Orchids of New Guinea

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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).

Synonyms:

Callista subacaulis (Reinw. ex Lindl.) Kuntze, Rev. Gen. Pl. (1891) 655.
Pedilonum subacaule (Reinw. ex Lindl.) Rauschert, Feddes Repert. 94 (1983) 464.
Dendrobium delicatulum Kraenzl., Bot. Jahrb. Syst. 16 (1892) 17.
- Type: Hellwig 303 (holo HBG).
Pedilonum delicatulum (Kraenzl.) Rauschert, Feddes Repert. 94 (1983) 459.
Dendrobium begoniicarpum J.J.Sm., Bull. Jard. Bot. Buitenzorg, sér. 2, 3 (1912) 74; Nova Guinea 12, 1 (1913) 67, t. 18, fig. 53.
- Type: Gjellerup 566 (holo BO).
Pedilonum begoniicarpum (J.J.Sm.) Rauschert, Feddes Repert. 94 (1983) 457.
Dendrobium oreocharis Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 533; 21 (1923) t. 180, fig. 675.
- Type: Schlechter 18753 (holo B, lost; iso AMES, BO, E, L).
Pedilonum oreocharis (Schltr.) Rauschert, Feddes Repert. 94 (1983) 462.
Dendrobium tricostatum Schltr., Repert. Spec. Nov. Regni Veg. Beih. 1 (1912) 532; 21 (1923) t. 180, fig. 674.
- Type: Schlechter 20207 (holo B, lost).
Pedilonum tricostatum (Schltr.) Brieger, in Schltr., Orchideen, ed. 3, I/A (1981) 684.
Dendrobium begoniicarpum J.J.Sm. var. parviflorum J.J.Sm., Nova Guinea 12, 1 (1913) 68.
- Type: Gjellerup 532 (holo BO).
Dendrobium junzaingense J.J.Sm., Bot. Jahrb. Syst. 66 (1934) 197.
- Type: Mayr 704 (holo BO).
Pedilonum junzaingense (J.J.Sm.) Rauschert, Feddes Repert. 94 (1983) 460.

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).

(largely 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 shrubs and on tree trunks, occasionally terrestrial or lithophytic. Altitude 750 to 2500 m.

Distribution:

Moluccas, New Guinea, Solomon Islands.

Distribution 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: 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.

Cultivation:

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

Flowering time in the wild:

Throughout the year.

Classification:

Family Orchidaceae
Subfamily Epidendroideae
Tribe Dendrobieae
Subtribe Dendrobiinae
Section Calyptrochilus
Species Dendrobium subacaule

Literature:

Schlechter, R. 1912. Repert. Spec. Nov. Regni Veg. Beih. 1: 532.
Schlechter, R. 1923. Repert. Spec. Nov. Regni Veg. Beih. 21: t. 180, fig. 673.
Reeve, T.M. & P.J.B. Woods. 1981. Orchadian 7: 18, fig.
Reeve, T.M. & P.J.B. Woods. 1990. Notes Roy. Bot. Gard. Edinburgh 46: 212, fig. 14, pl. 10A, B.
Lewis, B. & P.J. Cribb. 1991. Orchids of the Solomon Islands and Bougainville: 189.
Schuiteman, A. & J.F. Wanma. New and noteworthy Orchid Species from the Arfak Mountains, West Papua Province, Indonesia. Malesian Orchid Journal 20 (2017) 87, fig. 25

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.