1. Verbesina alternifolia (L.) Britton (syn.: Actinomeris alternifolia (L.) DC.) (N-Am.) – A very rare, locally more or less naturalised escape from cultivation. First recorded in Oud-Heverlee alongside river Dijle in 1984 (three specimens but not confirmed afterwards). Known since at least 1986 from a woody verge of a former sandpit in Paal near Beringen (only two specimens). Also discovered in 2008 along river Sambre in Marpent (France, dép. Nord), close to the Belgian frontiers. Since then observed in scattered additional localities, for instance in Dessel, Deinze and Genk, usually in small number. Verbesina alternifolia always grows in more or less shady, rather damp, nitrophilous habitats.
The plants from Paal were initially ascribed to Verbesina helianthoides Michaux, a closely related species but apparently not cultivated as an ornamental in Europe (Brown 2000; see however Jäger & al. 2008). It usually has more ligular florets (8-13) but fewer heads (only 2-5(-10) versus 8-25(-50) in Verbesina alternifolia).
Verbesina alternifolia is sometimes cultivated by bee-keepers. At least the populations in northeastern France have been introduced on purpose (Geissert 1988).
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Selected literature:
Blink E. & Harle N. (2012) Verbesina alternifolia: een potentiële blijver. Natuurh. Maandb. 101(7): 131-133.
Brown N. (2000) Verbesina. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 650-651.
Geissert F. (1988) A propos de trois plantes adventices en Alsace. Bull. Assoc. Amis Jard. Bot. Col de Saverne 1988: 9-14.
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.
Oprea A. & Sirbu C. (2016) "Verbesina alternifolia" a new alien plant in Romania's flora. Acta horti botanici bucurestiensis 43: 85-96.
Schneider A. (1973) Découverte d'une deuxième localité de Verbesina alternifolia (L.) Britton, composée radiée. Monde Pl. 377: 5.
Weimer K. (1972) Verbesina alternifolia (L.) Britton – ein Neufund auf grenznahem, elsässischem Gebiet. Hess. Flor. Briefe 3: 44-46.