The following article was written for the Orchid Species Bulletin published by the Orchid Species Society,which is based in Brisbane, Queensland in June 2009.
Bear in mind that any cultivation notes refer to the subtropical conditions of Southern Queensland, Australia.
Bulbophyllum rufinum Rchb.f. was described by Heinrich Gustav Reichenbach in Orchidaceae in 1881. The specific epithet comes from the Latin rufus (dull yellowish or brownish-red) and the suffix –inus (indicating possession or resemblance) for the colour of the flowers. Bulb. rufinum has oblong, 4-angled pseudobulbs that are up to 5 cm long, and are borne along a creeping rhizome. At the apex of each pseudobulb is a single oblanceolate leathery leaf that is up to 25 cm long, which is borne on a petiole (stalk) that is up to 10 cm long. Long stiff decurved racemes that are 15-25 cm long, bearing 2-3 large basal sheaths are produced from the base of the matured pseudobulb. These carry well-spaced flowers that are about 1 cm long and are yellow to yellow-green, marked with purple to red-brown streaks.
Variable in colour the flowers may be nearly pure yellow to marked with much purple to red-brown. In addition the rachis varies from light green to purple. The blooms are subtended by white lanceolate bracts that are twice as long or more, as the pedicel plus ovary.
Distributed in Thailand, Myanmar, Laos, Vietnam and Cambodia, Bulb. rufinum usually grows on trees in deciduous forest. The habitat usually experiences a prolonged dry season. It is a tough species that will tolerate brighter light, particularly during its cool rest period. To accommodate its creeping habit Bulb. rufinum is best grown in a shallow tray or basket with a well-drained medium, or mounted. It can be mounted on cork bark, hardwood or tree fern, but may need daily watering or misting during the warmer months. Grow it under 70% shade and water it regularly while it is actively growing. Maintain high humidity with good air circulation. During the winter and when Bulb. rufinum is not actively growing, reduce the watering frequency but do not allow the plant to remain dry for long periods. Occasional misting or watering in the morning of sunny days will prevent the pseudobulbs from shrivelling. I recommend a winter minimum of 12oC.