Hydrocotyle sp. "Japan"

Hydrocotyle sp. “Japan” is a trade name for a pennywort that is listed here as a synonym of Hydrocotyle cf. tripartita and is also sold as H. tripartita; it reached Europe in 2008 from Thailand and in 2010 from Japan.¹² Its origin is mostly placed in Australia, although South-East Asia is sometimes given.¹²⁵ Flowers and fruits match H. tripartita, native to Australia and New Zealand; the fact that the aquarium plant is hairless and has less deeply divided leaves probably falls within the species' range of variation.³⁵

Its leaves, deeply divided into three to five lobes, are somewhat reminiscent of clover.¹ With plenty of light, CO₂ and nutrients it quickly grows into dense cushions approx. 5–10 cm tall; for this, small clumps are planted in the foreground and the stand is thinned out regularly.¹²⁴⁵ It can also be used attached to roots or lava.⁵

1. Hydrocotyle cf. tripartita – Flowgrow aquatic plant database (accessed 5 October 2026)
2. Hydrocotyle tripartita – Tropica Aquarium Plants (accessed 5 October 2026)
3. Hydrocotyle tripartita – Plants of the World Online, Royal Botanic Gardens Kew (WCVP data as of 4 June 2026, accessed 5 October 2026)
4. Hydrocotyle tripartita – Aquasabi (accessed 5 October 2026)
5. Kasselmann, C. (2019): Aquarienpflanzen. 4th edition (German). - Ulmer Verlag, Stuttgart: p. 376.