1. Petasites albus (L.) Gaertn. (C-Eur., W-As.) – A very rare, temporarily persisting or locally naturalised alien (most of the time probably a mere relic of cultivation in or near estates, parcs, etc.). First collected, without further details, in 1862. Seen in Clairefontaine in 1968, along with Asarum europaeum and Eranthis hyemalis (Parent 1968; erroneously as Petasites fragrans in d’Ansembourg & al. 1967), but not confirmed lately. Since 2010 a large population (at least 200 plants) is known from a track in woodland in Mont (Houffalize), again with Asarum europaeum. Other recent records, for instance from La Hulpe (border of Argentine riverlet) and Haccourt, require confirmation.
Selected literature:
D’Ansembourg V., De Zuttere P., Louette A., Matagne G. & Parent G.H. (1967) Quelques plantes vasculaires intéressantes de l’Ardenne méridionale et du district jurassique. Lejeunia N.S. 44: 47 p.
Berlin A., Hoffmann H. & Nuchel G. (1976) Petasites albus (L.) Gaertner (Asteraceae) neu im Mittelrheingebiet. Decheniana 129: 9-10.
Braun-Blanquet J. & Sutter R. (1977) Die Petasites albus-Aruncus dioicus-reiche Hochstaudenvegetation Graubündens (Arunco-Petasition all. nov.). Mitteilungen der floristisch-soziologischen Arbeitsgemeinschaft 19/20: 313-317.
Clement E.J. (1981) Aliens and adventives. Adventive news 18. Petasites albus. BSBI News 26: 19.
Fellenberg W. (1980) Zur Verbreitungsgrenze der Weissen Pestwurz (Petasites albus) in Westfalen. Dortmunder Beitr. Landeskde. 14: 103-109.
Hirtz O., Riepe D. & Schumacher W. (1984) Neufund von Petasites albus (L.) Gaertn. (Asteraceae) bei Hellenthal/Westeifel. Decheniana 137: 61.
Parent G.H. (1968) Notice sur le vallon de Clairefontaine (province de Luxembourg). Nat. Mosana 21(2): 73-80.