The Genus Dendrochilum
About the Genus
I have an interest in the genus Dendrochilum and even though I like all orchid genera it is this that I prefer due to their habit in the wild and look of the plants. I decided to create this website initially back in 2007 because of the very limited and often incorrect information available on the internet. Since writing the original website, a lot more literature has become digitalised making research thorough. The original website took two years to write and this version, part two, has taken 12 months. I have had a lot of valuable support from various people in getting this and the original website together, particularly with the use of their photos, feedback and encouragement. This is a website I hope you will all enjoy browsing through and will be helpful to aid you in more accurate identifications of the species belonging to this beautiful genus and interesting information about them.
However, before I go any further, I would like to state that I dedicate this website to the late Jeffrey Wood. Jeffrey offered me so much encouragement and an incredible amount of support, personal information and access to Kew’s archives while I was writing version one of this website. Furthermore, Jeffrey was an exceptional and dedicated taxonomist, admired by so many (including myself) and he particularly liked this genus.
What led me to set up the website initially, besides the love for this genus, was that I was frustrated with the amount of misinformation on the internet and in the horticultural trade which has changed with the rewrite of version two. I now find it poignant to record more about the ecology, biogeography, and pollination within the genus. The objective of this website is to act as a reference for this genus; to give users information about each Dendrochilum species and groups of species, to act as a resource and hopefully to raise more interest in this fascinating orchid genus. I have tried to gather as many original descriptions as I can and use them on this site. I am not a taxonomist and I often reference the works of Oakes Ames, Henrik Pedersen, Jim Comber, Jeffrey Wood, J.J Smith, Rudolf Schlechter and Gunnar Seidenfaden.
Within this website each species is listed alphabetically and has its own page. Each species is described with its full, currently accepted name, and accepted and recent infrageneric classification at the top of each page. I have tried to make each description as simple to read as possible. There is a glossary and leaf shape diagrams provided within this website to make the descriptions simple to read and to help understand the terminologies used.
There are at least 12 species which I believe may be conspecific with others. For some of these, I have not added a description and just a note stating the reasons why I believe they are conspecific, and that further investigation is required by a taxonomist.
Nomenclature and a Genera History
Dendrochilum belongs within the tribe Coelogyninae; other genera within this tribe include Pholidota, Pleione, Chelonistele, Coelogyne, Gymnadenia, Geesinkorchis, Gynoglottis, Entomophobia and Panisea.
Dendrochilum was first described in 1825 by C.L. Blume. He described 6 species that he found on Java and divided them into two sections. Following Blume’s original descriptions a few species were described during the 19th century mainly by Lindley and Reichenbach. These species are Dendrochilum filiforme in 1840, Dendrochilum glumaceum in 1841, Dendrochilum latifolium in 1843, Dendrochilum convallariaeforme in 1843, Dendrochilum tenellum in 1843 (as Acoridium tenellum), Dendrochilum uncatum and Dendrochilum pumilum in 1855, Dendrochilum longifolium in 1856, Dendrochilum brachyotum in 1857, Dendrochilum zollingeri in 1859, Dendrochilum magnum in 1863, Dendrochilum rhombophorum in 1877 (as Coelogyne rhombophora), Dendrochilum cobbianum in 1880 and Dendrochilum arachnites in 1882, Dendrochilum linearifolium in 1889. A number of collectors travelled through Borneo during the late 19th century and early 20th century, Odoardo Beccari, George Haviland, Henry Ridley, Mary and Joseph Clemens, these collectors discovered many more species which were then described by botanists. Once the US government took over the administration of the Philippines in 1898 a more comprehensive look at the Philippine flora began. E.D. Merrill and Oakes Ames added many more species to the overall list during the early part of the 20th century. Likewise in Sumatra J.J. Smith added many new species. L.O. Williams described many new Philippine species from the 1930s into the middle of the 20th century. During the later part of the 20th century many more Dendrochilum species were described by Henrik Pedersen, Jim Comber and Jeffrey Wood from herbarium specimens of unidentified species.
The first attempt at a monograph was made by J.J. Smith, in 1904, where 43 species were recognised. This was closely followed by Pfitzer and Kranzlin, in 1907, where 72 species were recognised. Oakes Ames took an interest in Dendrochilum and critically looked at the genus. During the first 25 years of the 20th century J.J. Smith transferred Platyclinis and Acoridium back into Dendrochilum. Oakes Ames then reinstated Acoridium as its own genus in 1906. Pfitzer and Kranzlin then reinstated Acoridium as a section of Dendrochilum in 1907 before Ames reinstated Acoridium again as its own genus in 1922. L.O.Williams finally transferred Acoridium back into Dendrochilum. These changes are reflected in the synonym list for many Philippine Dendrochilum species. For a very interesting read I would recommend the first part of Ames’ Illustrations and Studies in the Family Orchidaceae Fascicle 2. It appears that Ames sent some engravings of species he was about to describe to Dr. Engler for information only and to help Pftizer’s monograph on the Coelogyninae. Pfitzer passed away in the meantime and Kranzlin went on to describe Ames’s species sometimes using the wrong engraving. Later during the 20th century L.O. Williams took an interest in Dendrochilum and looked into section Acoridium and solved some taxonomic problems (Pedersen 1997). The last enumeration by Henrik Pedersen, Jim Comber and Jeffrey Wood was in 1997 where 270 species were recognised. Henrik Pedersen wrote a taxonomic revision of Philippine Dendrochilum in 1997, Jeffrey Wood wrote a taxonomic revision of Borneo Dendrochilum in 2001 and Henrik Pedersen wrote a checklist of east Malesian species in 1995.
As of June 2020, there are 300 accepted species of Dendrochilum and 318 if recognised varieties are considered.
The Dendrochilum genus is currently divided into two subgenera, which are:
Subgenera 1) Dendrochilum
Subgenera 2) Platyclinis
As there is an increase in phylogeny research, we are likely to see further changes to the structure of the genus and the number of species. At the beginning of 2020 a Phylogeny paper (Pedersen et al), resulted in the revision of the infrageneric classification of the genus and two subgenera are now being recognised. The study also revealed that Bracisepalum is deeply embedded within Dendrochilum and is now transferred to the latter genus to achieve monophyly.
Many new species continued to be described (Pedersen 2004) (Pedersen 2001) (Pedersen 2005) (Cootes 2009) (Cootes 2010), (Pedersen 2011), (Cootes, 2017). There are still unidentified plants in herbaria, and in hobbyist collections and of course in the wild. I do believe that further work needs to be undertaken by taxonomists to critically review recent newly described species as there are a few that are potentially conspecific with previously described species. Some species have been described without considering all known Dendrochilum species or for reasons which have not previously constituted allowing species rank within the rest of the genus.
Distribution
Dendrochilum are distributed in South East Asia, and mainly in a region known as Malesia. Dendrochilum can be found from Southern Myanmar and Thailand south through the Indonesian archipelago to New Guinea and north to the Philippines and Southern Taiwan. At the time of writing, the genus has its centre of speciation in the Philippines, Borneo and Sumatra. Jeffrey Wood wrote in 2001 that 91.9% of Bornean species are endemic to that island, of which 37.9% or 33 species are endemic to Mount Kinabalu alone (Wood 2001). Below is a table showing the distribution and % of endemism by island (as of June 2020)
A table showing the distribution and % of endemism by island (as of June 2020)
This table shows the distribution of the two subgenera where they are both known to occur together.
Most Dendrochilum are found in lower or upper montane forest. These two altitudinal zones contain mossy cloud forest which is a favoured habitat of many Dendrochilum species. Jeffrey Wood wrote “Many species seem to favour ridge-top shrubbery and mossy elfin forest which experience variable and often harsh conditions ranging from bright sunlight to dense cloud cover or drying winds. These localities experience a large fluctuation in temperature” (Wood 2001). Henrik Pedersen provided an exceptional breakdown of Philippine species within altitudinal zones, of which I will briefly outline.
Van Steenis recognised five altitudinal zones in Malesia,
The largest Philippine species lists are from mountains within the Southern Sierra Madre and Baguio area on Luzon. These mountains have been studied and collected extensively which could explain the larger numbers of Dendrochilum. Further study is needed within western Mindanao and on Palawan. New species are still being brought into cultivation and described from Mindanao. Unfortunately the political situation within western Mindanao and safety on Palawan keep many botanists away. Suitable habitat exists on Palawan and further species could be found there.
On Sumatra most species have been collected within the mountainous west and northern regions of the island. The centres of diversity in Sumatra are Mount Leuser National Park in Aceh Province and north of Lake Toba, the Mount Talang and Mount Kerinci areas. Further study is needed for the Sumatran species as there are undoubtedly conspecific species as well as new species to be described. Unfortunately some areas in Sumatra, such as Aceh Province are politically unstable and keep botanists away.
On Java most species have been found within the mountainous western part of the island. The rainfall is consistent throughout the year in the west. Eastern Java has a wet/dry season which is not suitable for most Dendrochilum species. There are a few poorly known Javan species which are almost unknown and exploration of their known habitat is needed. There are likely to be new species on Java.
On Borneo most species have been collected within the Crocker Range including Mount Kinabalu and Mount Trus Madi, Mount Pagon, Sabah’s Sipitang District, the Kelabit Highlands including Mount Murud, Batu Lawi, Mount Mulu, Apo Kayan, Mount Penrissen and its surrounding mountains. Jeffrey Wood wrote “Montane area of southern and east-central Sarawak and large portions of upland Kalimantan, which are probably rich in Dendrochilum, still remain where little or no collecting has taken place” (Wood 2001). Wood (2001) also wrote that the distribution patterns of Dendrochilum within Borneo correlate with the height of the cloud, local temperature (particularly minimum temperatures), exposure and forest type.
Presently there is only one species found in New Guinea, Dendrochilum longifolium. This has puzzled taxonomists because preferred habitat on that island is plenty. Jeffrey Wood wrote that the mycorrhizal relationships of many Dendrochilum species may be host specific and certain fungal partners could be absent in New Guinea (Wood 2001). Henrik Pedersen wrote an interesting piece on evolutionary interpretation (Pedersen 1997 p35) suggesting that the majority of Dendrochilum evolved after the Pleistocene which has resulted in higher endemism. The Malesian region is thought to have been cooler during the Pleistocene (van Steenis 1984) which would have seen Dendrochilum growing at lower elevation and therefore more widely dispersed at the present time. Cool growing alpine plants, such as most Dendrochilum, are currently restricted to high elevations on mountains. As mountains are seen as ‘islands’ within a sea of jungle for these alpine plants, dispersal would be much harder in a warmer climate. If most Dendrochilum have evolved after the Pleistocene most species would not have had the time to increase their geographical range.
This theory was updated early in 2020 in the Phylogeny paper by Pedersen et al. (2019). The study revealed that Dendrochilum evolved from the late Miocene and into the Holocene. The genus probably evolved in the Southern Philippines rather than west Sumatra as previously thought. However, more molecular sampling and analysis is needed to further support this theory (Pedersen et al 2019).
As more research is undertaken into pollination and phylogenetics within Dendrochilum, we will learn more about their history and diversification.
Morphology
Ed de Vogel suggested that Dendrochilum evolved from Pholidota section Acanthoglossum (De Vogel 1989).
When describing species on this website I have preferred to use the description format of Jeffrey Wood and Henrik Pedersen and I have added in words to make them readable for those not of a scientific background. Pedersen has used the terms describing the inflorescence of de Vogel (1988) and the structure of the column of F.N. Rasmussen (1986).
Dendrochilum are sympodial orchids that can have the following floral parts
Peduncle
Rachis
Bract
Dorsal sepal
Lateral sepal
Petals
Labellum
Column
Column foot
Apical wing
Stelidia
Keel/callus
Sympodial habit
There are two main types of sympodial habit found in Dendrochilum, the first are pendent and creeping plants that grow along an elongated and sometimes branching rhizome. The pseudobulbs are often spaced widely apart. The second growth habit is tufted plants where the pseudobulbs cluster together on short rhizomes.
The pendent and creeping plants are found in all species of the subgenus Dendrochilum and in many Sumatran species within subgenus Platyclinis. There are a couple of species within subgenus Platyclinis from Borneo. Jeffrey Wood wrote that species with the first type of growth habit are generally found in sheltered habitat and hang from trees, scramble over rocks or the forest floor as a terrestrial (Wood 2001). This is also observable for Sumatran species.
Cataphylls
New growths are covered by cataphylls while they are growing. The cataphylls disintegrate into persistent or non persistent fibres as the pseudobulbs mature. The presence of cataphylls at the time of flowering is of limited diagnostic or taxonomic value on a couple of species, for example Dendrochilum latifolium var latifolium and Dendrochilum latifolium var macranthum.
Pseudobulbs
Pseudobulb shape and size varies greatly between species. Some Bornean species of subgenus Platyclinis have orange, yellow, red and even red suffused with green coloured pseudobulbs.
Leaves
There are two types of phyllotaxis within Dendrochilum leaves; the leaves are either conduplicate or convolute. All Dendrochilum leaves are petiolate or nearly sessile. The subgenus Dendrochilum have the shortest petioles, some of the species are nearly sessile. The width of leaves can be of diagnostic importance within some species groups. Jeffrey Wood wrote that leaf width is of limited diagnostic value in Borneo taxa (Wood 2001). There are always distinct nerves any many indistinct nerves that run the length of the leaf, measuring the distance of the lateral nerves from the leaf margin can be of diagnostic value. The leaves generally have entire margins but minutely erose to undulate margins exist.
Some Bornean species within subgenus Platyclinis have crystalline calcium oxalate bodies on the leaf blades.
Abnormalities of bifoliate leaves have been recorded on Dendrochilum pallidiflavens (Pederson pers comm) and I’ve observed on one of my own plants (Dendrochilum septemnervium). I have a photo of Dendrochilum latifolium var macranthum with two leaves.
Inflorescence
There are three types of inflorescence found on Dendrochilum (Pedersen 1997).
Synanthous – the inflorescence grows from developing pseudobulbs and grows at the same time as the subtending leaf
Heteranthous – the inflorescence grows from the rhizome and does not go on to develop a new growth
Hysteranthous – the inflorescence develops after the leaf is fully developed.
Dendrochilum that have synanthous inflorescences and convolute leaves generally have the subtending leaf envelop the inflorescence to form a loose funnel. Dendrochilum that have synanthous inflorescences and conduplicate leaves have the peduncle free from the subtending leaf at the time of flowering. There are 11, probably 12 species from subgenus Acoridium section Acoridium where at least for a part the peduncle is enclosed by the subtending leaf, these species are; Dendrochilum graminifolium, Dendrochilum wenzelii, Dendrochilum javierianum, Dendrochilum saccolabium, Dendrochilum perplexum, Dendrochilum tenellum, Dendrochilum stenophyllum, Dendrochilum williamsii, Dendrochilum luzonense, Dendrochilum louisianum (Pedersen 1997), Dendrochilum pseudowenzelii (Pedersen 2011). The 12th species is probably Dendrochilum banksii.
The inflorescence is separated into a peduncle and a rachis. There are none or many non floriferous bracts at the proximal end of the rachis, these bracts separate the peduncle from the rachis. The inflorescence is either flexuose or has distichously alternating flowers. On some species such as Dendrochilum convallariaeforme and Dendrochilum propinquum the rachis twists to form a cylindrical spiral. The flowers open from either the proximal, central or distal part of the rachis, although most commonly from the proximal section. The point from where the flowers open can be of diagnostic value. Whether an inflorescence is lax or not is not of diagnostic importance (Dendrochilum lyriforme).
Floral bracts
Henrik Pedersen wrote that floral bracts rarely contribute as factors of taxonomic diagnostic value (Pedersen 1997) and for this reason I have chosen not to include them in the descriptions on this website.
Flowers
Most Dendrochilum have resupinate flowers (labellum facing downwards) but a couple of described species have non-resupinate flowers, Dendrochilum scriptum, Dendrochilum propinquum, Dendrochilum cupulatum, Dendrochilum tortile, and Dendrochilum muluense.
Flower colour is of little diagnostic value and even though the flower colour is given within this website it should not be the basis of identification.
There are always three petals on a Dendrochilum flower, the lateral petals and a ventral petal, for the purposes of this website I have called the ventral petal the labellum. The petals are generally shorter and narrower than the sepals and are much more inclined to have erose, irregular or fimbriate margins. The margins of the petals can be of diagnostic value.
There are always three sepals on a Dendrochilum flower, two lateral sepals and a dorsal sepal.
The sepals and petals are widely spreading, incurved or recurved. The sepals and petals are never bent at a right angle as they are in Pholidota. A couple of Borneo species within subgenus Platyclinis have petals that are twisted at 90 degrees from the vertical.
The labellum is either elastically or firmly attached to the column in subgenus Platyclinis. In Subgenus Dendrochilum it is elastically attached to the column. The way a labellum is attached to the column is of great diagnostic value. The labellum can be 3-lobed, entire, obscurely 3-lobed, pandurate, bilobed, hastate and cruciform. There are two species with a cymbiform labellum, Dendrochilum cymbiforme and Dendrochilum magnum, to a lesser extent. A couple of Philippine species have a saccate labellum. The labellum is usually porrect or pendent, can recurve, decurve or even coil as can be seen in the pictures of Dendrochilum simile. Many Dendrochilum have a concave labellum, one species, Dendrochilum zollingeri is of particular interest because the labellum is concave at its apex.
Most Dendrochilum have ornaments on the labellum in the forms of calli or keels. There are usually two keels found on the labellum within subgenus Dendrochilum (Pedersen 1997).
The labellum is one of the most important taxonomic diagnostic features within the genus. The shape of the labellum is of diagnostic importance but has not always been enough to separate a species (e.g. Dendrochilum longifolium, Dendrochilum philippinense, Dendrochilum quadrilobum, Dendrochilum filiforme etc). Dendrochilum philippinense and filiforme can have 3-lobed or entire labella.
Column
The column is the most important diagnostic feature within the genus Dendrochilum. When trying to identify a species, always try to get a close up image of the column.
There is always a column in every Dendrochilum flower. There is either no column foot, a short column foot, or a prominent column foot. A column foot is of important diagnostic value.
Within the subgenera Dendrochilum the apical hood is elongated, this varies in subgenus Platyclinis.
Jeffrey Wood wrote a fascinating paragraph on the stelidia “Anatomical examination by Pederson (1997) failed to find any vascular traces of staminoda in the stelidia of the Philippine D. cobbianum and D. filiforme. The functional and, admittedly limited, anatomical evidence points to the stelidia being derived character. Stelidia probably evolved only once in a common ancestor”
Within this website I do not describe the rostellum, stigmatic cavity, anther cap or pollinia.
There are stelidia in the subgenera Dendrochilum and either with or without in subgenus Platyclinis. The length, shape and position of the stelidia are of important diagnostic taxonomic importance but have not always been enough to separate or describe a new species (e.g. Dendrochilum meijeri)
Dendrochilum in Cultivation
There are only a fraction of Dendrochilum species found in cultivation and information about the specific habitat of many of them is hard to find or not known. A great article for general Dendrochilum culture was written by Jim Cootes and David Banks in Orchids Australia, 1995.
What most growers of Dendrochilum agree is that:
There should be plenty of air movement
The plants should be kept moist and never be allowed to dry out
Watering should be from the bottom and not from above the plant
Humidity must be high
There needs to be a difference between day and night temperature
Water should have low salinity
In the wild many Dendrochilum species are found in exposed conditions including ridge tops, cliff tops, outer tree branches, rock faces and the tree canopy. This indicates that plenty of air movement is essential for cultivating these species, a summary that my experiences confirm.
Links to good articles about cultivation are in the resource/library section of this website
Identifying Dendrochilum
One thing I have found with this genus is that you should never assume identification unless you are absolutely sure and have ruled out all other possibilities by using recent published keys to the genus, the original description and a reliable drawing. I usually ask a Dendrochilum expert for their opinion even after establishing what I think the species could be. As I mentioned above, care needs to be applied if you are comparing your plant to a photo on the internet. Be careful of the accuracy of all photos found on Facebook, Instagram, online orchid encyclopaedias, photography sites, books, orchid society show tables, nursery catalogues and in particular plant lists from the Philippines. There are even awarded plants around the world that have been mis-labelled. Some Dendrochilum have a similar appearance and can only be easily identified from one another by minute features such as how far the lateral nerves are from the leaf margin, the position/shape of their calli, the keels, shape and margin type of the apical hood and the position of the stelidia. Some of these features can only be seen under a microscope or by a very powerful lens.
To help with any potential confusion each species page on this website comes with a similar species heading where you might want to check another similar looking species photo or plant description just to be sure. I have created labellum and column comparison images to help make identifications easier, accurate and to point out similarities between species.
Some species vary greatly, sometimes based on their natural demographics but sometimes this is just how they are. Species such as Dendrochilum wenzelii or Dendrochilum kingii have a variety of colour forms. Other species such as Dendrochilum glumaceum, Dendrochilum cornutum or Dendrochilum simplex can vary greatly in flower and plant size.
Some commonly mixed up species include Dendrochilum magnum with Dendrochilum latifolium var macranthum and Dendrochilum latifolium var latifolium. Several years ago, in the hobbyist trade, Dendrochilum wenzelii and Dendrochilum javierianum were frequently referred to Dendrochilum arachnites ‘red’ or ‘yellow’ a mistake perpetrated by Philippine orchid nurseries who import them to Australia, the USA and Europe. Even the odd herbaria have fallen for this particular mix-up. Dendrochilum cootesii is often mislabelled as Dendrochilum anfractum. Dendrochilum pangasinanense is often sold as Dendrochilum abbreviatum in Europe. Many other species are incorrectly identified on orchid encyclopaedias, Flickr and other sites because they are not validated by the site owners and photographers with the use of herbarium specimens and genera experts; this in turns leads to mis-labelled plants and photos in personal collections and misinformation about species.
Acknowledgements
There are a few people who have been very helpful with their information and contribution to this website and the knowledge contained within about the genus Dendrochilum.
Thank you to Henrik Pedersen for all of the personal correspondence, information, manuscripts, emails, encouragement and photos.
Thank you to the late Jeffrey Wood and the Royal Botanic Gardens, Kew for the personal correspondence, encouragement, guidance and for allowing me to use the bequeathed photos of the late Jim Comber, the images from the Orchids of Sumatra and the photos from the Dendrochilum of Borneo and the Orchids of Borneo series.
Thank you to Mark Arcebal K. Naive for the feedback and editing of this text for version two of this website. Thank you to Malcolm Perry and Jim Cootes for the feedback and editing of text for the original website. Thank you to Pete Carey for the support and encouragement in the early days of me working on version two of this website.
Thank you to Ed de Vogel and the team at the National Herbarium in the Netherlands for supplying me with manuscripts from the archives of the National Herbarium in the Netherlands.
Finally, thank you to the following people for the use of their personal photos for this website:
André Shuiteman
Andrew Pranada
Art de Vogel
Bill Temple
Chien C Lee
C. L Chan
Daniel Tennant
David Banks
David Basler and the Swiss Orchid Foundation
David D. Beadle
David Titmus
Dian Rahardjo
Eric Hunt
Francis Quesada Pallares
Gary Meyer
Gary Yong Gee
George Lai
Hans Schaibel
Henrik Pedersen
Jeffrey Champion
Jeffrey Tyler
Jim Cootes
John Varigos
Leicneagra Leic
Kai Squires
Kath Barrett
Kevin Moore
Mac Arthur Cababan
Malcolm Perry
Mark Arcebal K. Naive
Marni Turkel
Melanie Schori
Miguel David De Leon
Oscar Johnson
Paul Johnson
Peter Maxwell
Peter O’Byrne
Pieter Pelser
Peter Quakenbush
Rachmat Setiawan
Ravan Schneider
Renanta Prabata
Rene Alfred Buton Busamante
Rogier van Vugt
Ronny Boos
Ron Parsons
Ron Rayher
Thomas Karrer
Todd Barkman
Tom Ballinger
Tony Rodd
Wally Suarez