Orchids of New Guinea

Dendrobium contextum

Dendrobium contextum Schuit. & de Vogel ex J.M.H.Shaw, Orchid Rev. Suppl. 111 (2003) 61

Type: Canberra Nat. Bot. Garden cult., 29 Jul. 1996 (Clements 8592) (holo CANB)

Synonyms:

Dockrillia convoluta M.A.Clem. & D.L.Jones, Lasianthera 1 (1996) 11, fig. 3, pl. 5C.
- Type: Canberra Nat. Bot. Garden cult., 29 Jul. 1996 (Clements 8592) (holo CANB).
Dendrobium contextum Schuit. & de Vogel, Blumea 48 (2003) 509 (isonym)

Pendulous epiphyte forming sparse clumps to about 1 m long. Aerial roots absent. Stems straight, 3-8 cm by 1-2 mm. Leaves linear-terete, 10-30 cm by 3-4 mm, pendulous. Racemes 5-7 cm long, wiry, arising singly from nodes at the leaf base, bearing 3-7 flowers. Pedicels 8-12 mm long, filiform. Ovary 1-2 mm long, hardly developed at anthesis. Flowers 2.5-3 cm across, opening widely, fragrant. Dorsal sepal very narrowly ovate-lanceolate, 1-1.4 cm by 2.5-3 mm, obliquely erect; apex long-acuminate. Lateral sepals asymmetrically lanceolate, very strongly falcate, 1-1.4 cm by 3.5-4 mm, divergent; apex acuminate. Petals narrowly elliptical-lanceolate, 1-1.4 cm by c. 1.3 mm, spreading; apex attenuate. Lip thick textured, porrect in the basal half, apical half strongly recurved, 0.9-1.3 cm by 4-6 mm when flattened; lateral lobes elliptic-oblong, 6-7 mm by 2 mm, incurved, outer margins papillate; midlobe ovate-elliptic, 5.5-6 mm by 4.5-5 mm, margins strongly incised and convolute, papillate, apex long-acuminate; callus of three yellow ridges, inner ridge narrow and straight in the distal half, outer ridges very broad (c. 0.5 mm wide), curving outwards near the base, then inwards towards the midlobe, becoming intensely convolute on the midlobe, ending nearly at the apex, 3 or 4 pairs of irregular ridges radiating to the marginal folds. Column 2.5-3 mm by 2 mm, porrect from the end of the ovary, glabrous, the wings lacerate, extending about half way up the anther; column foot 4-4.5 mm by 2 mm, at about 10 degrees to the column, curved, broadly channelled, glabrous. Stigma c. 2 mm by 1.5 mm, sunken. Anther 1.5 mm by 1.5 mm, with a lacerate rostrum. Pollinia oblong c. 1.2 mm long, waxy. Capsule not seen.
(after Clements & Jones, 1996).

Colours:

Leaves dark green. Flower yellowish, heavily spotted, striped and suffused with dark red; lip dark red, margins darker, apex yellow. Column yellowish with reddish markings. Anther brownish with purplish markings. Pollinia orange.

Habitat:

Epiphytic on Casuarina trees in open montane swampland. Altitude not recorded, undoubtedly above 1200 m judging from the type locality

Distribution:

New Guinea (endemic).

Distribution New Guinea:

Papua New Guinea (Central Province).

Map: Dendrobium contextum Schuit. & de Vogel, distribution map.

Cultivation:

Cool growing epiphyte.

Flowering time in the wild:

Not known. Flowers of cultivated plants last 3 to 5 days.

Classification:

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

Notes:

Dendrobium contextum Schuit. & de Vogel ex J.M.H.Shaw is characterised by the following combination of features: flowers yellowish, heavily spotted and suffused with dark red; lip relatively large (to 13 mm by 6 mm), dark red with darker margins, papillate, with a yellowish long-acuminate apex, with prominent lateral lobes and, an ovate-elliptic mid-lobe with incised and convoluted margins; and an extremely convoluted mass of callus ridges on the lip mid-lobe.
(after Clements & Jones, 1996).