Submitted by wellsy on Sun, 17/02/2008 - 09:20
Dendrobium Swartz 1799
Type Species: Dendrobium moniliforme (L.) Sw. 1799
Dendrobium adae (photo - above)
Dendrobium thysiflorum (photo - above)
Dendrobuim unicum (photo - above)
Dendrobium is a large genus of tropical orchids that consists of about 1200 species. The genus occurs in a diverse range of habitats throughout Korea and Japan, China, West to India and Sri Lanka, down through Peninsular Malaysia, Indonesia, Borneo, the Philippines, Guam, New Guinea (where 500 species are known) to Australia, New Zealand and as far east as Tahiti in the Pacific Ocean. Plants produce pseudobulbs along rhizomes (sometimes they are well spaced on the rhizome) which are generally quite long but can also be short. Leaves are usually alternate along the length of the psuedobulb but can be shed after one season in deciduous species. Most species are epiphytic while a few are lithphytes, terrestrials or semi-terrestrials.
Although they are generally found in quite bright and exposed situations (some Australian species tolerate full sun on exposed granite rock shelves) most plants are found in the tops of trees on outer branches and in crevices in limbs which offer some protection. A few species prefer the cooler moister regions of the forest in and around creeks etc. Most, if not all plants will begin a period of dormancy at the beginning of drier or cooler months. They commence growth from dormant eyes or buds around the base of the pseudobulbs. These will grow rapidly in times of good rainfall and warm conditions but will slow if conditions become adverse.
When it is time to repot Dendrobiums the old canes (psuedobulbs) should be left intact on the plant until they are very obviously brown and shrivelled to almost nothing. However, if the psuedobulbs do go mushy and obviously dead before then definitely remove them by severing near the base with clean secateurs. The old psuedobulbs act as a storage mechanism for the plant to use up on making the new growths so to remove them you remove the plants stored food supply. Most growers like to keep dendrobiums potted small but obviously if the plant is growing well and you know it is going to be a large plant (or you intend to grow it to specimen size) then at some stage you need to put it in a larger pot.
Most often Dendrobiums are grown in a very coarse media with large chunks of treated pine bark, charcoal, gravel and other similar substrate. A general rule is to size the chunks according to the size of the plant. Seedlings and smaller growers require smaller chunks while large species or specimens benefit from larger chunks to allow greater air movement in the media. Repotting is only required if the media becomes stale or breaks down (becomes muddy and/or smells sour). It is best not to repot unless the mix is in this state or a larger pot is required. When a larger pot is required and the mix is in good condition, the old pot can simply be removed and the remaining mass can be fitted into a new larger pot and new media pushed in to fill the gaps. It may be necessary to add a stake at this stage to support the weight of the plant while the plant grows in to the new media.