Dendrobium johnsoniae F.Muell., S. Sci. Rec. 2 (1882) 95.
Type: Chalmers s.n. (New Guinea, E. Peninsula) (holo MEL; iso K).
An erect epiphytic herb. Pseudobulbs stout, subclavate, 4-6-noded below leaves, 20-30 by 0.8-1.1 cm, yellow, 4-5-leaved at apex. Leaves coriaceous, elliptic or oblong-elliptic, obtuse, 8-11 by 3.5-4.5 cm. Inflorescence terminal or from below leaf bases, erect or suberect, 17-27 cm long, few-many-flowered; bracts elliptic-lanceolate, acute, 4-7 mm long. Flowers large, attractive, white with purple lines on side lobes of lip and base of column; pedicel and ovary 1.7-2.2 cm long. Dorsal sepal lanceolate, acuminate, 2.6-2.8 by 0.7-0.8 cm; lateral sepals obliquely lanceolate, acuminate, 2.6-3.4 by 1-1.1 cm; mentum obliquely conical, 8-9 mm long, somewhat nose-like towards apex. Petals narrowly clawed, rhombic above, acuminate, 4.2-5 by 1.8-3 cm. Lip not recurved, 3-lobed, 3.5-4.6 by 2-3 cm; side-lobes erect, subquadrate, with erose margins; midlobe much longer than side-lobes, ovate-lanceolate, acuminate, narrow at base; callus fleshy, obscurely 2-ridged at base. Column short, 3 mm long, with two hook-like stelidia at apex; foot 7-9 mm long.
(after Cribb, 1983).
Colours: Flowers white with purple to reddish lines on side lobes of lip and base of column.
Habitat: Epiphyte in montane forests of Araucaria, Albizia, Casuarina etc. Altitude 500 to 1200 m.
Flowering time in the wild: April to November.
Distribution: New Guinea, Solomon islands.
Distribution in New Guinea: Papua (Manokwari, Yapen Waropen, and Jayapura Regencies); Papua New Guinea (Sandaun, Madang, Morobe, Central, and Oro Provinces).
Map: JOHNSMAP.JPG [Dendrobium johnsoniae F.Muell., distribution map, redrawn from P. Cribb, Kew Bull. 38 (1983) 234, map 2, with new records added.]
Notes: According to Cribb, Dendrobium johnsoniae is allied to Dendrobium rhodostictum and Dendrobium otaguroanum but is readily distinguished by its pure white flowers veined with purple-red on the lip side-lobes only, its rhombic petals and an elongate lip with a lanceolate midlobe.
The distribution of this species in New Guinea and the Solomon Islands closely parallels that of Dendrobium spectabile.
(after Cribb, 1983).
Cultivation: Intermediate growing epiphyte.