Hygrophila lacustris

Hygrophila lacustris is regarded as a synonym of Hygrophila costata, a swampweed that is also traded under this name.¹²³ The species occurs from the southern USA to southern South America and has spread invasively in eastern Australia.¹² The marsh plant grows up to 50 cm tall and bears narrowly elliptic, opposite leaves and small white flowers in the leaf axils; in Venezuela it was found in dense, semi-emersed stands in a floodplain.¹

Emersed cultivation of true H. costata is easy, often with flowers and fruits; in the aquarium, by contrast, it grows very slowly even under optimal conditions and is therefore only moderately suitable.¹ Soft water, a nutritious substrate and plenty of light are important.¹ The species is considered very variable, but whether plants traded as “lacustris” really belong to it is not certain. ^{H. costata” – Flowgrow forum (accessed 5 October 2026)">4}

1. Kasselmann, C. (2019): Aquarienpflanzen. 4th edition (German). - Ulmer Verlag, Stuttgart: p. 384.
2. Hygrophila costata – Plants of the World Online, Royal Botanic Gardens Kew (WCVP data as of 4 June 2026, accessed 5 October 2026)
3. Hygrophila – Aquarium and Pond Plants of the World, idtools.org (accessed 5 October 2026)
4. Thread “Hygrophila "angustifolia" von Tropica => H. costata” – Flowgrow forum (accessed 5 October 2026)