Caylusea abyssinica (Fresen.) Fisch. et C.A. Mey. (syn.: Reseda abyssinica Fresen.) (E-Afr.) – A very rare and ephemeral alien. Apparently first recorded in a clearing in woodland in Wolvertem in 1981, possibly from pheasant feed. In 2012 also observed on a demolition site in Overpelt, among numerous birdseed aliens and in 2015 on the verge of a maize field in Lokeren, also obviously associated with birdseed waste.
There are rather few other alien records of Caylusea abyssinica in western Europe. It was formerly recorded in the port of Rotterdam in the Netherlands (van Ooststroom & Reichgelt 1960) and in the British Isles it has been grown from birdseed waste (Hanson & Mason 1985). In fact, further growing experiments (Hanson 2019) demonstrated that C. abyssinica is one of the frequent impurities in Niger seed.
Another species, Caylusea hexagyna (Forssk.) Green, was seen as an alien prior to 1930 in the British Isles (Clement & Foster 1994).
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Selected literature:
Clement E.J. & Foster M.C. (1994) Alien plants of the British Isles. BSBI, London: XVIII + 590 p.
Hanson G. (2019) Birdseed aliens originating from Niger (Guizotia abyssinica) wild bird food. British and Irish Botany 1(4): 292-308. [available online at: https://britishandirishbotany.org/index.php/bib/article/view/35]
Hanson C.G. & Mason J.L. (1985) Bird seed aliens in Britain. Watsonia 15: 237-252. [available online at: http://archive.bsbi.org.uk/Wats15p237.pdf]
Van Ooststroom S.J. & Reichgelt Th.J. (1960) Floristische notities 59-67. Acta Botanica Neerlandica 9: 197-207.