Gaudinia fragilis (L.) Beauv. (syn.: Avena fragilis L.) (S-Eur., W-As., N-Afr., Macaronesia) – A very rare and casual alien of obscure origin. It was apparently last recorded in 1953 on a dump in Mechelen and was seen before in various places (Antwerpen, Arlon, Ath, Drogenbos, Landelies, Lobbes, Montigny-le-Tilleul, Ruisbroek) (Druet & Duvigneaud 1951). Gaudinia fragilis was found in man-made to more or less (semi-) natural habitats, e.g. sandpits, railway tracks, wastelands or wood-margins. It was perhaps sometimes temporarily persisting in some of these places.
Gaudinia fragilis is native in parts of northern France, relatively close to the Belgian borders (see Tela-Botanica at: http://www.tela-botanica.org/bdtfx-nn-29424-synthese). In 2014 it was re-discovered in Belgium in a meadow in Houyet (nature reserve Pré de Happe Tortia) in the Famenne, close to the French borders. At present (2017) a small population with ca. 100 plants seems to persist well. The origin of this population is unknown. It is tempting to think of a natural range expansion. However, the reserve was created (few years before, in 2007) and the species may have been introduced accidentally on this occasion. According to Tison & de Foucault (2014) populations of Gaudinia fragilis in northern France are probably naturalized, not native. The species was said to be in expansion, especially in northeastern France. See also Levy (2014). Similar uncertainties about its status exist for instance in the British Isles (e.g. Leach & Pearman 1997, Leach & Pearman 2003). Gaudinia fragilis is an annual species and often rather ephemeral. It is uncertain whether or not it will be able to naturalize and spread from this single Belgian locality.
Selected literature:
Booth E.M. (1967) Gaudinia fragilis (L.) Beauv. in Co. Clare. Irish Naturalists' J. 15: 331.
Druet J. & Duvigneaud J. (1951) Note sur quelques phanérogames adventices. Lejeunia 15: 59-62.
Farragher M.A. (1968) Gaudinia fragilis (L.) Beauv. - another station. Irish Naturalists' J. 16: 53.
Green D. (1990) Gaudinia fragilis in N. Wilts. B.S.B.I. News 54: 22. [available online at: http://archive.bsbi.org.uk/BSBINews54.pdf]
Leach S.J. & Pearman D. (1997) Gaudinia fragilis - is it native? B.S.B.I. News 77: 35-36. [available online at: http://archive.bsbi.org.uk/BSBINews77.pdf]
Leach S.J. & Pearman D.A. (2003) An assessment of the status of Gaudinia fragilis (L.) P. Beauv. (Poaceae) in the British Isles. Watsonia 24(4): 469-487. [available online at: http://archive.bsbi.org.uk/Wats24p469.pdf]
Levy V. (2014) Découvertes et curiosités. La Gaudinie fragile, un retour remarqué dans la flore picarde. Le Jouet du Vent 27: 3. [available online at : http://www.cbnbl.org/IMG/pdf/bd_jouet_du_vent_pour_le_net.pdf]
McClintock D. (1967) Gaudinia fragilis (L.) Beauv. Bot. Soc. Brit. Isles Proc. 6: 391. [available online at: https://www.biodiversitylibrary.org/item/188473#page/485/mode/1up]
McClintock D. (1973) Gaudinia fragilis (L.) Beauv. Watsonia 9: 143-146. [available online at: http://archive.bsbi.org.uk/Wats9p137.pdf]
O'Sullivan A.M. (1967) Gaudinia fragilis (L.) P. Beauv., in Limerick grassland. Irish Naturalists' J. 15: 343-345.
Pearman D. (1989) Gaudinia fragilis in Dorset. B.S.B.I. News 53: 20-21. [available online at: http://archive.bsbi.org.uk/BSBINews53.pdf]
Scannell M.J.P. (1964) Gaudinia fragilis (L.) Beauv. in Ireland. Irish Naturalists' J. 14: 215-216.
Schneider T. & Schneider C. (1998) Der Ährenhafer, Gaudinia fragilis (L.) P.B., in der Flora der Nied und ihrer Grenzregionen (südöstliches Lothringen): Verbreitung, Standorte und Vergesellschaftung. Delattinia 24: 179-194. [available online at: https://www.delattinia.de/sites/alienplantsbelgium.bedefault/files/pdf/a...
Tison J.-M. & de Foucault B. (coord.) 2014) Flora Gallica. Flore de France. Editions Biotope, Mèze : xx + 1196 p.
Wacker F. (1972) Sesshaftwerden eines fremden Grases. Ährenhaber (Gaudinia fragilis (L.) P.B.) auf Naturwiesen am Unterlauf der Schutter. Mitt. Bad. Landesver. Naturk. Naturschutz 10(3): 543-546. [available online at: http://www.zobodat.at/pdf/Mitt-Bad-Landesver-Natkde-Natschutz-Freiburg_N...