Dendrobium helix

Dendrobium helix P.J.Cribb, Orchadian 6 (1980) 174, fig.

Type: Slade s.n. (New Britain) (holo K).

An epiphytic herb. Stems clustered, 1-2.2 m or more tall, cane-like, slightly swollen at base, up to 7.5 cm diam. Leaves coriaceous, elliptic or ovate-elliptic, obtuse or rounded at obscurely bilobed apex, up to 16 by 6.5 cm, articulated to a tubular scarious basal sheath up to 3 cm long. Inflorescences 1-several, spreading to erect, up to 14 cm long, laxly up to 20-flowered; bracts ovate, acute or acuminate, 4-5 mm long. Flowers erect or nodding; pedicel and ovary c. 4.5 cm long. Dorsal sepal recurved and undulate, oblong-lanceolate, obtuse, 2.7-3 by 0.8 cm; lateral sepals recurved and undulate, obliquely oblong, obtuse, 2.6-2.7 by 1-1.2 cm; mentum shortly obliquely conical 9-10 mm long. Petals spathulate, rounded or obtuse, 3-4.5 by 0.5-1 cm, (1-)2-4 times twisted. Lip 3-lobed, 2-2.2 by 1.1-1.2 cm; side-lobes narrowly elliptic, truncate and spreading in front; midlobe recurved, oblong, apiculate; callus of 3 low ridges tapering out on centre of midlobe. Column 4 mm long, with two apical ventral acuminate stelidia.
(after Cribb, 1986).

Colours: Stems yellow-orange when dry. Leaf sheath often striped with purple. Flowers yellow, pinkish or brown with a maroon or pink central zone and violet veins on lip.

Habitat: Epiphyte on trees by coast, in coastal forest, and in rainforest. Altitude 0-150 m.

Flowering time in the wild: throughout the year.

Distribution: Bismarck Archipelago (New Britain).

Distribution in New Guinea: Papua New Guinea (New Britain).

Map: HELIXMAP.JPG [Dendrobium helix P.J.Cribb, distribution map, redrawn from P. Cribb, Kew Bull. 41 (1986) 658, map 6, with new record added.]

Notes: Dendrobium helix is one of the larger-flowered and most attractive species in sect. Spatulata. It is a variable orchid particularly in its flower colour, attitude and the degree of twisting of the petals. However, it is readily characterised by its lip which has a small recurved apiculate midlobe, side lobes that spread widely at the apex and a violet or lilac callus of three ridges which taper to their apices on the apical half of the midlobe. Its column is also quite distinctive with two elongate acuminate stelidia at the apex.

Several forms of Dendrobium helix that have been introduced into cultivation in recent years have been given fancy names, such as 'Pomio Brown', 'Talasea Lime Yellow' and 'Talasea Mushroom Pink'.

In most specimens, the petals are twisted three or four times but P.J.Cribb (1986) also mentions plants of 'Pomio Brown' in which the petals are only half twisted and much shorter than usual.
(after Cribb, 1986).

Cultivation: Warm growing epiphyte, prefers light shade and plenty of water throughout the year.