Trifolium rubens L. (C and S-Eur.) – A very rare and probably ephemeral alien (possibly sometimes temporarily persisting). Confirmed records from the 19th century are available from Bois de Mont (1890), Jalhay and Herselt/Aarschot. Records from the latter locality are possibly dubious (other collections with the same citation belong to the similar but native Trifolium medium). In the 20th century collected three times: in 1922 on waste land near Liège (Sclessin), in 1960 on an arid hill side in Dourbes (scattered specimens, apparently in a quite natural habitat) and in 1965 in a road verge near Chaumont.
Trifolium rubens is native in Luxembourg and northern France, close to the Belgian frontiers (Pierrot & al. 1906). Collections from woodland between Montmédy and Torgny (1908) are doubtlessly native but are situated in France. Trifolium rubens is here confirmed for the first time from Belgium (some records were initially wrongly identified as T. alpestre; others apparently remained unpublished so far). Assessing its exact residence status requires further research but the records from Dourbes and Chaumont could as well be native.
Lawalrée (1961) has obviously intermixed Trifolium alpestre, T. medium and T. rubens. All three are much alike in general habit and might still be confused. However, Trifolium alpestre and T. rubens are readily distinguished by their 20-veined calyces.
Selected literature:
Lawalrée A (1961) Papilionaceae. In: Robyns W. (ed.), Flore Générale de Belgique, vol. 4, fasc. 1. Jardin Botanique de l’Etat, Bruxelles: 9-134.
Pierrot P., Cardot J. & Vuillaume A. (1906) Catalogue des plantes vasculaires de l’arrondissement de Montmédy. Imprimerie G. Pierrot, Montmédy: 532 p.