Fig. 2: Flower of Richardia scabra (Rough Mexican Clover)

In the final week of November 2024, I observed a relatively large population of Richardia scabra (Rough Mexican Clover) along the roadside adjacent to a construction site near my residence. As this wild herbaceous plant is not commonly encountered, I decided to collect a specimen for further examination. The specimen was subsequently transplanted into a pot and placed in my balcony area. It has since adapted well to the potted environment, continuously producing small white flowers with button-like inflorescences.

My initial observation of this buttonweed in Singapore occurred in May 2007 along a drainage area in Sembawang (Figure 1). It was not officially recorded in Singapore until a publication in 2021 [1]. Although I encountered this plant sporadically over the years, I lacked opportunities to capture additional photographs during those times. This species appears to be relatively rare compared to other buttonweeds such as Mitracarpus hirtus (Tropical Girdlepod) and Spermacoce exilis (Pacific False Buttonweed), which are more commonly found in the park adjacent to my residence. Compared to these two similar species, Richardia scabra is characterized by its larger flowers (Figure 2) and low, spreading growth habit.

Fig. 1: Pictures of Richardia scabra (Rough Mexican Clover) taken in 2007

While updating photos of Richardia scabra, I reviewed the genus Spermacoce in Singapore according to the 2022 Singapore flora checklist. My website features images of 6 Spermacoce species. To gauge their local prevalence, I tabulated observations from Singapore on the iNaturalist website as of 12 January (Table 1).

The flora checklist documented eight Spermacoce species, including two classified as extinct in Singapore: Spermacoce ocymoides and Spermacoce parviceps. Notably, Spermacoce parviceps was recognized as a new national record for Singapore in 2018, based on a herbarium specimen last collected in 1955 [1]. There was an observation of this species reported in 2024 on the iNaturalist website. Regarding Spermacoce ocymoides, several images are displayed on NParks’ Flora & Fauna Web (viewed on 8 January), but they resemble Spermacoce remota (Woodland False Buttonweed) more closely. Nevertheless, some photographs of Spermacoce ocymoides can be found on the Urban Forest website.

Although my website does not feature images of Spermacoce hispida (Shaggy Buttonweed), it does contain images of a similar-looking species, Spermacoce articularis (Jointed Buttonweed), which I encountered overseas in 2008. Spermacoce articularis is not included in the flora checklist. According to comments on the iNaturalist website, Spermacoce hispida shares several characteristics with Spermacoce articularis. As of now, there have been 15 documented observations of Spermacoce articularis from Singapore on the iNaturalist website.

Following the review, I have updated the images previously labelled as Spermacoce pusilla to Spermacoce verticillata (Shrubby False Buttonweed). The remaining four species on my website are included in the flora checklist.

References:

[1] Chen LMJ, Ong KH, Lua HK, Yeo RSW, Chua KS, Tan BH, Choo LM, Koh SL, Ho BC. Additions to the Flora of Singapore: New and overlooked records of casual and naturalised plant species (5). Nature In Singapore 2021;14:e2021090. | Read article |