First report of Hydrocharis laevigata in France
Hydrocharis laevigata (Hydrocharitaceae, synonym Limnobium laevigatum) is a floating aquatic plant native to South and Central America. It can invade freshwater habitats including shallow ponds, lakes, dams, reservoirs, and slow-moving rivers. It has the potential to outcompete native aquatic plant species and change the chemical composition of the water body. In the EPPO region, it has been reported as transient in Belgium, Hungary, Poland and Spain (EPPO RS 2021/114, RS 2021/202). In France, H. laevigata was first observed in 2022 in a reservoir on the river Vilaine (Ille-et-Vilaine departement, Bretagne region). In 2023, it was found at a further four sites on the banks of the Garonne and Lot rivers (Lot-et-Garonne and Gironde departements, Nouvelle Aquitaine region). Floating mats of the plant have been observed. Along riverbanks, H. laevigata has been identified as early as April in the growing season. Up to 100 individuals were observed on the river Lot.
A risk assessment has been produced for Hydrocharis laevigata for the European Union and the species will be considered for listing under the Invasive Alien Species Regulation (Regulation (EU) 1143/2014).
Sources
Dutarte A (2026) Limnobium laevigatum s’installerait-il dans l’hexagone ? [Is Limnobium laevigatum establishing itself in France?]. Invasive Alien Species Resource Centre. Available at: https://especes-exotiques-envahissantes.fr/limnobium-laevigatum-installer-hexagone/
Kudrnovsky H, Williams M (2024) Draft risk assessment for Hydrocharis laevigata. Available at https://circabc.europa.eu/ui/group/98665af0-7dfa-448c-8bf4-e1e086b50d2c/library/25d41f8f-ea24-48bc-9c6e-2955ab911815/details