Asperula arvensis L. (Medit.) – A very rare and ephemeral alien. Already known at the beginning of the 19th century. According to Durand (1899) it was very rarely observed and usually ephemeral. In recent times Asperula arvensis is still sometimes seen, mostly as a grain alien, the last time apparently in the Antwerp port area in 2014.
The exact residence status of Asperula arvensis in Belgium (native vs. non-native) is obscure. It is considered a native species in Luxembourg and northeastern France, close to the Belgian frontiers, as a weed in agricultural fields. It has repeatedly been recorded in identical habitats in southern Belgium. It was not included in Verloove (2006).
Asperula arvensis and Sherardia arvensis are superficially similar and may be intermixed (both with inflorescences subtended by distinct involucral bracts and with bluish corollas). Moreover, near grain mills they are sometimes found growing side by side. Sherardia is distinguished by its persistent calyx that is enlarged in fruit and by its involucral bracts that are short bristly hairy along margins. In Asperula arvensis, in turn, a calyx is lacking in fruit and the involucral bracts are long ciliate.
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Selected literature:
Adema F. & Rauschert S. (1979) (464) Proposal to conserve 8485 Asperula L. (1753) with a conserved type species, A. arvensis L., against Asperula L. (1753) with the lectotype species A. odorata L. (Rubiaceae). Taxon 28(4): 422-423.
Durand T. (1899) Phanérogames. In: De Wildeman E. & Durand T., Prodrome de la flore belge. A. Castaigne Editeur, Bruxelles: 1112 p.
Verloove F. (2006) Catalogue of neophytes in Belgium (1800-2005). Scripta Botanica Belgica 39: 89 p.