Dendrobium Sw.,
Nova Acta Regiae Soc. Sci. Upsal. 6 (1799) 82
Very small to large sympodial epiphytic or terrestrial plants, with or without distinct rhizomes. Pseudobulbs present or absent, when present consisting of one to many internodes, short and thick to much elongated and slender, with one to many leaves; when absent stem elongated, slender, not fleshy, many-leaved. Leaves distichous, sheathing at the base or not, sheath sometimes hairy (hairs either blackish or white, not yellow or red-brown as in the genus Trichotosia), blade very rarely hairy, sometimes terete or laterally compressed, almost always deciduous, duplicate, leathery or sometimes stiffly thin-textured. Inflorescence lateral from the upper part of the stem, or terminal, a raceme or carrying a single flower. Flowers very small to large, resupinate or not, long-lived or ephemeral, often showy. Dorsal sepal almost always free from the lateral sepals, which are usually connate at the base, forming a distinct mentum (sometimes resembling a spur). Petals extremely variable, often fairly similar to the dorsal sepal, but in many species (e.g. most species of section Spatulata) widely different in size and shape. Lip without spur, usually not mobile. Column-foot present, usually longer than the column proper. Pollinia 4, solid, caudicles absent, stipe absent, viscidium absent.
Distribution
Sri Lanka, tropical continental Asia, Japan, Malaysia, Indonesia, the Philippines, Papua New Guinea, Australia, New Zealand, Pacific islands, east to Tahiti; about 900 species.
Distribution in the Philippines
Throughout the Philippines; about 85 species.
Habitat
Epiphytes in lowland and montane, deciduous and evergreen forest. Some species terrestrial in swampy places with sparse vegetation, in subalpine grassland, or on road banks.
Notes
Dendrobium is one of the largest orchid genera, in Asia surpassed only by Bulbophyllum. It is divided into more than 40 sections, of which 19 have representatives in the Philippines. In continental Southeast Asia the showy species belong predominantly to the sections Dendrobium (e.g. D. parishii Rchb.f.), Callista (e.g. D. chrysotoxum Lindl.) and Formosae (e.g. D. infundibulum Lindl.), but in the Philippines the section Calcarifera has the largest share of horticulturally significant species (e.g. Dendrobium victoriaereginae Loher). The millions upon millions of magenta Dendrobiums produced by the cut flower industry in Thailand and Singapore, adorning every hotel and restaurant in Southeast Asia, are hybrids of species originating from New Guinea and Australia. Many Dendrobium species are now very rare in the wild due to overcollecting and habitat destruction.
The huge number of generic synonyms testifies to the diversity of this genus, but the problem of deciding which clades 'really deserve' generic rank is in our opinion largely a matter of personal opinion and therefore not very interesting from a scientific point of view. The Linnean system of classification and naming is not capable, nor was it designed, to express every detail of a group's phylogeny. Splitting off ever finer twigs of the phylogenetic tree as seperate genera, as has been practised by various recent students of Dendrobium, does nothing to improve the system. It only creates nomenclatural instability, which defies one of the main purposes of the Linnean system. In our view, names should (in most cases) only be changed when they are demonstrably wrong. To give an exaggerated example: if somebody showed that Dendrobium anosmum is actually a Bulbophyllum that mimics a Dendrobium in almost every way, then there would be no alternative but to transfer D. anosmum to Bulbophyllum. Or to put it in technical terms: a genus should not be allowed to be polyphyletic. But for the sake of nomenclatural stability we should avoid splitting up an existing monophyletic genus into smaller monophyletic genera just because the cladograms or our instincts say that it can be done, since it can always be done. We could ultimately put every species in a genus of its own, and there would be no scientific argument against it.
The Philippine species of Dendrobium belong to the following sections: Aporum, Bolbodium, Breviflores, Calcarifera, Conostalix, Crumenata (syn. Rhopalanthe), Dendrobium, Distichophyllae, Dolichocentrum, Formosae (syn. Nigro-hirsutae), Fugacia (syn. Euphlebium), Grastidium, Latouria, Oxystophyllum, Pedilonum (syn. Oxyglossum), Platycaulon, Spatulata (syn. Ceratobium), Stachyobium, and Strongyle.