Dendrobium is Asian and Australian genus, and also dwells on many Pacific Ocean islands. Dendrobium orchids grow naturally in diverse ecosystems – from warm rainforests to cold Himalayan mounts and dry Australian deserts. Given the fact that they live in so different biomes, Dendrobium is one of the most diverse orchid genera and because of it they are divided into different groups, according to their specific demands. They are divided to cold, intermediate and warm-growing, and they can also be divided to ones who need a cold dry rest period, and ones who do not need it.
The orchids that vendors sold are actually complex hybrids and some of this complex hybrids do not actually require such cold and dry dormancy, as they have some warm-group Dendrobiums in their pedigree. hybrids are much more easy to grow than species Dendrobiums, and within species, the warm group is easiest to grow.
Dendrobium nobile, Dendrobium phalaenopsis, and Dendrobium bigibbum are three popularly grown Dendrobium species which have been used extensively in hybridizing. These species and their hybrids are often added to collections without the grower being aware of their very different cultural requirements. We hope that a knowledge of the climatic conditions in the three habitats will help growers decide whether they can provide the conditions needed to grow and bloom these species and many of their hybrids.
A few general facts about the large and varied genus Dendrobium might help growers understand the difficulty in trying to apply generalizations to so many species. D. nobile was once used extensively in hybridizing with 77 hybrids registered in which it was a parent. The most commonly used parents in recent registrations, however, have been the Australian species D. phalaenopsis and the closely related D. bigibbum.
Cold Dendrobium species
Cold-growing species are Dendrobium wattii, Dendrobium wangliangii, Dendrobium vonroemeri, Dendrobium vexillarius, Dendrobium vannouhuysii, Dendrobium sutepense, Dendrobium sulphureum, Dendrobium subclausum, Dendrobium stellar, Dendrobium sinominutiflorum, Dendrobium sculptum, Dendrobium rupestre, Dendrobium putnamii, Dendrobium piranha, Dendrobium otaguroanum, Dendrobium cuthbertsonii. They cannot tolerate warmth for long periods of time and need to grow at cool all year round, as they are mostly mountain miniature to medium-sized species. The best way to grow them is mounting on slabs because at cool conditions roots are very prone to rotting. Mounting is the best way to keep roots of these Dendrobiums healthy.
The second group is intermediate growing Dendrobiums, such as Dendrobium kingianum, Dendrobium nobile, Dendrobium crassifolium, Dendrobium crassicaule, Dendrobium amethystoglossum, Dendrobium gnomus, Dendrobium harveyanum, Dendrobium loddigesii, Dendrobium longicornu. All of them prefer intermediate temperature, half to full sun and moderate watering. Some representatives of this group need cold and dry dormancy to develop flower buds. For instance, popular Dendrobium nobile, Dendrobium kingianum and Dendrobium loddigesii produce keikis instead of flowers if not provided with cool temperatures , but they prefer intermediate temperatures when they are vegetating.
Warm Dendrobiums species
The third group is so called warm Dendrobiums – well known Dendrobium phalaenopsis, Dendrobium speciosum, Dendrobium spectabile, Dendrobium tangerinum, Dendrobium taurinum, Dendrobium transparens, Dendrobium truncatum, Dendrobium unicum need warm grow conditions. Some of them such as Dendrobium phalaenopsis and spectacular Dendrobium spectabile need year-round hot to warm temperatures, but deciduous Dendrobium unicum needs cold and dry rest in winter but warm temperatures at summer. Most warm species normally grow in pots, but Dendrobium unicum suits better to be mounted on a slab.