sun.

Flowering time in the wild:

Throughout the year. Flowers last 3-4 days (fide O'Byrne).

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Genus Dendrobium
Section Rhizobium
Dendrobium rigidum

Literature:

Howcroft, N.H.S. 1978. Orchadian 5: 182, fig.
O'Byrne, P. 1994. Lowland Orchids of Papua New Guinea: 316, fig., pl.

Notes:

Dendrobium rigidum R.Br. is easily recognised by the 1-leaved shoots carrying a single laterally flattened leaf.