1. Cosmos bipinnatus Cav. (syn.: Bidens formosa Schinz) (U.S.A., Mexico) – A common ornamental and fairly often escaping but very poorly documented in Belgian herbaria. Apparently first collected on dumps in Lambermont in 1954 and Saint Servais in 1955. Subsequently seen in rather few, widely scattered places but always ephemeral. Most records are associated with garden waste but Cosmos bipinnatus is sometimes found among birdseed aliens as well (Verloove & Vandenberghe 1996; see also Hanson & Mason 1985).
Plants in cultivation are rather variable and some races hardly look like the wild type (Kiger 2006). Ligules are usually rose-pink or lilac (Johnstone 2000) but white-flowered plants are also frequently encountered in Belgium.
References
Hanson C.G. & Mason J.L. (1985) Bird seed aliens in Britain. Watsonia 15: 237-252.
Johnstone S.J.L. (2000) Cosmos. In: Cullen J. & al. (eds.), The European Garden Flora, vol. 6. Cambridge University Press, Cambridge: 658-659.
Kiger R.W. (2006) Cosmos. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 21. Oxford University Press, New York-Oxford: 203-205.
Verloove F. & Vandenberghe C. (1996) Nieuwe en interessante voederadventieven voor de Belgische flora, hoofdzakelijk in 1995. Dumortiera 66: 11-32.