Bulbophyllum is the largest genus of orchids, and the third largest of all plant genera. It boasts over 1,800 species, though the genus is not uniformly documented, as many species have numerous synonyms. About 120 subgenera or sections have been postulated, and new species are discovered every year. Bulbophyllum species grow throughout the tropical world, but the center of diversity is in Papua New Guinea, home to over 600 Bulbophyllum species. Two Australian species formerly classified as Bulbophyllum became the two only members of the Oncophyllum genus, O. globuliforme and O. minutissimum, in 1961.
There is immense variety within Bulbophyllum. Plants belonging to the genus all have a type of storage structure between the leaves called a pseudobulb, with a single node. The flowers grow from the base of the pseudobulb and feature a mobile labellum or lip, a specialized structure among orchids that serves to attract insect pollinators and offer them a place to land.
Orchids in this genus may be succulents, creepers, or tall plants with stiff stems. Some species grow on other plants or on rock. Most species feature flowers with a smell of rotting meat to attract insect pollinators, often blowflies or carrion beetles. The color, size, and shape of the flowers also show great variety. Some Bulbophyllum flowers are hairy or rough to the touch.
B. beccarii, which grows in the rain forests of Borneo, forms large, cup-shaped leaves around the trunks of trees, which the plant uses to catch debris and convert it into fertilizer. B. medusae, or Medusa's Bulbophyllum, grows in Thailand and Borneo and features white flowers with numerous snake-like sepals, reminiscent of the hair of Medusa of Greek myth. The rare B. fletcherianum of Papua New Guinea, also called the Tongue Orchid, is one of the largest orchids in the world, with leaves reaching six feet (1.8 meters) in length.
Many Bulbophyllum species are rare or endangered. B. bifarium and B. jaapii, two vulnerable species, as well as the endangered B. modicum, are endemic to Cameroon. B. gravidum, growing in Cameroon and Equatorial Guinea, and B. bifarium, growing in Cameroon and Nigeria, are also vulnerable, while the endangered species B. pandanetorum grows in Cameroon and Gabon. B. rubrolabellum and B. tokioi are two endangered species native to Taiwan. The two critically endangered species, B. filiforme and B. kupense, both grow in Cameroon, with the former additionally growing in Nigeria.