Thursday, October 8, 2009

Black Orchid

Cymbidium canaliculatum
Bushwalkers always find something to delight them. This magnificent black orchid was flowering its heart out in a dead ironbark tree last week. No doubt the tree had a big long hollow, which accommodated the plant’s enormous root system. More roots, had clearly formed since the tree’s death, as they were between the timber and the bark. The bark was peeling off, so the orchid will have to retrench a little when it goes.
I hope the orchid goes on in good health for many years though. There are good reasons for leaving hollow dead trees where they stand. The feather glider, which popped out while we were admiring the orchid, is another.
Ironbark timber is so strong that a dead one can stand for hundred years or more, still doing its bit for the ecology.
This lovely plant is Australia’s most drought-hardy orchid, and is common in the bush in our district. It‘s a plant of the inland, unusual in preferring to grow well away from the rainforests and vine scrubs which are the preferred habitat of most orchids.
It usually grows in hollow eucalypt trees, where the rhizomes ramble through the dark tunnels and rotten heartwood, and pop out leaves wherever opportunities arise. “Plants” which seem far apart - like the three in a Eucalyptus tereticornis not far from this specimen - may well all be part of the same plant. A large old specimen can have roots 10 metres long.
The name “canaliculatum” refers to the channel-shaped leaves, which direct rainwater and dew towards centre of the plant. This is part of the secret of the plant's drought hardiness. The other part is the huge root system, protected from dehydration in its well-insulated, deep tunnels. Orchids are usually regarded as acid-loving plants, so the discovery that the ends of the roots of big, old plants like this are actually in very alkaline conditions (pH 9!) is somewhat startling.
Black orchids often grow in exposed places well away from the shelter of any trees, and have even been known to establish themselves in fence posts. They are said to prefer a north-east aspect, but are certainly seen thriving in other positions.
Orchid enthusiasts from our coastal cities regard this as a rather difficult orchid to grow. It is uncomfortable in the humidity. We have an advantage over our coastal friends there, but it is very rare indeed to see a cultivated specimen as magnificent as this. It’s difficult to give it the conditions it really prefers!
These orchids - like many other of our native orchids - are easily killed by root disturbance, so trying to take an established plant like this home is most likely to kill it. Orchid “collecting” is usually just another name for vandalism - and of course, taking plants from the wild is illegal, unethical, and much resented by bushwalkers and other genuine lovers of Australia’s wild plants.

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