Classification of Orchid Genera 2

This is part two of a compilation of five instalments that first appeared in the Nambour Orchid Society newsletter between June and October 2021.

Sobralia macrantha
(photo by W. Harris)

The sub-family Epidendroideae is by far the largest, accounting for 79%  of all accepted species. It contains 15 tribes, some of which contain only one or two genera and generally small numbers of species, and others with many species and thousands of genera. The first eight tribes listed in the Chase classification contain few species of interest to hobby growers. The exceptions are Epipactis (tribe Neottieae) with 49 species,  more popular in the northern hemisphere, and Sobralia (tribe Sobralieae), with 149 species widespread through Mexico, Central and  South America, popular in cultivation world-wide.

Coelogyne lentiginosa. Dendrochilum wenzelii
(photo by W. Harris) (photo by C. McMonagle)

The tribe Arethuseae contains two subtribes, Arethusinae and  Coelogyninae. Arundina is the genus of interest in Arethusinae. Subtribe Coelogyninae contains a number of genera of interest including Bletilla  (five species), Coelogyne (200 species), Dendrochilum (278 species), Pholidota (39 species), Pleione (21 species) and  Thunia (five species). Coelogynes are popular in cultivation and many species carry large  numbers of flowers.  

Dendrochilum is another genus popular in  cultivation, particularly in this region.  Tribe Malaxideae contains two sub-tribes.  The first is Dendrobiinae comprising the  two largest genera, Bulbophyllum (1867 accepted species at the time of the Chase classification, now over 2000) and Dendrobium (1509 species). Due to the large number of species in these genera, scientists have grouped species  having similar characteristics into Sections. There are 98 Sections in Bulbophyllum, distributed across four regions. There are 12 Sections in the African Region, 15 Sections in the Malagasy Region (Madagasgar and other islands in the Indian  Ocean), 67 Sections in the Asia/Pacific region and six Sections in Neo-tropical America (Tropical areas of Central and  South America, including the Caribbean Islands). If you noticed that the total is 100, it is because there are two Sections that occur in two regions. 

Bulb. rothschildianum Bulbophyllum lobbii ‘Murph’
(photo by W. Harris) (photo by C. McMonagle)

Bulbophyllums occur in tropical and temperate areas of all continents except Antarctica. The greatest concentration of  species is in New Guinea and 26 species are found in Australia,  all close to the east coast of Queensland and New South Wales.  There has been a marked increase in the cultivation of  Bulbophyllums in recent years, particularly amongst ‘Species’  growers. Forty-seven AOC awards  have been granted to  Bulbophyllums over the past 10  years. Bulbophyllum lobbii ‘Murph’, pictured right, was  awarded an FCC and an ACE by the AOC in 2010.  

The most significant change to  Bulbophyllum in the new classification was the transfer of around 300 species previously  described as Cirrhopetalum to Bulbophyllum. Trias was another smaller genus  transferred to Bulbophyllum. Bulb. rothschildianum, pictured right, is a species in the  section Cirrhopetalum.

Dendrobium is one of the most popular genera cultivated in tropical and sub-tropical regions. It occurs naturally in  India, China, Japan, all of the Asean countries, New Guinea, Australia, New Zealand and islands across the western  Pacific Ocean. There is a wide range of variation in vegetative and floral characteristics across the genus. The genus has  been grouped into 30 Sections, the more popular being Phalaenanthe, Dendrobium, Spatulata, Latouria, Dendrocoryne,  Calyptrochilus, Formosae, Cadetia and Diplocaulobium. Cadetia,  Diplocaulobium and Grastidium were separate genera prior to GO Vol 6  when they were absorbed into Dendrobium.  

Den. speciosum Den. bigibbum
(photo by C. McMonagle) (photo by W. Harris)

Section Phalaenanthe is  one of the smallest in the  genus with only two species but Den. bigibbum, pictured right, features in the parentage of over 11,000 hybrids. There are 12 species native to Australia in Section Dendrocoryne,  including Den. speciosum, pictured right. There are also 12 Australian species in Section Rhizobium, known for a  short time as genus Dockrillia but returned to Dendrobium in GO Vol 6, and 8 species in Spatulata. Smaller numbers of Australian species occur in 14 other Sections.  

Section Calyptrochilus is one of the largest numerically with 114 species native to New Guinea. Many species previously in Sections Oxyglossum and Pedilonum were transferred to Calyptrochilus. A popular species from this Section is Den. cuthbertsonii, pictured below. The so-called soft cane or Indian Dendrobiums are all in Section Dendrobium. Den. nobile, from this Section, features in the parentage of around 2700 registered hybrids. One of them is Den. Pink Doll, pictured below, was awarded an FCC and an ACM last year. Sections Latouria and Spatulata both contain around 50 species with the greatest concentration in New Guinea and adjacent islands. 

The remaining subtribe in Malaxideae is Malaxidiinae which contains the numerically large genera, Liparis with 426 species and Oberonia with 323 species. Liparis are found on all continents except Antarctica with many species occurring in Australia. They generally have large numbers of small flowers on an inflorescence and the labellum is usually the dominant feature. Liparis condylobulbon, pictured below, is native to Queensland and SE Asia, including New Guinea and is popular in cultivation. Oberonias, often called “Fairy Orchids”, also occur in many tropical and subtropical regions, including six species in Australia. Tiny flowers occur in large numbers on long inflorescences. Oberonia titania, pictured below, is one of the Australian  species.

Den. Pink Doll. Oberonia titania Liparis condylobulbon Den. cuthbertsonii
(photo by C. McMonagle) (photo by W. Harris) (photo by W. Harris) (photo by C. McMonagle)

Literature cited

Chase M. W., Cameron K. M., Freudenstein J. V., Pridgeon A. M., Salazar G., Van Den Berg C. and Schuiteman A., An updated classification of Orchidaceae, Botanical Journal of the Linnean Society, 177, 2015 151-174.

Pridgeon A. M., Cribb P. J., Chase M. W. and Rasmussen, F. N., Genera Orchidacearum, Vol 1 1999, Vol 2 2001, Vol 3 2003, Vol 4 2006, Vol 5 2010, Vol 6 2014, Oxford University Press.

Please note: Since the publication of this article the Coelogne species has been expanded. If you’d like to find out more about this change please refer to the article linked here: https://www.nambourorchidsociety.com/articles/expansion-of-coelogyne-species

Author: Charlie