New records of Hydrocotyle ranunculoides in France
Hydrocotyle ranunculoides (Apiaceae – EPPO A1 List) is now reported from several locations in France. The species was first found in 1987 in the Essonne department in one site, and since then, it has been recorded in 7 new sites belonging to the same water system (G. Arnal, pers. comm., 2009). It also occurs in several rivers in Picardie and in the Nord (including Villeneuve D’ascq and Haverskerque) and Eure departments. In 1999, the plant was reported in the surroundings of Paris and in Corsica, and in 2007, the plant was observed in the Loire-Atlantique departement.
In Loire-Atlantique, the species was found in January 2007 in La Turballe covering 40 m² of a deep ditch adjacent to salt marshes, together with Eichhornia crassipes (Pontederiaceae – EPPO A1 List) and Pistia stratiotes (Araceae – EPPO Alert List). The presence of these 3 species probably results from the cleaning of an ornamental pond. The latter two species were easily removed, but the control of H. ranunculoides was more difficult. Manual removal of H. ranunculoides was organized in February 2007 with 7 volunteers. The species was monitored several times at this location in order to detect and remove plant fragments hidden in the mud, which could lead to new infestations. In August 2007, the species was observed again on the same site and was removed. This site is now the object of constant monitoring. The authorities and relevant organizations have been informed of the occurrence of this invasive plant, and several articles have been written.
In Loire-Atlantique, the species has also been observed in Saint-Brévin les Pins, covering a lake. Although the species had been mechanically removed from this location, it has subsequently reinvaded the lake.
In 2008, the species was also found in the Authion Valley, East of Angers in the Maine-et-Loire department, and a monitoring programme will be organized in 2009.
Agence de l'eau Artois-Picardie (2005) Les espèces végétales invasives des milieux aquatiques et humides du bassin Artois-Picardie. 40 pp. http://www.eau-artois-picardie.fr/IMG/pdf/Flore-4.pdf
Buchet J (2007) Le jouet du vent : Lettre d’information semestrielle du Conservatoire botanique national de Bailleul, numéro 18, p 4. http://220.127.116.11/digitale-rft/site/Telechargements/JouetDuVent_Pdf/jouet_18.pdf
Lachaud A (2009) Une nouvelle invasive pour le Massif armoricain : Hydrocotyle ranunculoides L. f. Conservatoire Botanique National de Brest, ERICA 22: 3-10
Reduron JP (2007) Ombellifères de France. Bulletin de la SBCO, nouvelle série - n° spécial 28, tome X, 1542-1543.
Personal communication with G. Arnal, Conservatoire Botanique du Bassin Parisien (FR), 2009.