Landoltia punctata (G. Meyer) D.H. Les et D.J. Crawford) (syn.: Spirodela punctata (G. Meyer) C.H. Thompson, S. oligorrhiza (Kurz) Hegelmaier, Lemna punctata G. Meyer) (Austr., SE-As.) – An exceptional but possibly overlooked alien. It was discovered in 2007 as a common weed in the greenhouses in the National Botanic Garden in Meise.
Landoltia punctata is exceedingly similar to native Spirodela polyrrhiza (L.) Schleid. and likely to be confused with it. Fronds are usually more elliptic with less veins and less roots.
Selected literature:
Bratton J.H. (2010) Landoltia punctata (Lemnaceae) takes another step. BSBI News 113: 55.
Van Valkenburg J. & Pot R. (2008) Landoltia punctata (G. Mey.) D.H. Les & D.J. Crawford (Smal kroos), nieuw voor Nederland. Gorteria 33: 41-49.
Wiersema J.H. (2015) Application of the name Lemna punctata G. Mey., the type of Landoltia Les & D. J. Crawford. Plant Biol. (Stuttg.) 17, suppl 1: 5-9.