5. Bidens subalternans DC. (S-Am.) – A rare and always ephemeral alien. First recorded in 1903 in Stembert and Verviers. Subsequently regularly seen in the Vesdre valley near Verviers as a wool alien, at least until 1970. Elsewhere occasionally recorded. More recent records are usually associated with grain importation, for instance on unloading quays in Turnhout (1968) and Izegem (1994, 1998) (Verloove & Vandenberghe 1995).
Bidens subalternans has been much confused with B. bipinnata in Belgium (Duvigneaud 1975b). The latter is much rarer and - until recently - was no longer recorded since 1915. Its leaf segments are much wider (see also Van Ooststroom & Reichgelt 1965 and Duvigneaud l.c. for further differences and line drawings).
Selected literature:
Bogosavljević S.S. & Zlatković B.K. (2015) Two alien species of Bidens (Compositae), new to the flora of Serbia. Phytologia Balcanica 21(2): 129-138. [available online at: http://www.bio.bas.bg/~phytolbalcan/PDF/21_2/PhB_21_2_04_Bogosavljevic_&... ]
Duvigneaud J. (1975b) Une espèce nouvelle pour la flore belge: Bidens subalternans. Bull. Soc. Roy. Bot. Belg. 108: 203-207.
Simon C. (1974) Bidens subalternans DC. in Europa. Bauhinia 5: 105-108.
Van Ooststroom S.J. & Reichgelt Th.J. (1965) Aanwinsten voor de Nederlandse adventief-flora. Gorteria 2: 137-143.
Verloove F. & Vandenberghe C. (1995) Nieuwe en interessante voederadventieven voor de Belgische en Noordfranse flora, hoofdzakelijk in 1994. Dumortiera 61-62: 23-45.