Trifolium pannonicum Jacq. (EC. & SE.-Eur.) – An exceptional and ephemeral alien. Recorded once, in 2006, in Brussels, without further details. Perhaps a fodder alien (cf. Clement & Foster 1994).
Trifolium pannonicum had previously been claimed as an alien (see Lambinon & al. 2004) but collections prior to 2006 all originated from Luxemburg (Verloove & Lambinon 2008). This species is much reminiscent of native Trifolium ochroleucon but larger in all its parts. It may have been overlooked.
Selected literature:
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Lambinon J., Delvosalle L., Duvigneaud J. (avec coll. Geerinck D., Lebeau J., Schumacker R. & Vannerom H.) (2004) Nouvelle Flore de la Belgique, du Grand-Duché de Luxembourg, du Nord de la France et des Régions voisines (Ptéridophytes et Spermatophytes). Cinquième édition. Jardin botanique national de Belgique, Meise: CXXX + 1167 p.
Verloove F. & Lambinon J. (2008) Neophytes in Belgium: corrections and adjustments. Syst. Geogr. Pl. 78: 63-79. [available online at: http://www.jstor.org/discover/10.2307/20649750?uid=3737592&uid=2129&uid=2&uid=70&uid=4&sid=21102533631713]