Azolla Lamarck. Mosquito Fern.

Key to Azolla

A small genus of about 6-9 species, floating aquatics, in tropical and warm temperate regions. The taxonomy and nomenclature of Azolla has been highly disputed and remains unsettled, with complex issues of taxon entitation and also great uncertainty about application of names with priority to the uncertainly entitated taxa. Sections shown in the key follow Metzgar, Schneider, & Pryer (2007). Azolla has a symbiotic, nitrogen-fixing cyanobacterium, Anabaena azollae Strasburger; the nitrogen-fixing capabilities of Azolla (through its symbiont) have resulted in its use as a fertilizer, green manure, and livestock feed, much promoted in recent years, but used historically in Asian rice paddies for centuries (Lumpkin in FNA 1993b).

ID notes: Very unfernlike, Azolla is a floating aquatic that looks superficially more like an aquatic liverwort, because of its very small (< 2 mm wide), bilobed leaves, borne in two ranks on either side of the stem. In some years and some places it occurs in great abundance, covering the surface of the water with a green or red mass of vegetation.

Ref: Bates & Browne (1981); Bunch & Hayden (2020); Evrard & Van Hove (2004); Lumpkin (1993) In Flora of North America Editorial Committee (1993b); Metzgar, Schneider, & Pryer (2007); Reid, Plunkett, & Peters (2006); Saunders & Fowler (1992). Show full citations.

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