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Short Notes on Nature Singapore

18 October 2020 | Snake-needle Grass | Oldenlandia diffusa |

The identity of the authentic Snake-needle Grass (Oldenlandia diffusa) remained a mystery to me until today. For years, since I first came across the plant in 2008 in Singapore, I was not able to figure out two slightly different plants that used the same name tag.

I believed the real guy was the one with a long fruit stalk. This feature was described in the Flora of China website as “peduncles elongating rapidly and markedly as fruit mature, to 20 mm”. Peduncle is flower stalk. I interpreted the description as “the flower stalk grow rapidly as the fruit mature reaching a length of up to 20 millimetres”. This description matched the plant that I first saw in 2008 which I had labelled as Candidate A. This plant was quite rare in Singapore.

Candidate A:

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The other guy with the same botanical name had fruits that was almost stalkless or sessile in botanical term. Its pictures in the Flora Fauna Web by by NPark were labelled as Hedyotis diffusa, a synonym of Oldenlandia diffusa. I finally got to see this plant physically at the same roof-top garden where I found the 2 new plants shared last week. It was used as ground cover. This sighting had prompted me to pen this short note on the 2 plants. To me,its appearance was quite similar to Oldenlandia tenelliflora except that it had single flower on each leaf axil while Oldenlandia tenelliflora had a few on each axil. This would be labelled as Candidate B.

Candidate B:

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Online information on this plant were mostly about its medicinal properties. With the exception of the Flora of China website, I could hardly find any other website that provide detailed description on the plant. Many pictures online labelled as Oldenlandia diffusa were actually Oldenlandia corymbosa which was a very common lookalike plant. In the iNaturalist website, there were 35 observations of Oldenlandia diffusa when I visited today. The pictures were a mixture of Candidate A, Candidate B and Oldenlandia corymbosa. The only observation in there from Singapore on 16 May 2019 was actually an Oldenlandia corymbosa.

In conclusion, Candidate A and Candidate B could not possibly be the same plant based on their appearance. Candidate A would be closer to the real stuff and Candidate B was likely to be something else.

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