Description
Dendrobium species are either epiphytic, or occasionally lithophytic. They have adapted to a wide variety of habitats, from the high altitudes in the Himalayan mountains to lowland tropical forests and even to the dry climate of the Australian desert.
This genus of sympodial orchids develop pseudobulbs, which vary in length from under a centimetre (e.g. Dendrobium leucocyanum) to several metres long (e.g. Dendrobium discolor), resembling canes. A few grow into long reedlike stems. Leaf bases form sheaths that completely envelope the stem. In the section Formosae (e.g. Dendrobium infundibulum), the sheaths and undersides of leaves are covered with fine short black hairs. Other species (e.g. Dendrobium senile), are covered with fine white hairs.
In selected species, the short, ovate leaves grow alternately over the whole length of the stems, in others, the leaves are bunched towards the apex of the stem (e.g. Dendrobium tetragonum). The axillary inflorescence vary in length from insignificant to 1m long, and can carry from a few (1-4) (e.g. Dendrobium nobile) to as many as 100 (e.g. Dendrobium speciosum) flowers. Deciduous species carry their leaves for one to two years then typically flower on leafless canes, while canes of evergreen species usually flower in the second year and can continue to flower for a number of years (e.g. Dendrobium densiflorum).
These orchids grow quickly throughout summer, but take a rest during winter. Dormant buds erupt into shoots from the base of the pseudobulb mainly in spring, and a few species in autumn. This is then followed by rapid growth of new roots. Reproduction is usually through seed, but a few species reproduce asexually through keikis produced along the stem, usually after flowering and sometimes as a result of injury to the growing tip.
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