Adenostyles alliariae (Gouan) A. Kerner (Eur.) – An exceptional alien, recorded only once in 1971 on a stream-margin in woodland in Herbeumont (valley of river Semois) (Verloove 2006).
This is an enigmatic record: Adenostyles alliariae is apparently not cultivated as an ornamental since it rarely flowers in gardens (Jäger & al. 2008). According to these authors the usual garden plant is A. glabra (Mill.) DC. (syn.: A. alpina (L.) Bluff & Fingerh.). In Herbeumont it occurred in a natural environment that perfectly corresponds with its native habitat. The nearest native populations are in the Vosges in northeastern France. A native, disjunct population cannot be totally excluded. It is unknown if Adenostyles alliariae has persisted since 1971.
Selected literature:
Dillenberger M.S. & Kadereit J.W. (2012) Two new combinations in Adenostyles (Asteraceae, Senecioneae), a conspectus of the genus and key to its species and subspecies. Willdenowia 42: 57-61. [available online at: http://www.bioone.org/doi/pdf/10.3372/wi.42.42105]
Jäger E.J., Ebel F., Hanelt P. & Müller G. (eds.) (2008) Rothmaler Band 5. Exkursionsflora von Deutschland. Krautige Zier- und Nutzpflanzen. Springer Verlag, Berlin: 880 p.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/tabel_2.pdf]
Wagenitz G. (1983) Die Gattung Adenostyles Cass. (Compositae-Senecioneae). Phyton 23(1): 141-159.