Notes: FNA2: "Agriculturally, Azolla is famous for its symbiosis with the nitrogen-fixing Anabaena azollae Strasburger, a cyanobacterium (blue-green alga) found at the stem apices, beneath indusia, and in cavities of the upper leaf lobes. Because the plants fix nitrogen, they are often used as a green fertilizer or mixed with livestock feed as a nutritional supplement. Azolla pinnata has been cultivated for many centuries in rice paddies of northern Vietnam and southeastern China, where it acts as a fertilizer after it decomposes.

Azolla is the most frequently studied genus of ferns in the world because of its economic importance. The three North American species are naturalized in Europe and South Africa, and they have been introduced into Hawaii for horticulture and into Asia for agriculture. All species have been studied for agricultural uses in rice-producing areas.

Azolla is usually found in stagnant or slow-moving water of ponds, lakes, marshes, swamps, and streams. Plants turn reddish when under stress, such as from poor nutrition, salinity, or high temperatures. Sporulation needs further investigation."

References:

Family information last updated 9/4/2012 by David Giblin.