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Vol. X No.14 - August 1 - August 31, 2011


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How does your garden grow?  By Eric Danell, Dokmai Garden

 


An upside down orchid

The upside down orchid; the greater yellowspike
(Polystachya concreta, Orchidaceae

In many cases orchids have fairly restricted ranges. Some are endemic to Thailand (such as Chiloschista viridiflava), some are only found here in the north and in adjacent countries with similar monsoon forests (such as Seidenfadenia mitrata), some are only found in Southeast Asia (such as Vanda denisoniana).

On the other hand, there are orchids such as Calypso bulbosa which are circumboreal, i.e. you can find it Scandinavia (although rarely now due to habitat destruction), Japan and North America. In a previous blog we discussed why epiphytic orchids never made it to Europe, and in another blog I mentioned that some ornamental orchids have been introduced and naturalized elsewhere.

Here I hold a detached flower upside down, and then it looks like a ‘normal’ orchid with the column at top.

On the 16th of August I photographed the blossom of a native Thai orchid which also occurs in Africa and South America: The greater yellowspike (Polystachya concreta, Orchidaceae). The genus Polystachya (meaning ‘many spikelets’) with some 150 species is largely African, and this species is hitherto the sole representative known in Asia. Being one of the most widespread orchid species in the world, it is not endangered like so many other Thai orchids.

Although the literature claims it has no horticultural value, I must say I was enchanted by its decorative, erect, yellow spike with its peculiar buds, and when the flower unfolded they looked like little girls with long blond hair. The specimen of the Orchid Ark grows on a branch together with Vanda flabellata. This species is known to grow in dry environments on dipterocarp branch ends. Since I do not know much of the background of this branch with its two orchids, other than it was donated to the Orchid Ark, I think we dare to restore it to a Dokmai Garden Dipterocarpus tuberculatus tree. If anyone would like to study this little wonder, now is the time!

The flower is strange! From a picture you do not grasp what you are looking at. I had to use a nail scissor and carefully detach a stiff (‘concreta’) flower to study it with a 20x dissecting microscope. It turns out, this is an upside down flower! Most orchids are resupinate, meaning they have the lip below the column. In this case, the flower is not resupinate, i.e. the lip is on top. What you see on this photograph are the sepals unfolded like a blond girl’s hair, exposing what is normally the underside of the lip. (Unfortunately I have no camera attached to that microscope).

Why would an orchid flower grow upside down? We can only hypothesize. Maybe the pollinia were better protected on the lower side of the pollinating insect rather than being attached to the eyes, head or thorax which is more common? Perhaps the pollinating insect kicks around a lot, and so firmly trample the pollinia into the stigma, the female part? Apparently this flower trait became superior in the orchid’s reproduction so that upside down flowers resulted in more seedlings than in plants with normal flowers, and this original mutation has so far resulted in a genus of 150 species. Why are there not more of them in Asia? We do not know when the mutation occurred. Nothing in nature in fixed, the environment is continuously changing and mutations occur all the time, and so Polystachya concreta might be the first scout of its genus to the Asian continent, not yet found in New Guinea or Australia. www.dokmaigarden.co.th. [email protected]
 



Sick cicada?

The mosquito finally found a good spot and dived in. The giant cicada (Megapomponia sp.) is among the largest cicadas in the world (head-body 7 cm, head-wing tips 10 cm).

I thought mosquitoes were adapted to suck blood from larger animals (vertebrates). I was wrong!

One early morning at daybreak I staggered out with my son. Passing the bathroom I saw a huge cicada and a little insect buzzing around him. My son did his morning toilet and went off to granny, and I took a closer look at the cicada. Really – a mosquito was tormenting him. I ran off to get my camera, wondering if there are mosquitoes specialized in insects? The mosquito was still there and so I got some time to take photographs. It seemed the mosquito was probing the cicada, and I guessed me sitting 30 cm away with a larger body radiating sweat, CO2 and heat would make the mosquito change target – but no! That seemed like an adaptation to insects, as the cicada was probably not hotter than the surrounding air. It also seemed that the mosquito dived in between the chitin plates, an obvious place. Insects do not have blood like us, but they have haemolymph, a liquid surrounding the internal organs. This haemolymph is as nutrient rich as any blood.

Does it have any significance to know that cicadas can be affected by mosquitoes? During the Second World War more Australian soldiers died from tsutsugamushi fever than from Japanese bullets. Thanks to the Australian pediatrician Ron Southcott (a mentor of mine when I was a teenager) who made his service in New Guinea, science learnt that mites spread the disease from rodents to man. This knowledge is as important as any military intelligence to defeat your enemy.

The observation of mosquitoes on cicadas makes me think: plant virus – plant – cicada – mosquito – are there other vectors and hosts in the chain? Viruses may jump from duck to pig to man, and rhabdo viruses spread between most mammals. Viruses highjack cells and make them produce viruses instead of cell proteins. They may rearrange the host’s DNA, and may even bring some DNA from one host and incorporate it into another species. This phenomenon of natural GMO (genetically modified organisms) may have occurred since the first bacteria, and may have contributed to leaps in evolution. Some human diseases originate in rodents, cats and snails, and maybe there are reservoirs in seemingly harmless insects too?

A real scientist would have collected both cicada and mosquito and spent time investigating it. I am just a gardener, but if any entomologist is curious feel free to visit Dokmai Garden and make some studies.

The mosquito is unfortunately out of focus but is seen to the left on the head. The bright rubies are two of the three ocelli (eyespots). www.dokmaigarden.co.th. [email protected]
 


Curry Leaf

Curry’ is a word referring to hot spicy mixes. There are endless variations with different ingredients. Curry leaf (Murraya koenigii, Rutaceae) is a well known ingredient in many Indian curries, but what about the western curry, what the westerners would refer to as ‘curry smell’? It is derived from the seeds of a plant called fenugreek (Trigonella foenum-graecum, Fabaceae). The characteristic ‘curry fragrance’ of fenugreek can be found in other plants and even mushrooms, and can be of diagnostic help.

One plant commonly sold in Thailand is Sauropus thorelii (Phyllanthaceae/Euphorbiaceae). We can call it ‘curry flower’ in English, as the most conspicuous trait of the red flowers is the fragrance of fenugreek or ‘curry’. The leaves have no such fragrance, and the leaves are indeed quite pleasant to eat raw. The plant is only known from Thailand and Laos

The Curry leaf, Murraya koenigii, Rutaceae.

The underside of a curry flower branch. Each leaf has two sharp thorn-like stipules. Note the zigzag growth of the glabrous stem. You will also feel two ridges with your fingers. The inflorescence’s fragrance of ‘western curry’ is conspicuous, but you may encounter other Sauropus with a similar fragrance. According to Flora of Thailand there are 27 species of Sauropus in Thailand. Traditionally Sauropus has been grouped within the rubber tree family Euphorbiaceae, although Sauropus lacks the typical white latex. Lately, plants with Euphorbia-like blossom but which lack the latex have been grouped in the Phyllanthaceae family. I think that makes sense.

Welcome to visit Dokmai Garden in Chiang Mai where you can taste both curry leaf and curry flower. With this new species we hit 1055 plant species in our collection. To study such a vast number you need many days. You may therefore want to consider investing in a VIP card with unlimited access for a year, or you take a tropical gardening school class. You pay to obtain knowledge, and we use the money to run Dokmai Garden and the Orchid Ark. Cheaper than golf! www.dokmaigarden.co.th. [email protected]
 


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