Azolla is a small, taxonomically difficult genus from warm-temperate and subtropical zones. About seven species are usually recognised, including three New World species, but some are probably better lumped. Evrard & Van Hove (2004) recently merged Azolla caroliniana Willd. and A. filiculoides.

The exact origin of the Belgian populations remains uncertain. It was probably initially introduced as an ornamental.


Evrard C. & Van Hove C. (2004) Taxonomy of the American Azolla species (Azollaceae): a critical review. Syst. Geogr. Pl. 74: 301-318.

Lumpkin T.A. (1993) Azollaceae. In: Flora of North America Editorial Committee (eds.), Flora of North America, vol. 2. Oxford University Press, New York-Oxford: 338-342.

Sotiaux A. (1979) Contribution à une meilleure connaissance du genre Azolla dans le territoire de la Nouvelle Flore. Dumortiera 13: 1-5.

Zimmerman W.J., Lumpkin T.A. & Watanabe I. (1989) Classification of Azolla spp., section Azolla. Euphytica 43: 223-232.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith