Close-up views:

The seedling:

| Last updated: May 2025 |

Previously, I identified this naturalised plant as Acalypha alopecuroidea (Foxtail Copperleaf). In November 2021, I revised the name to the current designation, Acalypha arvensis, which is considered the correct botanical name for the plant found here according to a local publication in 2020 [1]. The article indicated that "Acalypha arvensis is often regarded as a synonym of A. aristata Kunth, but that name is synonymous with Acalypha alopecuroidea Jacq." (page 157). Additionally, the article noted that the plant was first collected in Singapore in 1955 (page 143). The misapplication of the name Acalypha alopecuroidea to this plant is corroborated by the 2022 Singapore flora checklist (page 316).

According to the Plants of the World Online website, Acalypha aristata is regarded as a synonym of Acalypha alopecuroidea. However, NParks' Flora & Fauna Web continues to utilize the name Acalypha aristata for this plant, with Acalypha arvensis listed as a synonym. This naming convention is also noted in a 2009 publication from Taiwan [2] and the updated checklist of Taiwan's naturalized flora published in 2022 [3].

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

As of 9 May 2025, the iNaturalist website recorded 20 observations of Acalypha arvensis in Singapore, with the first sighting documented in February 2021. Conversely, there were 15 observations of Acalypha alopecuroidea in Singapore, with the earliest and most recent observations reported in December 2017 and October 2024, respectively. It is suggested that all observations should be reclassified as Acalypha arvensis.

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 |

In 2021, I observed live specimens cultivated in my pot. The elongated, slender catkin-like structures contained densely packed male flowers. The shorter, broader greenish spike-like structures housed the female flowers, which eventually developed into fruits. Stipitate glands were found on the modified leaf structures (bracts) housing the female flowers. The stem of the plant did not exhibit stipitate glands.

| Plants of the World Online | iNaturalist | Global Biodiversity Information Facility (GBIF) |

[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 |