Trifolium resupinatum L. (incl. var. majus Boiss., syn.: T. suaveolens Willd., T. resupinatum var. suaveolens (Willd.) Dinsm., T. resupinatum subsp. suaveolens (Willd.) Ponert) (Medit., W-As.) – A regular but usually ephemeral alien (erroneously accepted as more or less naturalized by Lawalrée 1961). Apparently first recorded in the wild in Belgium around 1860. In the 19th century mostly seen as an impurity in clover- or alfalfa fields or near grain mills. Between 1894 and 1950 also repeatedly seen as a wool alien in the valley of river Vesdre. In the past decades still frequently seen. However, recent records are often (issued from) deliberate introductions, often in or near recently sown road verges, canal banks, etc. These plants are more vigorous with thick, hollow stems and larger heads and leaflets and are usually referred to as var. majus (see also Brugge-Timm 1969, Parent 1974, Walsemann & Walsemann 2004). Trifolium resupinatum also still occurs near grain mills or on dumps. In 1994 and 1995 it was recorded from a demolition site of a former horse artillery in Gent, obviously from a long-buried seed bank (Verloove & Heyneman 2012). A record from an exposed seed bank in the sea dunes between De Panne and Koksijde (Fluithoek) in 2009 could also be explained as such. Trifolium resupinatum was repeatedly recorded in the very same area, at least between 1916 and 1919 (initially introduced with horse fodder). Since 2016 it has also been recorded on several occasions in disturbed lawns in camping sites, especially in coastal areas. In some of these localities it occurs in relatively large, more or less established populations.
Cultivated plots with Trifolium resupinatum used to harbour a species-rich alien flora in Central-Europe (see for instance Gerstberger 1977, Lienenbecker 1979, Raabe 1980, Randig 1989).
Selected literature:
Gerstberger P. (1977) Silene concoidea L. in der Begleitflora von Trifolium resupinatum L. im Rheinland. Göttinger Flor. Rundbr. 10(4): 91-94.
Haerinasab M. & Rahiminejad M.R. (2012) A Taxonomic Revision Of The Genus Trifolium L. Sect. Fragifera Koch (Fabaceae) In Iran. Iranian Journal of Botany 18(1): 22-30. [available online at: https://www.researchgate.net/publication/265844832_A_TAXONOMIC_REVISION_...
Lienenbecker H. & Raabe U. (1979) Adventivarten in Trifolium resupinatum-Äckern in Ostwestfalen. Göttinger Floristische Rundbriefe 13: 22-23.
Parent G.H. (1974) Note sur une récolte récente de Trifolium resupinatum L. en Belgique. Nat. Mosana 27(1-2): 29-31.
Raabe U. (1980) Weitere Funde der Blasenmiere (Lepyrodiclis holosteoides (C.A.Mey.) Fenzl. ex Fisch. & Mey.) in Trifolium resupinatum-Äckern. Natur und Heimat 40: 87-89.
Randig W. & Brandes D. (1989) Adventivarten in Trifolium resupinatum-Äckern in Niedersachsen. Floristische Rundbriefe 23(1): 52-53.
Verloove F. & Heyneman G. (2012) Merkwaardige plantencollecties van twee antropogene zaadbanken in Gent (Oost-Vlaanderen, België). Dumortiera 100: 19-24. [available online at: http://www.br.fgov.be/DUMORTIERA/DUM_100/Dum%20100_19-24_Zaadbanken%20Gent-Verloove%20en%20Heyneman.pdf]
Walsemann E. & Walsemann H. (2004) Der Hohlstängelige Klee Trifolium suaveolens Willd. Kiel. Not. Pflanzenknd. 32: 101-102.