I was fascinated by the buttonweeds, more because I was trying to decode the confusing identity of the plants in this group. Buttonweeds is found almost everywhere in Singapore, especially when the grass-trimming exercise was less frequent. Weedy plants are viewed to be of little or no commercial value are usually not very well studied, though some are considered as medicinal plant by some folks. Most of them have tiny white flowers which make them less attractive when compared to the other plants with more conspicuous and colourful flowers.
The name buttonweeds probably refer to their flowers clusters at leaf nodes that have the appearance of buttons. Though different species may look alike, they may not belong to the same genus as the buttonweed is simply a common name for such look-alike plants. Their flowers are usually very small, making their features difficult to be seen clearly with naked eyes. I had a tough time trying to differentiate the various species of buttonweeds. Though many plant pictures are available in the Internet, it is hard to determine whether they are naming them correctly or not since I have seen plenty of conflicting information. As for publications, few show pictures of the plants mentioned. Therefore, the botanical names I figured out on these buttonweeds in my website are based on my own deduction. Nevertheless, you can judge for yourself whether they are correct based on the pictures shown.visual comparison among them.
I first wrote this topic on buttonweeds in November 2012. Since then, I had not found any new buttonweeds till December 2015 when I came across the real Oldenlandia verticillata. Previously, I had mistakenly named Spermacoce pusilla as Oldenlandia verticillata. What I have done here is to show 2 photos of each buttonweeds that will hopefully allow a quick visual comparison among them.
Mitracarpus hirtus (White eye, small square weed, tropical girdlepod):
Spermacoce exilis (Pacific false buttonweed):
Spermacoce exilis looks very similar to Mitracarpus hirtus. The main difference, without going into the micro-features, is the veins on their leaves. The vein on the leaves of Mitracarpus hirtus is easily visible while that of Spermacoce exilis is hardly visible. Another distinction is that Spermacoce exilis tends to spread sideway while Mitracarpus hirtus tends to be more erected.
Spermacoce latifolia (Broad leaved buttonweed, Oval-leaf false buttonweed):
Spermacoce latifolia tends to have broader and rounded leaves when compare to the rest of the buttonweeds shown in this page. In fact, its flower cluster does not have the "button" look.
Spermacoce remota (Woodland false buttonweed, poaia):
Spermacoce remota tends to have leaves that are partially purplish in colour. The plant is usually unbranched.
Oldenlandia auricularia (Kerekah Batu):
Oldenlandia auricularia looks very similar to Spermacoce remota. The main difference is the flower cluster at the tip of the plant. The mature plant of Oldenlandia auricularia does not have any flower cluster at the tip while Spermacoce remota has one. Also, the leaves of Oldenlandia auricularia do not have the purple shade. Oldenlandia auricularia is the tallest among all the buttonweeds in this page.
Oldenlandia verticillata looks very similar to Oldenlandia auricularia. The visible difference is in the leaves. The leaves of Oldenlandia verticillata have no visible veins.
Spermacoce pusilla (Tiny False Buttonweed):
I had mistakenly named this plant as Hedyotis verticillata (synonym of Oldenlandia verticillata) for a number of years. It has the narrowest leaves among all buttonweeds shown in this page. It is also branched and usually found in water-logged wasteland or near the beaches.
(1) Tao C, Taylor CM. Spermacoce Linnaeus, Sp. Pl. 1: 102. 1753. Fl. China 2011; 19: 325-329. | Read article |
(2) Ward DB. Keys to the flora of Florida - 29, Spermacoce (Rubiaceae). Phytologia 2011; 93(3): 275-282. | Read article |
(3) Conserva LM, Ferreira JC Jr. Borreria and Spermacoce species (Rubiaceae): A review of their ethnomedicinal properties, chemical constituents, and biological activities. Pharmacogn Rev 2012; 6(11): 46-55. | Read article |
Last updated: 16 April 2016