Dendrochilum macranthum

The following article was written for the Orchid Species Bulletin published by the Orchid Species Society, which is based in Brisbane, Queensland in April 1999, and updated in March 2024.
Bear in mind that any cultivation notes refer to the subtropical conditions of Southern Queensland, Australia.

Dendrochilum macranthum Schltr. was first described by Rudolf Schlechter in Repertorium Specierum Novarum Regni Vegetabilis in 1911. The specific epithet comes from the Greek macro (large, great), and anthos (flower), referring to the size of its blooms, which when described were the largest of the genus.

Henrik Pedersen subsequently reduced Ddc. macranthum to Ddc. latifolium Lindl. var. macranthum (Schltr.) H.Æ.Pedersen, in Opera Botanica in 1997. Pedersen published this, after concurring with Oakes Ames’ observation that this taxon was very closely related to Ddc. latifolium. In fact, Pedersen was unable to find features other than the conspicuously different cataphylls (tubular sheaths) to distinguish the two taxa.

Plants of the World Online [POWO] recognises Ddc. macranthum as Coelogyne latifolia (Lindl.) M.W.Chase & Schuit. var. macrantha (Schltr.) M.W.Chase & Schuit. I prefer a consistent taxonomic treatment of Orchidaceae that does not rely predominantly on DNA sequence data. A more useful classification does not ignore plant habit, floral morphology, ecology, pollination syndrome, as well as breeding behaviour.

I follow David Banks and Jim Cootes (2011) who believe that Ddc. macranthum is a distinct species from Ddc. latifolium. Most plants of Ddc. macranthum in cultivation have been erroneously labelled as Ddc. magnum Rchb.f. Ddc. macranthum is an easy-to-grow and flower species, and is in fact quite commonly cultivated. Plants in cultivation may also be incorrectly labelled as Ddc. cobbianum Lindl., the name often given it by Philippine nurseries.

Ddc. macranthum has been written up and illustrated by David Banks and Jim Cootes as Ddc. magnum in Orchids Australia (1995), which is a different taxon that has odourless or only faintly scented flowers. Jim Cootes (pers. comm.) has never seen live plants of Ddc. magnum in Australia.

Ddc. macranthum produces many, long, pendent racemes during autumn, which have golden-orange blooms that have a strong, spicy scent. Ddc. latifolium flowers three months earlier in summer, and bears greenish-yellow flowers, with a brown lip, which are scented like chocolate.

Ddc. macranthum is a sympodial, epiphytic plant, which produces clustered, spindle-shaped to somewhat reverse pear-shaped pseudobulbs that are 2-7.5 cm long and 5-18 (-25) mm in diameter. Initially, the pseudobulbs are covered with 4-6 inflated, green sheaths that eventually dry and disintegrate into fibres. At the time of flowering, these cylindrical sheaths are already torn at the top, producing dark 5 mm triangular teeth – one of the distinguishing features of this species. Each pseudobulb carries a single, stalked, terminal leaf, with a basal stalk that is 3-25 cm long. The linear to broad, lance-shaped leaf blade is 13-60 cm long and 4-8 cm across.

Inflorescences are produced from the centre of the newly developing growth. The racemes of Ddc. macranthum have a suberect to slightly curved peduncle that is 12-52 cm long, and a pendent rachis that is 13-39 cm long. Its rachis carries numerous (up to 80) strongly scented flowers that are 12-18 mm across, which are borne in two ranks. The flowers of Ddc. macranthum are subtended by large cream to yellow-green floral bracts that cover the ovary and back of the bloom. When viewed from the side, the floral bract with the protruding sepals and petals remind David and Jim of an armadillo in profile. The flowers have green to golden-orange sepals and petals, and a darker brownish lip. Often, the flowers open a lighter green or yellow colour, and darken to orange or bronze with age.

Ddc. macranthum is found growing usually on trees in mossy forests from 1,200-1,630 m altitude. It is an intermediate-growing species that is endemic to Luzon and the Visayas in the Philippines. Plants can soon become large-sized specimens in very little time, if conditions are to its liking.

Shading of 60-70%, moist conditions at most times of the year, and excellent air circulation are the main requirements for Ddc. macranthum. During the warmer months of the year regular watering, and fertiliser can be given. In winter, while the plant is not so actively growing, a cooler, drier rest should be given, with sufficient water to prevent the pseudobulbs shrivelling. Plants should not be allowed to remain dry for prolonged periods. Ddc. macranthum seems to do well without the need for winter heating in areas as far south as Sydney. I recommend a winter minimum of 10-12 ⁰C. Lower temperatures are fine for short periods, provided that plants are dry at night; perhaps with some overhead protection.

References:

Banks, D.P. & J. Cootes. (1995). “The Genus Dendrochilum – A Guide to the Species in Cultivation: Part 2.” Orchids Australia, 7 (4): 57-59.

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

Cootes, J. (2011) Philippine Native Orchid Species. Katha Publishing Company Inc., Quezon City, Philippines.

Pedersen, H.Æ. (1997). The Genus Dendrochilum (Orchidaceae) in the Philippines – a Taxonomic Revision. Council for Nordic Publications in Botany, Copenhagen.