Trigonella procumbens (Besser) Reichenb. (syn.: T. besseriana Seringe nom. illeg., T. caerulea subsp. procumbens (Besser) Thell.) (EC and SE-Eur.) – A rare and ephemeral alien, formerly seen as wool and grain alien but much decreasing lately. Nearly all records were made between 1886 and 1922 (Verloove 2006). In 2016, however, recorded in three different localities near Ghent: at first on a demolition site, along with numerous other exceptional aliens like Glaucium grandiflorum, Trifolium sylvaticum, Vicia cuspidata, etc., subsequently on grain dumps in the port area (Rodenhuizedok and Sifferdok).
Trigonella procumbens is closely similar and obviously related to T. caerulea. According to some authors the latter is derived from it and more or less widely used for flavouring. Perhaps they are best accepted as subspecies of one variable species. In the Ghent port area T. procumbens was evidently introduced with cereals and fodder but it is unclear whether it is a contaminant or part of the fodder. In the British Isles it is a known (but much decreasing) grain alien (Stace 2010).
Selected literature:
Stace C. (2010) New flora of the British Isles, 3th ed.: XXXII + 1232 p. Cambridge University Press.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p. [available online at: http://alienplantsbelgium.be/sites/alienplantsbelgium.be/files/tabel_2.pdf]