Red Duckweed (Lemna turionifera Landolt) new to Britain

In May 2007, red duckweed (Lemna turionifera) was found in a ditch at Stoborough in Dorset. In July 2007, a second population was found in the South Forty-Foot Drain in Lincolnshire. L. turionifera is native in North America and northern Asia. It has also been recorded from Austria, Belgium, the Czech Republic, France, Germany, the Netherlands, Norway, Poland and Sweden where it has usually been considered to be an alien. Its occurrence in two very widely separated sites suggests that it may have been in Britain for some time but has been overlooked. Notes are provided to aid identification of L. turionifera, particularly in relation to L. minor and L. gibba and some information is provided on the habitats and species associated with it at its two British sites.