Cyperus congestus Vahl [syn.: Mariscus congestus (Vahl) C.B. Clarke] (S-Afr.) – A rare and ephemeral alien. Formerly the most regularly introduced species of Cyperus in the valley of river Vesdre (wool alien), but long confused with other species (Lambinon 1995). Recorded at least between 1886 and 1959, possibly sometimes persisting for some years and often in relative abundance. Only exceptionally seen elsewhere, for instance near Antwerpen (Hoboken) in 1915, without obvious vector of introduction (pond margin). Discovered on a ground heap near a garden center in Dadizele in 2008 (a single specimen). Also sometimes seen as an escape from the collections in the National Botanic Garden in Meise. A young plant, discovered on a railway yard where wagons with cereals were stored in Izegem in 1998, possibly also belongs to Cyperus congestus. Cyperus congestus is originally native in South Africa but more or less widely naturalized elsewhere (including parts of southern Europe). Recent Belgian records probably originate from the species’ secondary distribution area.
Selected literature:
Lambinon J. (1995) Notes taxonomiques, nomenclaturales et chorologiques relatives à la quatrième édition de la « Nouvelle Flore » de la Belgique et des régions voisines. 3. Données nouvelles sur des plantes adventices ou subspontanées en Belgique. Dumortiera 60: 1-36.