Dendrobium subacaule

Dendrobium subacaule Reinw. ex Lindl., J. Proc. Linn. Soc., Bot. 3 (1859) 11.

Type: Reinwardt s.n. (Moluccas, Tidore, Mt. Tidore) (holo K, iso L, W).

Small erect to suberect tufted (occasionally creeping and mat-forming) epiphyte, 1-5 cm high. Roots 0.4-1 mm diameter. Rhizome usually very short, occasionally elongated, up to 0.6 cm long. Pseudobulbs 0.3-1.5 by 0.1-0.45 cm, clavate, globose, obclavate, fusiform or cylindrical, apex 2-3(-4)-leaved. Leaves 0.4-2.1 by 0.1-0.5(-0.75) cm, suberect to spreading, lanceolate to elliptic, apex acute to obtuse, mucronate, green to purplish red; sheaths slightly ribbed. Inflorescences terminal, arising mainly from leafy stems, 1-3-flowered, subsessile; bracts ovate, apiculate to acuminate. Flowers 0.9-1.9 cm long, widely opening, lasting c.6 months. Median sepal 3.5-7.5 by 1.5-3 mm, oblong-ovate to oblong-triangular, acute to subacuminate or apiculate, carinate (mid-vein). Lateral sepals 9-18.5 by 2-4 mm, oblique ovate-triangular, apiculate to acuminate, usually keeled; basal fused part 2-6 mm long, cylindrical to subconical; mentum total length 6-l 1 mm tip obtuse or shortly bilobed. Petals 3-7 by 0.7-1.7 mm, oblique, linear to lanceolate, acute to acuminate. Lip 7.5-17 by 1.5-2.3 mm, subtrilobate, linear-oblanceolate, adnate to column foot at base, upper margins incurved, without a cross-ridge, apex cuspidate, unbent or slightly deflexed. Column 1.8-2.5 mm long; foot 6-l 1 mm long; anther 1-1.8 mm broad; pollinia 0.5-l mm long. Ovary sharply 3-winged with dorsal wing often projecting up behind base of dorsal sepal; pedicel and ovary 7-18 mm long. Fruit (immature) 6 by 3 mm narrowly oblong.
(after Reeve & Woods, 1989).

Colours: Flowers red, purplish red, orange-red, orange or yellowish, with orange lip.

Habitat: Epiphyte, usually on small twigs and branches, but also on tree trunks, occasionally terrestrial or lithophytic. Altitude 750 to 2500 m.

Flowering time in the wild: Throughout the year.

Distribution: Moluccas, New Guinea, Solomon Islands.

Distribution in New Guinea: Papua (Vogelkop Peninsula, Mt. Carstenz, Idenburg River, Cyclop Mountains, Orion Mountains); Papua New Guinea (Sandaun, Enga, Southern Highlands, Western Highlands, Eastern Highlands, Madang, Morobe, Central and Milne Bay Provinces).

Map: SUBACMAP.JPG [Dendrobium subacaule Reinw. ex Lindl., distribution map, redrawn from T.M. Reeve & P.J.B. Woods, Notes Roy. Bot. Gard. Edinburgh 46 (1989) 286, map 9.]

Notes: Dendrobium subacaule is one of the smallest species in section Pedilonum and is readily recognised by its short lanceolate to elliptic leaves and its red or orange flowers which have a sharply 3-winged ovary. It usually grows in small tufts, sometimes seen in large numbers, but a few collections from SE New Guinea exhibit a more distinct creeping and mat-forming habit (e.g. Cruttwell 843 from the Milne Bay Province). This species has sometimes been confused with Dendrobium parvulum but the latter can always be distinguished by its 5-ribbed ovary. The other close ally, Dendrobium pachythrix, also differs by its 5-ribbed ovary which, with the sepals, has an indumentum of short thick hairs.
(largely after Reeve & Woods, 1989).

Cultivation: Dendrobium subacaule seems difficult to grow and requires very good aeration and drainage in a cool greenhouse.