Dendrobium bigibbum

Dendrobium bigibbum Lindl., Paxton's Fl. Gard. 3 (1852) 25. f. 245.

Type: Loddiges cult. s.n. I-1852 (ex Australia) (holo K-LINDL).

Roots many from base of stems, to 20 cm by 1-2 mm, white, smooth, branching. Rhizome short, creeping. Stem erect, slender, 13-18 cm long, few-leaved, cylindrical to fusiform, narrow above swollen basal node then broadening slightly to 3-4 mm in centre and tapering to apex; very wrinkled, brown with brown to black nodal rings; old sheaths silver-grey, persistent, papery. Leaves moderately spaced on upper sections of stem, narrowly ovate, to 8 cm by 10 mm, light green suffused purple on margins, thin, leathery; apex acute, pointed. Inflorescences terminal or lateral from upper nodes, suberect to horizontal, to 15 cm long, slender, with c. 4 well-spaced flowers on the upper half. Peduncle with 4 sheathing sterile bracts; floral bract small. Pedicel and ovary 20 mm long. Flower widely opening, to 5 cm across, sepals and petals slightly recurved. Dorsal sepal erect, oblong, 2.1 cm long, apex obtuse, apiculate, slightly unequal. Lateral sepals wide-spreading, narrowly elliptic, 2.3 cm long, apex acute, mucronate. Mentum conical, c. 1 cm long, apex compressed and slightly decurved. Petals spreading, broadly lanceolate, c. 3 cm long, obtuse, apiculate. Lip porrect, 3.3 by 3.3 cm, 3-lobed; lateral lobes large, erect and incurved to meet over the column, subquadrate, forward margins serrate; midlobe decurved, almost rectangular, 7 by 10 mm, truncate with a small apicule; disc with low crests leading obliquely away from the callus of 5 keels that terminate before midlobe, turning hairy in their final third. Column 4 mm long, stelidia short and rounded; foot at obtuse angle, slender and slightly incurved beyond lip attachment.
(after O'Byrne, 1994).

Colours: Sepals and petals satiny pinkish-mauve with white margins, mentum green underneath. Lip darker purple with deep purple veins on the disc and midlobe; there are 5 purple keels that are covered in short hairs towards their tips. Column and anther purple.

Habitat: Probably epiphytic in seasonally swampy savannah. Altitude 0 to 500 m. O'Byrne (1994) reports a 'sickly' specimen collected in montane forest in the Central Province of Papua New Guinea at 1400 m.

Flowering time in the wild: May to August.

Distribution: New Guinea, Australia.

Distribution in New Guinea: Papua (probably Merauke Regency); Papua New Guinea (probably Western and Gulf provinces, Central Province).

Notes: This is a very well known species in horticulture, but its distribution in New Guinea is largely unsubstantiated. Natural hybrids with species belonging to sect. Spatulata appear to be fairly common.

Cultivation: Warm growing epiphyte, requires dry resting period.