Dendrobium hellwigianum

Dendrobium hellwigianum Kraenzl., Bot. Jahrb. Syst. 16 (1892) 16; in Engl., Pflanzenr. IV. 50. II. B. 21 (1910) 279.

Type: Hellwig 323 (holo HBG).

Erect to spreading, tufted sometimes branching epiphyte to 24 cm high, mature plants often curved, ascending habit of growth due to older pseudobulbs becoming more pendent with age. Roots 0.5-1.5 mm diameter, white. Rhizome usually short but sometimes elongated (with new stems arising 1 or 2 nodes up from base of previously formed pseudobulbs). Pseudobulbs 1-8 by 0.2-0.6(-0.8) cm, fusiform to cylindrical, somewhat constricted at the nodes, sometimes slightly curved, with 1-5 leaves arising from the apex of new stems. Leaves 1.5-16 by 0.05-0.25 cm, erect to suberect, terete to subterete, channelled, apex acute to obtuse, fleshy; sheaths smooth, old sheaths persistent, papery. Inflorescences terminal, arising from both leafy and leafless stems, subsessile, 1-3-flowered; bracts regular, ovate acuminate. Flowers 1.7-3.2 cm long, usually widely opening, lasting c.4-6 months. Median sepal 7-13 by 2-4 mm, narrowly ovate, acute. Lateral sepals 17-31 by 3-6.5 mm, narrowly triangular, acute to acuminate; basal fused part cylindrical to subconical, 3-12 mm long; mentum total length 10-22 mm, tip bilobed or obtuse. Petals 6-11 by 1.5-3 mm, linear to obovate, acute. Lip 14-28 by 2-3.5 mm, subtrilobate, linear-oblanceolate, adnate to column foot at base, apical part free with margins slightly incurved, without a cross-ridge, apex not recurved, acute to subacuminate. Column c. 2.5 mm long; foot 10-22 mm long; anther 1.5-2 mm broad; pollinia c. 1 mm long. Ovary 5-winged with 3 dorsal wings close together and occasionally undulate; pedicel and ovary 15-28 mm long. Fruit 14 by 8 mm, ovoid.
(after Reeve & Woods, 1989).

Colours: Leaves pale green sometimes flushed red, old sheaths greyish white. Sepals and petals pink to purple, greyish white to blue (with purplish mentum) or creamy-yellow, lip apex bright orange to orange-red; ovary purplish pink.

Habitat: Epiphyte in montane forest, rarely terrestrial. Altitude 1400 to 2700 m.

Flowering time in the wild: February, May, July-December.

Distribution: New Guinea.

Distribution in New Guinea: Papua (Swart (=Ilim) Valley); Papua New Guinea (widespread in the mountains).

Map: HELLWMAP.JPG [Dendrobium hellwigianum Kraenzl., distribution map, redrawn from T.M. Reeve & P.J.B. Woods, Notes Roy. Bot. Gard. Edinburgh 46 (1989) 289, map 15, with new record added.]

Notes: Dendrobium hellwigianum is one of the most common and most widespread 'Oxyglossum' species in the eastern half of New Guinea. Reeve & Woods (1990) could not report any specimens from West New Guinea, but in fact it has been found there as well (Bergman 211 & 746, S), as was only to be expected.

This species was named in honour of its discoverer, Franz Hellwig (1861-1889), a botanist with the German New Guinea Company. He was one of the first botanists to venture into the montane regions, but died shortly afterwards at Finschhafen, having been in the colony for only 14 months. His specimens were forwarded to Berlin where many novelties, including several orchid species, were described by Friedrich Kraenzlin. Type material has come to light in Hamburg, making the selection of a neotype by Reeve & Woods (1990) unnecessary.

When not in flower, Dendrobium hellwigianum is readily recognised by the fleshy terete or subterete leaves which superficially resemble Allium schoenoprasum, the garden chives.

The flowers are similar to those of Dendrobium violaceum in colour and general shape, but differ in the smaller size, the proportionately narrower tepals, and in the shape of the ovary cross-section. The three upper wings on the ovary of Dendrobium hellwigianum are close together and can give the superficial appearance of the ovary being 3-winged when in fact it is 5-winged. This error was made by Kraenzlin in his original description, but subsequently (1910) he had a closer look and corrected it after Schlechter had drawn attention to the importance of ovary wings and ribs in classification of the Oxyglossum species.

A natural hybrid between Dendrobium hellwigianum and Dendrobium violaceum is recorded.

Cultivation: Cool growing epiphyte, requires a light, well drained position, but strongly resents both soggy conditions as well as desiccation.

(largely after Reeve & Woods, 1989)