Dendrobium is one of the largest genera in the orchid family (Orchidaceae), encompassing roughly 1,600 tropical and subtropical species, with some authorities — including the American Orchid Society — citing the smaller figure of about 900. The genus was first described in 1799 by the Swedish botanist Olof Swartz, and is placed in subfamily Epidendroideae, tribe Malaxideae, subtribe Dendrobiinae. Its members are sympodial herbs, meaning each season's growth arises as a new shoot from a horizontal rhizome rather than continuing from a single apex.
The most distinctive feature of the genus is its pseudobulbs — water-storing stems that, when present, are typically hard and narrow, segmented, and often cane-like in shape; in some species they are cylindrical or cone-shaped, and a minority of species lack them altogether. Leaves are arranged in two ranks along the pseudobulb and range from terete and grass-like to broad and oblong; depending on the species they may be evergreen or deciduous. Horticulturally the genus is often split into two practical groups: "hard-cane" types with erect, evergreen pseudobulbs and "soft-cane" types whose thinner canes shed their leaves before flowering.
Flowers vary enormously across the genus. A single inflorescence may carry anywhere from one to many blooms, which can be resupinate or non-resupinate and span colours from white and green through yellow to pink and purple. Many species are fragrant. This diversity of flower form, colour and growth habit — together with the genus's wide geographic spread from the Himalayas to the Pacific — is a large part of why Dendrobium has become one of the most heavily hybridised orchid groups in cultivation, abbreviated "Den." in registered hybrid names.
Etymology
The genus name Dendrobium combines the ancient Greek words dendron ("tree") and bios ("life"), a reference to the genus's predominantly epiphytic habit — most of its species live perched on the trunks and branches of trees rather than in soil.
Distribution
Dendrobium has one of the broadest natural ranges of any large orchid genus. Wikipedia describes the genus as occurring throughout much of south, east and southeast Asia — including China, Japan, India, the Philippines, Indonesia, Vietnam, New Guinea and Australia — as well as on many of the islands of the Pacific. NC State Extension summarises the range as extending from India, China and Japan to Australia, New Zealand and New Caledonia, while the American Orchid Society describes a continuous distribution from India to the islands of the Pacific Ocean.
Ecology
Most Dendrobium species are epiphytes that grow on the trunks and branches of trees, with a smaller number living as lithophytes on rocks and a few as terrestrials. The genus is ecologically versatile, with species adapted to habitats ranging from high-elevation forests in the Himalayas to humid lowland tropical forests at sea level. This altitudinal span is reflected in the cultivation literature, which routinely distinguishes warm-growing lowland species, intermediate-temperature species and cool- to cold-growing montane species, each with distinct seasonal cycles tied to their native climates.
Cultivation
Dendrobiums are popular but demanding houseplants because the genus is so culturally diverse — different species need substantially different conditions. As a general rule plants want bright, indirect light (NC State Extension suggests around 2,000–5,000 foot-candles, ideally in a west- or south-facing window) and high humidity of about 60% or more, with good air circulation to prevent rot. A bark-based orchid mix is the standard potting medium; it should dry partially between waterings but never go bone dry. Weekly feeding with a specialist orchid fertilizer during active growth is typical.
Temperature and watering must be matched to the species type. Evergreen, tropical lowland Dendrobiums prefer warm temperatures and steady watering through the growing season. Deciduous, montane species — including many of the celebrated soft-cane hybrids derived from D. nobile — need a distinct cool-to-cold dry rest after their canes mature. Skipping this rest causes the plant to produce keikis (vegetative plantlets along the cane) instead of flower buds, and feeding with nitrogen during dormancy has the same effect.
Propagation
The American Orchid Society notes that deciduous-type Dendrobiums whose canes are not dried off after maturation tend to produce keikis — small plantlets that develop along the cane — instead of flowers. These keikis, once they have formed their own roots, are a routine vegetative propagation method for the genus: they can be detached and potted separately to produce genetically identical clones of the parent plant.
Cultural Uses
Dendrobium has a long history of human use across its Asian–Pacific range. Dendrobium nobile in particular is recognised as one of the 50 fundamental herbs of traditional Chinese medicine. The genus also carries strong symbolic and civic associations: several Dendrobium species or hybrids are official floral emblems — including Queensland (D. bigibbum / Cooktown orchid), Sikkim, Thailand, North Korea and Indonesia — and Singapore featured a number of Dendrobium hybrids on its Orchid Series of banknotes circulated between 1967 and 1976. In horticulture the genus is one of the most extensively hybridised in the orchid family, with registered hybrid names conventionally abbreviated "Den." by the Royal Horticultural Society.
History
The genus was established in 1799 by the Swedish botanist and taxonomist Olof Swartz, in Nova Acta Regiae Societatis Scientiarum Upsaliensis. Swartz's authorship is preserved in the standard botanical citation "Dendrobium Sw.", and the type species he designated for the genus is Dendrobium moniliforme.
Taxonomy Notes
Dendrobium sits in subfamily Epidendroideae, tribe Malaxideae, subtribe Dendrobiinae, within the family Orchidaceae. Estimates of how many species the genus contains vary by source: Wikipedia and NC State Extension cite approximately 1,600 accepted species, while the American Orchid Society gives a more conservative figure of about 900. GBIF currently records 2,328 descendant names under the genus, a figure that includes infraspecific taxa and unresolved synonyms. Within Dendrobium, orchidologists recognise a number of well-defined sections — including Latouria, Spatulata, Ceratobium, Formosae and Phalaenanthe — each grouping species with broadly similar morphology and cultural requirements. Hard-cane and soft-cane are informal horticultural categories rather than formal taxonomic divisions.
