Distichorchis uniflora

The following article was written for the Orchid Species Bulletin published by the Orchid Species Society, which is based in Brisbane, Queensland in January 1998, and updated in December 2024.
Bear in mind that any cultivation notes refer to the subtropical conditions of Southern Queensland, Australia.

Distichorchis uniflora (Griff.) M.A.Clem. was first described by William Griffith as Dendrobium uniflorum in Notulae ad Plantas Asiaticas in 1851. The specific epithet comes from the Latin uni (one), and florus (flowered), referring to the single-flowered inflorescences.

Morphological and molecular studies show that the generic limits of Dendrobium need to be reviewed. Based upon these studies, Mark Clements and David Jones established the genus Distichorchis M.A.Clem. & D.L.Jones in The Orchadian in 2002. Clements and Jones based the new genus on Dendrobium sect. Distichophyllum Hook.f., with Ds. uniflora as the type species.

Plants of the World Online [POWO] accepts Distichorchis as a synonym for Dendrobium. I prefer a consistent taxonomic classification of Orchidaceae, which does not rely predominantly on DNA and genetic information. Instead, I prefer to acknowledge ecology, pollination biology, breeding behaviour, as well as plant habit and floral characteristics. I recognise Distichorchis as distinct from Dendrobium.

Distichorchis are sympodial plants, which produce cane-like, non-pseudobulbous stems that bear numerous, two-ranked leaves along the upper portion, or sometimes most of their length. Its stems produce very short, or much-reduced inflorescences, with sometimes several simultaneous from consecutive nodes. The very short racemes are single-flowered or rarely twin-flowered. Its flowers have a short column and a longer column-foot that forms a short nectar-producing spur, with the base of the fleshy lip.

Ds. uniflora is a sympodial, epiphytic plant, which produces clustered, erect, cane-like stems. The stems are slender, spindle-shaped, and (15-) 30-40 (-75) cm long. Four-grooved or sometimes slightly 4-angled above the middle, the stems are slightly swollen in the middle, with leaves borne along the whole length. Sometimes the leaf sheaths may be marked with red stripes. Alternating in two ranks, the elliptic-oblong to lance-shaped leaves are 2.5-4 (-7) cm long and 1 cm broad. Twisted at the base, all the leathery, shiny leaves lie in one plane, and have unequally bilobed and acute tips.

The flowers of Ds. uniflora are 2-3 cm across are borne singly from nodes opposite the leaves on the matured stems. Heavily textured and waxy, the flowers have creamy white, reflexed sepals and petals that become dull yellow with age. The distinctly 3-lobed lip is lowermost, and is white to pale greenish yellow or green, and may be marked with yellow to brown stripes towards the base. Running along the centre of the lip are three keels that may be violet, brown, orange or crimson. Ds. uniflora f. immaculata Hort. has white flowers, with a greenish-white lip that is devoid of the coloured marks on the typical species.

The lip of Ds. uniflora has a rather deep incision on each side, which distinctly separates the midlobe from the side lobes. Its characteristic, large ovate side lobes overlap the midlobe, thus making the hypochile broader than the epichile. The long-lived flowers are not fragrant.

Distributed in Thailand, Vietnam, Peninsular Malaysia, Sumatra, Borneo, Sulawesi and the Philippines, Ds. uniflora is found between 600-700 m altitude. In the Philippines it grows often in full sun between 100-700 m elevation. A warm to intermediate-growing species, Ds. uniflora requires a well-drained medium, and bright light such as about 70% shade, with good air circulation at all times. Water it frequently during the warmer months, and give it a slightly drier winter rest. However, do not allow it to dry out for long periods. Rainfall in its natural habitat is heavy throughout the year.

References:

Baker, M.L. & C.O. Baker. (1996) Orchid Species Culture – Dendrobium. Timber Press, Portland, Oregon.

Clements, M.A. (2003) “Molecular Phylogenetic Systematics in the Dendrobiinae (Orchidaceae), with Emphasis on Dendrobium section Pedilonum.” Telopea, 10 (1): 247-298.

Clements, M.A. & D.L.Jones. (2002) “Nomenclatural Changes in the Dendrobieae (Orchidaceae) 1: The Australasian Region.” Orchadian 13 (11): 484-497.

Comber, J.B. (2001) Orchids of Sumatra. Natural History Publications, Kota Kinabalu, Borneo.

Cootes, J. (2001) The Orchids of the Philippines. Times Editions, Singapore.

Fessel, H.H. & P. Balzer. (1999) A Selection of Native Philippine Orchids. Times Editions, Singapore.

Karasawa, K. (1986) Orchid Atlas. Vol.4 – Dendrobium & Bulbophyllum. Chuo University Press, Tokyo.

Seidenfaden, G. (1985) “Orchid Genera in Thailand XII – Dendrobium Sw.” Opera Botanica. Council for Nordic Publications in Botany, Copenhagen.

Seidenfaden, G. & J.J. Wood. (1992) The Orchids of Peninsular Malaysia and Singapore. Olsen & Olsen, Fredensborg, Denmark.