Rapistrum is a genus of two species. Both are originally native to the Mediterranean area, parts of Europe, western Asia, northern Africa and Macaronesia but have spread far beyond their native distribution range as weeds (which heavily blurred the boundaries of their original range).
Rapistrum perenne was more or less regularly seen between 1882 and 1919 and often persisted for some time. However, in modern times, only Rapistrum rugosum still occurs in Belgium.
Additional alien: Rapistrum perenne (L.) All. (E-Eur., W-As., grain and wool alien).
Schulz O.E. (1919) Rapistrum. In: Engler A. (ed.), Das Pflanzenreich 70(IV.105). Engelmann, Leipzig: 252-261.
Vasconcellos J.C. (rev. Akeroyd J.R.) (1993) Rapistrum. In: Tutin T.G. & al. (eds.), Flora Europaea (2nd ed.), vol. 1. Cambridge University Press, Cambridge: 414-415.