Dendrobium is a very large genus of orchids with a very diverse species, perhaps only rivaled by the bulbophyllum genus. Most grow epiphytically on trees with a few growing lithopytically. All can be cultured in pots or mounted on cork or treefern slabs. Some species are deciduous while others are evergreen. Many require a dormancy period.
There are over 1,500 different species of Dendrobiums, and taxonomists are reclassifying them all the time. The genus is very diverse and offers a wide range of options for the grower, from the more familiar looking D. nobile and D. densiflorum to the weird, twisted shaped flowers of D. spectabile. Growing species can be a little more difficult than hybrids, but is very rewarding and leads to a deeper understanding of the genus as a whole.
The majority of the Dendrobiums for sale in garden stores are hybrids that have been bred for their ease of growing, flower size, flower color patterns and the number of flowers the plant can potentially produce. A plant can have anywhere from 10 to 100 flowers depending on its size and overall health. Most of these are "nobile" types, meaning they originally derived from cross breeding D. nobile and closely related species. Other popular hybrid types include antelope types and phalaenopsis types.
Many people would classify D. nobile types as cool growing because they need a winter rest period and drop in temperature, however most of the year intermediate temperatures are OK This group is mostly comprised of the miniature species that come from areas like New Guinea where a cloud cover is normal along with cool nights. They particularly thrive in the cooler parts of warmer climates.
Intermediate temperatures for orchid growing are about 50 to 55 F during the nights, and 75 to 85 F during the days. Many Dendrobiums fit this category, although some intermediate growers like a little more of a dip in the night temperature during the dormancy season to initiate flowering. This group is composed mostly of the Formosae types including, D. formosum, D. draconis and D. bellatulum, and a few odd species such as D. linguiforme.
Warm growing Dendrobiums (60 to 65 F nights, 75 to 90 F days) require more heat than other types and often do not always require rest periods. They include the Phalaenopsis and antelope types such as D. affine, D. bigibbum, D. antennatum and D. discolor. These are generally the species used to create many of the modern hybrids that are not nobile types. The hybrids derived from the warm growers should be treated as warm growers as well.