Local lore has it that the our common Dove Orchids flower ten days before rain. It is approximately correct on all points.
Just so we know what we’re talking about, here is the flower:
The flowers are quite small, about 5 cm across, but are abundant and have a lovely scent. Sometimes we walk into the garden, take a deep breath and realise the orchids are out before we see them. The flowers do only last for a couple of days, unfortunately, but they are very pretty for that time. Between flowerings, the plant is easily overlooked – a messy tangle of stems, roots and leaves, especially if it has been there for a while. The dull green leaves are 6 – 7 cm long and 2 – 2.5 cm wide.
Now, about all those partial truths:
- Dove orchids are not quite local. They are native to a broad area of southern Asia (from India, Malaysia, Indonesia and Vietnam to the Phillipines and China) but not, apparently, northern Australia. New Guinea and Christmas Island, yes; Australian mainland, no. But they are well established in gardens around Townsville, growing and propagating happily with no attention at all. If wouldn’t surprise me if they have gone feral along our tropical coast.
- ‘Dove orchid’ is the only common name used for them locally, and it is quite appropriate because the buds are shaped like little white birds; some people see a resemblance between the open blossom and a dove in flight, too. But ‘Dove Orchid’ is used for a quite different flower in Central America and some sources call ours the ‘Pigeon Orchid’. The scientific name is unambiguous, of course: Dendrobium crumenatum.
- How could a plant ‘know’ that it is going to rain? It can’t, of course. We thought for a long time that our orchids were responding to an increase in humidity but it turns out that flowering is triggered by a sudden drop in temperature (Orchids Wiki suggests ‘at least 5.5 C’ is needed) and all the flowers will open together nine days later, not ten, according to my sources. The temperature drop often precedes the onset of rain, so once again, a partial truth.
All of our dove orchids – four clumps of them in various trees and shrubs – flowered together last Friday. Let’s see if it pours rain tomorrow or Monday!
Friday 11 November: the results are …
Townsville got 3.8 mm of rain on Monday 7th, none at all in the week before that day and none in the following two days, according to the BoM stats.
The Monday was the tenth day after the orchids flowered, so it looks like local lore is vindicated. On the other hand, those rainfall figures are for the airport and we may not have had even that much of a shower – and 3.8 mm hardly qualifies as ‘rain’ anyway!
In the immortal words of the last paragraph of every scientific paper written in the last fifty years, ‘more research is required.’
