Juncus foliosus Desf. (syn.: J. bufonius L. var. major Boiss.) (SW-Eur., N-Afr.) – A very rare and local species, known at least since 1984 from muddy banks and exposed fish ponds in Midden-Limburg (Vannerom 1984). Perhaps overlooked elsewhere (due to confusion with Juncus bufonius). The exact residence status of Juncus foliosus in western Europe is very uncertain. It is often claimed as an overlooked native species (see for instance Sell & Murrell 1996, Stace 1997). Recently also discovered in the Netherlands and Scandinavia; see van der Meijden 2005, Johnsen 1987). All Belgian populations are confined to fishponds in a relatively small area in Midden-Limburg (at present at least 17 locations according to Berten 2006). Juncus foliosus apparently occurred simultaneously with the introduction of fish from southern and eastern Europe, along with several other neophytes viz Lemna minuta and Lindernia dubia (Berten l.c.). At least for the time being it is therefore considered to be a xenophyte in Belgium. After its initial introduction it was probably further spread (locally) by waterfowl.
Juncus foliosus much resembles native J. bufonius and both are possibly confused. In addition to the characters presented in the key, Juncus foliosus usually has remarkably fleshy leaves: when crushed they make a crispy sound and spread a cucumber-like odour.
Selected literature
Berten B. (2006) Juncus foliosus. In: Van Landuyt W., Hoste I., Vanhecke L., Van den Bremt P., Vercruysse W. & De Beer D., Atlas van de Flora van Vlaanderen en het Brussels Gewest. Instituut voor natuur- en bosonderzoek, Nationale Plantentuin van België en Flo.Wer: 505.
Cope T.A. & Stace C.A. (1978) The Juncus bufonius L. aggregate in Western Europe. Watsonia 12: 113-128.
Johnsen J. (1987) Juncus foliosus, et nytt siv i Skandinavia. Blyttia 45(2): 65-67.
Saule M. & Vivant J. (1989) Sur la présence de Juncus foliosus Desf. dans les Landes méridionales. Bull. Soc. Bot. Fr., Lett. Bot. 136: 335-338.
Sell P.D. & Murrell G. (1996) Flora of Great Britain and Ireland. Vol. 5. Cambridge University Press, Cambridge: 410 p.
Stace C. (1997) New flora of the British Isles, 2nd ed.: XXVII + 1130 p. Cambridge University Press.
Van der Meijden R. (2005) Heukels’ Flora van Nederland (23e druk). Wolters-Noordhoff, Groningen: 685 p.
Vannerom H. (1984) Juncus foliosus Desf., nieuw voor de Belgische flora in Genk (Limburg, België). Dumortiera 29-30: 59-60.
Verloove F. (2002) Ingeburgerde plantensoorten in Vlaanderen. Mededeling van het Instituut voor Natuurbehoud n° 20: 227 p.