17 April 2016 | Buttonweeds | Family: Rubiaceae |
Buttonweed is a common name referring to a group of weedy herbaceous plants with flower clusters that looks like buttons. In Singapore, members in this group that belong to the Rubiaceae family. They are represented by 3 genera, namely Spermacoce, Oldenlandia and Mitracarpus. Not all members in these genera have flower clusters that look like buttons. There is another genus known as Hedyotis, but most in this genus are now being migrated to the genus Oldenlandia based on the information from the Plant List website.
I did a short write up on all the available buttonweed in Singapore back in 2012. Since then, I had not seen another new buttonweed until December last year. That was when I found Oldenlandia verticillata in a park. Before that, I had name another buttonweed (Spermacoce pusilla) with narrow leaves as Oldenlandia verticillata. When I checked the Flora of China website recently, it described Oldenlandia verticillata as “often decumbent” (meaning: lying along the ground or along a surface). It took me a while to feel confident on the identity of this plant because it looks very similar to another buttonweed, Oldenlandia auricularia. The distinction between the two is that Oldenlandia auricularia takes on an erected posture instead of having its belly along the ground.
Last week, another surprise related to buttonweed came along. I found another new buttonweed in the same area that I first saw Oldenlandia verticillata. This particular buttonweed has very narrow leaves and most of its stem goes along the ground as well. After some checks, I had identified it as Oldenlandia tenelliflora, thus adding another new plant for my website. Oldenlandia tenelliflora looks similar to Oldenlandia diffusa except that Oldenlandia diffusa is a much smaller plant and its flower has a stalk.
Both of the newly found herbaceous plants were not listed in the Singapore Flora checklist published in 2009. Below are pictures of the 3 plant for comparison. I had included pictures of Oldenlandia auricularia as reference.