1. Rorippa austriaca (Crantz) Besser (C- and E-Eur., W and C-As.) – A very rare but slightly increasing, locally naturalised alien. First recorded near a grain mill in Wilsele between 1893 and 1895. Observed as a wool alien in the Vesdre valley between 1912 and 1952. At present best known from Brussels (see Saintenoy-Simon & al. 1995 and Saintenoy-Simon 1997 for an overview of its history in Brussels) and well-naturalised since at least the 1950’s (Elsene, Etterbeek, Ganshoren,…). In the past decades also recorded in well-established, often large populations in Brustem, Handzame (now destroyed), Hasselt (canal bank), Mesen, Passendale, Scherpenheuvel (large population), Wilrijk (road verge since at least 2000),…. The origin of most recent populations – nearly all in road verges – remains obscure. Rorippa austriaca was formerly introduced with grain and wool but an obvious vector of introduction is lacking for recent records. Its rhizomes are probably transported with ground. Rorippa austriaca usually grows in road verges or canal banks, often in slightly disturbed conditions. Elsewhere in Europe it is often considered as an invasive alien in more natural habitats (mainly riverbanks). Rorippa austriaca is a strongly rhizomatous perennial and easily produces dense, nearly monospecific stands. In Belgium, so far, it is confined to non-natural habitats.
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Selected literature:
Keil P. (1999) Ökologie der gewässerbegleitenden Agriophyten Angelica archangelica ssp. litoralis, Bidens frondosa und Rorippa austriaca im Ruhrgebiet. Diss. Bot.321: 186 p.
Saintenoy-Simon J. (1997) Le Quartier Nord, à Bruxelles, une pépinière d’espèces rares. Adoxa17: 22-24.
Saintenoy-Simon J., Godefroid S. &Verhelpen B. (1995) Groupe Flore Bruxelloise. Notes floristiques relatives à la Région de Bruxelles-Capitale (1991-1993). Adoxa6-7: 27-37.
Sauerwein B. (1987) Rorippaaustriaca (CR.) Bess. in Ruderalgesellschaften auf der Henschelhalde in Kassel. Hess. Flor. Briefe36(4): 55-60.
Vanhecke L. (2006) Rorippa austriaca. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de flora van Vlaanderen en het Brussels gewest. InstituutvoorNatuur- en Bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 754.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.