Bulbophyllum is a genus of mostly epiphytic and lithophytic orchids in the family Orchidaceae. It is the largest genus in the orchid family and one of the largest genera of flowering plants with more than 2,000 species, exceeded in number only by Astragalus. These orchids are found in diverse habitats throughout most of the warmer parts of the world including Africa, southern Asia, Latin America, the West Indies, and various islands in the Indian and Pacific Oceans. Orchids in this genus have thread-like or fibrous roots that creep over the surface of trees or rocks or hang from branches. The stem is divided into a rhizome and a pseudobulb, a feature that distinguished this genus from Dendrobium. There is usually only a single leaf at the top of the pseudobulb and from one to many flowers are arranged along an unbranched flowering stem that arises from the base of the pseudobulb. Several attempts have been made to separate Bulbophyllum into smaller genera, but most have not been accepted by the World Checklist of Selected Plant Families.
Description Plants in the genus Bulbophyllum are epiphytic or lithophytic sympodial herbs with thread-like or fibrous roots that creep over the surface on which they grow. The stem consists of a rhizome and a pseudobulb, the latter with one or two usually fleshy or leathery leaves. The flowers are arranged on an unbranched raceme that emerges from the pseudobulb, usually from its base. The dorsal sepal is free from the lateral sepals which themselves may be free or fused to each other. The petals are also free from each other and smaller than the lateral sepals. The labellum is often fleshy, curved and hinged to the base of the column.
Distribution and habitat The center of diversity of this genus is in the montane forests of Papua New Guinea (more than 600 species) which seems to be the evolutionary homeland, though the genus is pantropical and widespread, occurring in Australia, Southeast Asia (with over 200 species in Borneo), India, Madagascar (with 135 species, some endemic), Africa and in tropical central and South America.
The erect to pendent inflorescence arises laterally from the base of the pseudobulb. The flower form has a basic structural blueprint that serves to identify this genus. But this form can be very diverse: compound or single, with few to many flowers, with the resupinate flowers arranged spirally or in two vertical ranks. The sepals and the petals can also be very varied : straight or turned down, without footstalk or with a long claw at the base. They are often hairy or callous. There are two to four hard and waxy pollinia with stipes present or absent. The fruits are beakless capsules.
Taxonomy and naming The genus Bulbophyllum was first formally described in 1822 by Louis-Marie Aubert du Petit-Thouars in his book Histoire particulière des plantes orchidées recueillies sur les trois Iles Australes d'Afrique, de France, de Bourbon et de Madagascar in which he described eighteen species of Bulbophyllum.
There are now more than 2,800 records (accepted names and synonyms) for this genus. This large number and the great variety of its forms make the genus a considerable challenge for taxonomists: 120 sections and subgenera have been listed.
The genus name (Bulbophyllum) is derived from the Greek bolbos meaning 'bulb' and phyllon, 'a leaf', referring to the pseudobulbs on top of which the leaf grows.
In 2014, Alec Pridgeon and others proposed merging the genus Drymoda with Bulbophyllum in the Genera Orchidacearum and the change is accepted by Plants of the World Online and the World Checklist of Selected Plant Families. The former species of Drymoda included D. digitata (now B. digitatum), D. gymnopus (now B. gymnopus), D. latisepala (now B. capillipes), D. picta (the type species of Drymoda, now B. drymoda), and D. siamensis (now B. ayuthayense).
Evolution and biogeography Molecular phylogenetic studies place the origin of the orchid genus Bulbophyllum into the early Miocene. Biogeographic analyses and ancestral area reconstructions identified the Asia-Pacific region as the ancestral area of Bulbophyllum and suggest an early-to-late Miocene scenario of 'out-of-Asia-Pacific' origin and progressive (east-to-west) dispersal-mediated diversification, resulting in three additional radiations in Madagascar, Africa and the Neotropics, respectively.Gamisch, A., Comes, H.P. Clade-age-dependent diversification under high species turnover shapes species richness disparities among tropical rainforest lineages of Bulbophyllum (Orchidaceae). BMC Evol Biol 19, 93 (2019). https://doi.org/10.1186/s12862-019-1416-1
Sections
In 2019 Bulbophyllum were separated into four clades Neotropics, Africa, Madagascar, and the Asia-Pacific.
Africa Clade Image Section Type species Bifarium Bulbophyllum bifarium Carnosisepala Bulbophyllum carnosisepalum Chaseela Bulbophyllum pseudohydra Comata Bulbophyllum comatum Denticulata Bulbophyllum denticulatum Genyorchis Bulbophyllum apetalum GilgianaBulbophyllum gilgianum Megaclinium Bulbophyllum falcatumPtiloglossum Bulbophyllum barbigerum Oreonastes Bulbophyllum oreonastes
Madagascar Clade Image Section Type species Alcistachys Bulbophyllum occlusum BifalculaBulbophyllum implexumBulbophyllumBulbophyllum nutans Elasmotopus Bulbophyllum oxycalyx Ikongoense Bulbophyllum ikongoense InversifloraBulbophyllum cardiobulbum Kinethrix Bulbophyllum mirificum Lichenophylax Bulbophyllum lichenophylax Lupulina Bulbophyllum occultum Lyperocephalum Bulbophyllum lyperocephalum Moratii Bulbophyllum moratii PachychlamysBulbophyllum pachypus PantoblepharonBulbophyllum pantoblepharon PloiariumBulbophyllum coriophorum Polyradices Bulbophyllum petrae
Neotropical Clade Image Section Type species Bulbophyllaria Bulbophyllum bracteolatum Didactyle Bulbophyllum exaltatum Furvescentia Bulbophyllum nagelii Micranthae Bulbophyllum micranthum Napelli Bulbophyllum napellii Xiphizusa Bulbophyllum chloropterum
Asia-Pacific Clade Image Section Type species Acrochaene Bulbophyllum kingiiAdelopetalum Bulbophyllum bracteatum Aeschynanthoides Bulbophyllum dryas Altisceptrum Bulbophyllum elongatumAntennataBulbophyllum fuscopurpureum Balaenoidea Bulbophyllum balaeniceps Beccariana Bulbophyllum beccarii Biflorae Bulbophyllum biflorum Biseta Bulbophyllum bisetum BlepharistesBulbophyllum blepharistes Brachyantha Bulbophyllum umbellatum Brachystachyae Bulbophyllum repens Brachypus Bulbophyllum maxillarioides Cirrhopetaloides Bulbophyllum longissimum Cirrhopetalum Bulbophyllum longiflorumCodonosiphon Bulbophyllum codonanthumCodonosiphonBulbophyllum raulersoniaeDesmosanthesBulbophyllum croceum Drymoda Bulbophyllum drymodaEpicranthes Bulbophyllum epicranthes Ephippium Bulbophyllum lepidum Eublepharon Bulbophyllum eublepharon GongorodesBulbophyllum digitatum Hemisterantha Bulbophyllum hemisterranthum Hirtula Bulbophyllum hirtulum Hoplandra Bulbophyllum restrepia Hyalosema Bulbophyllum grandiflorum Hymenobractea Bulbophyllum infundibuliforme Intervallatae Bulbophyllum attenuatum Imitatores Bulbophyllum imitatorIone Bulbophyllum roseopictumLemniscataBulbophyllum lemniscatum LeopardinaeBulbophyllum leopardinum LepanthantheBulbophyllum lepanthiflorum Lepidorhiza Bulbophyllum amplebracteatumMacrocauliaBulbophyllum ovalifoliumMacrouris Bulbophyllum macrourum Minutissima Bulbophyllum minutissimum Monanthaparva Bulbophyllum striatellum Monanthes Bulbophyllum tortuosum Monomeria Bulbophyllum crabro MonosepalumBulbophyllum muricatum OxysepalaBulbophyllum clandestinum Papulipetalum Bulbophyllum papulipetalum Pedilochilus Bulbophyllum papuanum Pelma Bulbophyllum absconditumPeltopus Bulbophyllum peltopus Phreatiopsis Bulbophyllum phreatiopsePhysometra Bulbophyllum physometrum Planibulbus Bulbophyllum planibulbe PiestobulbonBulbophyllum piestobulbon Plumata Bulbophyllum plumatum Polymeres Bulbophyllum tenuifolium PseudopelmaBulbophyllum pseudopelma Racemosae Bulbophyllum careyanum RhinantheraBulbophyllum wrayi Saurocephalum Bulbophyllum saurocephalum Schistopetalum Bulbophyllum schistopetalum SerpenticaulisBulbophyllum wolfeiSestochilosBulbophyllum lobbii Stachysanthes Bulbophyllum gibbosum TapeinoglossumBulbophyllum centrosemiflorum Trias Bulbophyllum oblongum Tripudianthes Bulbophyllum tripudians Uncifera Bulbophyllum ochroleucum
Ecology
Pollination Many Bulbophyllum species have the typical odor of rotting carcasses, and the flies they attract assist in their reproduction through pollination. Nevertheless, some species with mild and pleasant floral fragrance attract Dacini fruit flies (particularly Bactrocera and Zeugodacus species) via methyl eugenol, raspberry ketone or zingerone that also act as floral reward during pollination.
To facilitate pollinarium removal and pollinia deposition, this group of orchids, particularly those that attract Dacini fruit flies, possesses a highly modified dynamic lip mechanism - either hinged or see-saw or spring lip (kept either in a close- or open-position depending on resupinate or non-resupinate flower, respectively). When an attracted fly has aligned itself to the opened lip, further probing, feeding and movement towards the lip base result in the lip to snap close, thereby, forcibly tipping the fly in to the column cavity to initiate pollinarium removal or pollinia deposition.Tan, K. H. 2009. Fruit fly pests as pollinators of wild orchids. Orchid Digest, 73(3): 180-187.Tan, K.H. and Nishida R, 2015 Pollination of bactrocerophilous Bulbophyllum Orchids. pp. 273-279. Proceedings of the 20th World Orchid Conference, Singapore, 2011. Singapore Botanic Gardens.Tan, K.H. and Tan, L.T. (2018) Movements of floral parts and roles of the tooth on column wall of Bulbophyllum praetervisum (Orchidaceae) flower for pollination by Dacini fruit flies (Diptera: Tephritidae). Journal of Pollination Ecology, 24(17): 157-163.
Use in horticulture Bulbophyllum (abbreviated Bulb. in the horticultural trade)Alphabetical List of Standard Abbreviations for Natural and Hybrid Generic Names, Royal Horticultural Society, 2017. includes species that have been the focus of orchid collectors for over a century. The plants require high humidity combined with good air movement and most of them are ever-blooming - flowering continuously throughout the year. They grow best at moderate light levels, but do not thrive in deep shade. They are considered moderate-to-difficult to cultivate, and require a controlled growing environment to achieve some degree of success. They are not typically suitable as houseplants, and most will not thrive in a Wardian case unless they receive adequate air movement.
The plants' growth habit produces widely spaced pseudobulbs along cord-like rhizome sections, and most of these plants are best accommodated on plaques. Some species in this genus can get very large, but most are small to medium-sized epiphytes from warm, moist, humid tropical forests. They can grow continuously year round with no apparent dormancy period if they are kept warm, are moderate feeders in cultivation, and must be kept moist all the time. They can tolerate dryness for short periods, but they have fine root systems which require moist conditions all the time.Illustrated Encyclopedia of Orchids
Some of the smaller species do well in pots with small-diameter bark substrate. The plants produce very fine roots generally, and the roots are easily damaged. The plants react poorly to disturbance of their roots. They are easy to maintain once a good environment is established with high humidity and a fresh, buoyant, lightly circulating atmosphere being critical. Most of these species cannot tolerate cold temperatures or freezing.