Zizania latifolia (Griseb.) Turcz. ex Stapf (As.) – A very rare escape from or relic of cultivation. Recorded on the margins of an exposed pond (Le Grand Etang) near La Hulpe in 2009 (see http://waarnemingen.be/waarneming/view/44769819), doubtlessly as a relic of former cultivation. In identical circumstances also discovered in Lummen (Laambeekvallei) in 2015. In 2010 furthermore seen in a city canal in Gent (a single plant), most likely as an escape. Apparently established also alongside a canal in Moerbeke since 2017.
Zizania latifolia is very reluctant to flower and might therefore pass unrecorded. It is characterised as follows: up to 200 cm tall, stem spongy and up to 20 mm wide, leaves sword-like, up to 50 mm wide, sharply serrate at margin and main vein, etc. With this combination of characters it cannot be mistaken for other Poaceae in Belgium.
Up to present it seems that Zizania latifolia persists well in Belgium but hardly expands. However, in some parts of Europe invasive behaviour has been reported, for instance in Lithuania (see Liatukas & Stukonis 2009). There, Zizania latifolia was spotted in the Dotnuvėlė stream since 2006. A detailed investigation showed that it was most vigorous in the communities of class Phragmito-Magnocaricetea. Zizania latifolia forms monodominant stands and covers an area of ca. 2500 m2. It successfully out-competes Phragmites australis and other less abundant species. Similar invasive behaviour has been reported for instance from New Zealand where its introduction is prohibited (Terrell 2007).
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Selected references:
Clement E.J. (2000) More about Zizania latifolia. BSBI News 83: 40-41.
Hagen A.R., Giese H. & Brochmann C. (2002) Zizania latifolia (Poaceae) found at another site in West Sussex. BSBI News 91: 49-50.
Hollings M. & Hollings O. (2000) Zizania latifolia – fit and flourishing over-abundantly in a West Sussex pond. BSBI News 85: 39-40.
Liatukas Ž. & Stukonis V. (2009) Zizania latifolia – a new alien plant in Lithuania [Zizania latifolia – naujas svetimžemis augalas Lietuvoje]. Botanica Lithuanica 15(1): 17-24.
Page K.W. (2000) Zizania latifolia (Poaceae) naturalized in Surrey (v.c. 17). BSBI News 84: 38-39 (+ frontcover).
Terrell E.E. (2007) Zizania. In: Barkworth M.E. & al. (eds.), Flora of North America north of Mexico, vol. 24: 47-51. Oxford University Press, New York-Oxford.