Lemna turionifera Landolt (N-Am., temp. As.) – First discovered in 2005 but certainly neglected before (Van Landuyt 2007, Hoste & Bruinsma 2007). At present known from numerous areas in Flanders as well as in Wallonia but still poorly known.
Lemna turionifera is readily separated from L. minor by the combination of purple pigmentation and the production of turions (although both can very rarely lack in L. turionifera or be present in L. minor – such individual fronds are probably indistinguishable).
Lemna turionifera is supposed to be native in North America and temperate Asia. The first European records were – like for Lemna minuta – believed to date back to the 1960’s (Wolff & Orschiedt 1993) but recently Scandinavian records from the second half of the 19th century came to light (Wolff & Bruinsma 2005) and native status in (at least part of) Europe cannot be excluded.
Selected literature:
Ekman J. (2010) Röd andmat och japansk andmat funna i Uppland (Lemna turionifera and Lemna japonica coll. found in Uppland, southeast Sweden). Svensk Bot.Tidskr. 104: 377-378. [available online at: http://sbf.c.se/www/pdf/104%286%29/ekman.pdf]
Hohla M. (2012) Bromus sitchensis – neu für Österreich, Plantago coronopus - neu für Oberösterreich sowie weitere Beiträge zur Kenntnis der Flora des Innviertels. Stapfia 97: 180-192.
Hoste I. & Bruinsma J. (2007) Na Noord-Frankrijk en Nederland: Lemna turionifera nu ook in België ontdekt. Dumortiera 91: 20-22.
Hussner A. (2006) Die aquatischen Neophyten in Nordrhein-Westfalen. Decheniana 159: 39-50.
Ljungstrand E. (2010) Röd andmat påvisad i svensk natur (Lemna turionifera found in the wild in Sweden). Svensk Bot. Tidskr. 104: 3-7. [available online at: http://sbf.c.se/www/pdf/104%281%29/ljungstrand.pdf]
Van Landuyt W. (2007) Herkenning van de vier in België voorkomende drijvende Lemna-soorten. Dumortiera 91: 16-20.
Wolff P. & Bruinsma J. (2005) Knopkroos (Lemna turionifera Landolt) nieuw voor Nederland. Gorteria 31: 18-26.
Wolff P. & Landolt E. (1994) Spread of Lemna turionifera (Lemnaceae), the red duckweed, in Poland. Fragm. Flor. Geobot. 39: 439-451.
Wolff P. & Orschiedt O. (1993) Lemna turionifera Landolt – eine neue Wasserlinse für Süddeutschland, mit den Erstnachweisen für Europa. Carolinea 51: 9-26.