Close-up views:

The seedling:

| Last updated: February 2023 |

I had previously named this naturalised plant as Acalypha alopecuroidea (Foxtail Copperleaf). In November 2021, I changed it to the current name, Acalypha arvensis, which I believe should be the correct botanical name of the plant found here based on a local publication in 2020 [1]. The article stated that "Acalypha arvensis is often considered to be a synonym of A. aristata Kunth, but that name is a synonym of Acalypha alopecuroidea Jacq." (page 157). The same article also mentioned that the plant was first collected in Singapore in 1955 (page 143).

In NParks' Flora & Fauna Web, the name Acalypha aristata was still used as of this update and it listed Acalypha arvensis as a synonym. The same treatment of the names was also reported in a 2009 publication from Taiwan [2] and the updated Checklist of the Naturalized Flora published in 2022 [3]. However, according to the World Flora Online and Plants of the World Online websites, Acalypha aristata is a synonym of Acalypha alopecuroidea. The Flora of North America website stated that "Some recent literature misapplies A. aristata Kunth to this species, but that name is a synonym of A. alopecuroidea".

According to the Flora of North America website, the stem of Acalypha alopecuroidea is described as "stipitate-glandular" which means having hairs with a rounded gland at the distal end, also known as glandular trichomes. Same descriptions that differentiate the 2 similar-looking plants can also be found in publications [4, 5].

In the iNaturalist website viewed on 18 February 2023, there were 11 sightings of Acalypha arvensis in Singapore with the first sighting reported in February 2021. On the other hand, there were also 11 sightings for Acalypha alopecuroidea in Singapore from the same website with the first sighting reported in December 2017. All of them might be Acalypha arvensis instead.

Reference:

[1] van Welzen PC, Middleton DJ, Lindsay S. Flora of Singapore precursors, 21: New records of Euphorbiaceae for Singapore. Gardens' Bulletin Singapore 2020;72(2):143-158. | Read article |

[2] Chen SH, Su JY, Wu MJ. Notes on Two Newly Naturalized Plants in Taiwan: Evolvulus nummularius (L.) L. (Convolvulaceae) and Acalypha aristata Kunth (Euphorbiaceae). Taiwania 2009;54(3):273-278. | Read article |

[3] Chang-Yang CH, Su MH, Chiang PH, Hsieh CF. Updating the checklist of the naturalized flora in Taiwan. Taiwania 2022;67(1):1-8. | Read article |

[4] Sanz JM, Rodríguez PM. Synopsis of Acalypha (Euphorbiaceae) of continental Ecuador. PhytoKeys 2012;(17):1-17. | Read article |

[5] Cardiel JM, de Sousa AAC, Cordeiro I, Caruzo MBR, da Silva OLM, Muñoz-Rodríguez P, López A, & Montero-Muñoz I. Updated synopsis of Acalypha (Euphorbiaceae, Acalyphoideae) from Brazil. Plant Systematics Evolution 2022;308(4):24. | Read article |

I had the opportunities to observe live specimens grown in my pot in 2021. The elongated slender catkin-like structure contained tightly packed male flowers. The shorter but broader greenish spike-like structure housed the female flowers which will eventually turn into the fruits. Stipitate glands were found on the modified leaf structure (bracts) that housed the female flowers. The plant did not have stipitate gland on the stem.

| Flora of North America | Plants of the World Online | Global Biodiversity Information Facility (GBIF) | Leon Levy Native Plant Preserve | Atlas of Florida Plants | Smithsonian Tropical Research Institute | Tresaure Coast Natives |

[2022] Ble-González EA, Gómez-Rivera A, Zamilpa A, López-Rodríguez R, Lobato-García CE, Álvarez-Fitz P, Gutierrez-Roman AS, Perez-García MD, Bugarin A, González-Cortazar M. Ellagitannin, phenols, and flavonoids as antibacterials from Acalypha arvensis (Euphorbiaceae). Plants (Basel) 2022;11(3):300. | Read article |