New records of aquatic plants in Germany
The three following plants have been found naturalized in the wild in Germany:
- Myriophyllum heterophyllum (Haloragaceae) originates from North America. It is only considered a weed by the Global Compendium of Weeds. It has been known to occur in Eastern Germany since the 1960s but today, several occurrences in the wild have been recorded in Western Germany. Dense stands have been found in shallow lakes in Nordrhein-Westfalen. These populations have been mechanically controlled as they were considered a threat (Hussner et al. 2005). This plant is thought to have the potential to become invasive, especially in shallow lakes and channels (A Hussner, pers. comm.).
- Hygrophila polysperma (Acanthaceae) originates from Asia and frequently enters the EPPO region for aquarium purposes. According to the Global Compendium of Weeds, this plant has already been recorded elsewhere in the world as a noxious weed, a quarantine weed and an environmental weed. In Germany, the plant has been found naturalized in the Erft river in 2005 and in Lake Fühlingen in 2006. In the Erft river, it forms small and large populations on more than 10 km of the river, and appears to be the most widespread plant there. Moreover, the plant seems to overwinter in gardens and in ponds in Düsseldorf (A Hussner, pers. comm.).
- Saururus cernuus (Saururaceae) originates from North America and frequently enters the EPPO region for ornamental purposes. According to the Global Compendium of Weeds, this plant has already been recorded elsewhere in the world as a quarantine weed. The plant was first recorded in Germany in 2004 by Swatek et al. (2004) in its emerged growth form at the edge of a pond in a forest in Duisburg-Mülheim (Nordrhein-Westfalen). Swatek et al. (2004) described the population as small, circa 20 shoots, but the plants flowered and look vigorous.
These three aquatic plants are imported into the EPPO region (see RS 2007/016) and represent a risk.
A Global Compendium of Weeds: http://www.hear.org/gcw/alpha_select_gcw.htm
Andreas Hussner, Heinrich-Heine-Universität Düsseldorf, firstname.lastname@example.org
Hussner A, Josephs M ; Schmitz U (in press) [About Hygrophila polysperma (Roxb.) T. Anderson and Pontederia cordata L. in North Rhine-Westphalia] (Über Hygrophila polysperma (Roxb.) T. Anderson und Pontederia cordata L. in Nordrhein-Westfalen). Floristische Rundbriefe 40. (in German)
Hussner A (2006) [Alien aquatic plants of North Rhine-Westphalia] (Die aquatischen Neophyten in Nordrhein-Westfalen). Decheniana 159: 39-50. (in German)
Hussner A (2005);[Distribution of alien aquatic plants in the river Erft (North Rhine-Westphalia)];(Zur Verbreitung aquatischer Neophyten in der Erft, Nordrhein-Westfalen). Frankfurter Geobotanische Kolloquien 19: 55-58. (in German)
Hussner A, Nienhaus I ; Krause T (2005) [Distribution of Myriophyllum heterophyllum Michx. in North Rhine-Westphalia] (Zur Verbreitung von Myriophyllum heterophyllum Michx. in Nordrhein-Westfalen). Floristische Rundbriefe 39: 113-120. (in German)
Swatek JH,;Loos GH, Keil P ; Haeupler H (2004) [Saururus cernuus L. in;the forest;between Duisburg-Mühlheim (Ruhr area)] (Saururus cernuus L., das Eidechsenschwänzchen, im Duisburg-Mülheimer Wald (Westliches Ruhrgebiet, Nordrhein-Westfalen). Floristische Rundbriefe 38: 39-44. (in German).