Dendrobium subclausum

Dendrobium subclausum Rolfe, Bull. Misc. Inform. Kew (1894) 361.

Type: Veitch cult. s.n. (VII-1893, Moluccas) (holo K).

Stems crowded, erect, slender, terete, flexuose in upper part, branching, 30-45 cm long. Leaf sheaths verrucose-rough. Leaves linear-oblong, 2-4 by 0.25-0.4 cm, apex subobtuse. Inflorescences short, racemose, few-flowered. Floral bracts oblong-lanceolate, keeled near apex, strongly concave, 0.4-0.7 cm long, apex acute. Pedicel and ovary 2.2 cm long. Flowers c. 2 cm long. Dorsal sepal ovate-lanceolate, 0.8 cm long, apex subobtuse. Lateral sepals ovate-triangular, indistinctly keeled outside, mentum elongated-conical, 1.5 cm long. Petals ovate-lanceolate, 0.9 cm long, apex subobtuse. Lip clawed, narrow, a little widened above the middle, strongly concave, 1.8 cm long, apex abruptly inflexed, with 3 folds, cucullate, margin fimbriate. Column very short.
(after Kraenzlin, 1910).

Colours: Flower bright orange to light red, dorsal sepal, petals and upper half of lateral sepals usually bright yellow. Flower buds green. The type collection, from an unspecified locality in the Moluccas, was said to have orange-vermilion flowers, apparently without contrasting apices.

Habitat: Epiphyte in montane forest, sometimes in deep shade in moss forest, also terrestrial in montane grassland. Altitude 1000 to 3250 m.

Flowering time in the wild: Throughout the year. Flowers long-lasting.

Distribution: Moluccas, New Guinea.

Distribution in New Guinea: Papua and Papua New Guinea, widespread and common in almost all mountain ranges.

Notes: The exact delimitation of Dendrobium subclausum is perhaps the greatest unsolved taxonomic problem at species level in Dendrobium, at least as far as the New Guinea members of this genus are concerned. On almost every mountain in New Guinea above circa 2000 m altitude one can come across a strikingly bicoloured (orange-and-yellow or red-and-yellow) Dendrobium with branching stems and narrow leaves. It seems likely that this is nearly always to be identified as Dendrobium subclausum, in spite of the fact that an extensive variation can be noted in such characters as the thickness and height of the stems, the shape and width of the leaves, the 'wartyness' of the leaf-sheaths, the number of flowers in the inflorescence, details of the flowers, etc. Many names, based on such differences, have been proposed for species in this alliance, most of which are not as yet included in the synonymy of D. subclausum on this CD-ROM. It is probable, for example, that Dendrobium angiense, Dendrobium calyptratum, Dendrobium dichroma, Dendrobium flammula, Dendrobium fruticicola, Dendrobium infractum, Dendrobium paspalifolium, and Dendrobium riparium are better treated as synonyms of D. subclausum, as already proposed by J.J. Wood (1986), but we consider it preferable to postpone such decisions until the many hundreds of specimens stored in herbaria have been thoroughly examined. We have decided to reproduce here a description by Kraenzlin/Rolfe based on the type material of Dendrobium subclausum, even though this descriptions leaves much to be desired in detail. At least it refers to the true Dendrobium subclausum.

Three varieties, next to the typical variety subclausum, have been proposed by J.J. Wood: var. phlox, var. speciosum and var. pandanicola, see below.

Cultivation: Treat as cool growing epiphyte, requiring light shade and frequent waterings throughout the year.


Key to the varieties:

1a. Flower not entirely yellow, but orange and yellow, orange-red, etc. ... 2
1b. Flower entirely yellow .... Dendrobium subclausum Rolfe var. pandanicola J.J.Wood.

2a. Flower less than 3 cm long, sepals and petals moderately spreading (flower bell-shaped) ... 3
2b. Flower 3-4 cm long, sepals and petals widely spreading to reflexed (flower not bell-shaped) ... Dendrobium subclausum Rolfe var. speciosum J.J.Wood.

3a. Leaf sheaths smooth to papillose or verrucose, not hairy ... Dendrobium subclausum Rolfe var. subclausum
3b. Leaf sheaths papillose-hairy ... Dendrobium subclausum Rolfe var. phlox (Schltr.) J.J.Wood.


Dendrobium subclausum Rolfe var. phlox (Schltr.) J.J.Wood, Kew Bull. 41 (1986) 819.

Basionym: Dendrobium phlox Schltr.

Rhizome very short, roots elongated, filiform, flexuose, glabrous. Stems crowded, patent, elongated, robust, up to 70 cm long, many-leaved, unbranched or sparsely branched. Leaf sheaths entirely covering the stem, minutely rugulose-verruculose (papillose-hairy, fide J.J. Wood). Leaves subpatent, lanceolate-elliptic to lanceolate-ligulate, 2.5--8.5 by 0.8--1.9 cm, apex obliquely apiculate to acute. Inflorescences racemose, short, rather densely several-flowered. Floral bracts ovate to lanceolate, much shorter than the pedicel and ovary, apex acuminate, glabrous. Pedicel and ovary 2.6--2.8 cm long, slender, glabrous. Flowers resupinated or not, c. 3 cm long. Dorsal sepal elliptic, 1.1 cm long, apex obtuse or minutely apiculate. Lateral sepals obliquely elliptic, much widened at the base, 1.1 cm long, apex obtuse or minutely apiculate; mentum obliquely conical, c. 2 cm long, obtuse. Petals obliquely elliptic, 1 cm long, apex obtuse. Lip strongly concave, from a narrow base becoming obovate in upper half, 2.4 by 0.8 cm, apical margin pectinate-lacerate. Column short, clinandrium 3-lobulate, the lateral lobules rounded, the median tooth-like; column-foot linear, 2 cm long, concave, in lower half adnate to the margins of the lip.
(after Schlechter, 1912).

Colours: Flowers golden yellow, the mentum, lip and ovary orange-red.

Habitat: Epiphyte in lower montane forest. Altitude 1200--1300 m.

Flowering time in the wild: September.

Distribution: New Guinea (endemic).

Distribution in New Guinea: Papua New Guinea (Madang Province: Finisterre Mountains).

Cultivation: Cool growing epiphyte.


Dendrobium subclausum Rolfe var. pandanicola J.J.Wood, Kew Bull. 41 (1986) 817.

Type: Reeve 302 (holo K; iso BISH, CBG, E, LAE, L).

Stems numerous, 23-35 cm by 3-4 mm, much branched, flexuose, often fractiflex, semi-erect to pendulous, covered in scarious, evanescent sheaths. Leaves lanceolate or lanceolate-ligulate, 3.5-7.5 by 0.4-1 cm, apex acute, apiculate, or obtuse and mucronate, often slightly erose, texture thin and coriaceous, sheaths smooth, never rugulose, verruculose or hirsute. Inflorescences 3-8-flowered, several borne 1.5-2.2 cm apart on the nodes of the previous year's leafless stems; floral bracts 3-7 mm long, several clustered at each node, ovate-elliptic, acute or acuminate, smooth, scarious. Flowers pendent, glabrous. Pedicel with ovary 1.5-2.2 cm long. Dorsal sepal ovate, 0.5-0.7 cm by 3.5-5 mm, obtuse. Lateral sepals obliquely ovate, 0.5-0.8 cm by 4-7 mm, obtuse, connate towards base and forming an obtuse mentum c. 1-2 cm long. Petals 0.5-0.7 cm by 2.5-3.5 mm, obliquely elliptic, obtuse. Lip obovate-ligulate, concave, 1-5 cm long, 4 mm broad at apex, lower portion adnate to column foot, apex strongly cucullate, pectinate. Column 0.3 by 0.3 cm, quadrate, foot 1-1.2 cm long, ligulate, slightly concave; anther 2 by 2 mm, quadrate, dorsally retuse, minutely papillose.
(after Wood, 1986).

Colours: Flower bright yellow or lemon-yellow, buds flushed green. Stems distinctly yellowish.

Habitat: Usually epiphytic on Pandanus, also terrestrial in montane grassland. Altitude 1500-2700 m.

Flowering time in the wild: June, August, November, December.

Distribution: New Guinea (endemic).

Distribution in New Guinea: Papua New Guinea (Enga and Southern Highlands Provinces).

Notes: Mainly distinguished by its uniform yellow flowers.

Cultivation: Cool growing epiphyte, prefers light position.


Dendrobium subclausum Rolfe var. speciosum J.J.Wood, Kew Bull. 41 (1986) 818.

Type: Reeve 548 (holo K; iso AMES, BISH, BO, CBG, E, LAE, L, NSW, UPNG).

Stems slender, branching. Leaf-sheaths papillose-verruculose, persistent. Leaves lanceolate to linear-lanceolate, 5.5-10 by 1 cm, acute. Inflorescences 3-5-flowered; floral bracts smooth. Flowers 3-4 cm long; mentum 1.7-2.8 cm long. Sepals and petals usually reflexed.

Colours: Flower largely orange to orange-red, except for upper portion of sepals and petals, which are golden yellow; column yellow.

Habitat: Epiphytic or terrestrial. Altitude 1800 m.

Flowering time in the wild: July.

Distribution: New Guinea (endemic).

Distribution in New Guinea: Papua New Guinea (Southern Highlands Province).

Notes: Distinguished by its large flowers with widely spreading sepals and petals. The flowers are much alike in shape and size to those of Dendrobium chrysopterum, but in habit these taxa are quite dissimilar.

Cultivation: Intermediate growing epiphyte.