Azolla is a floating water fern that has a symbiotic relationship with a nitrogen-fixing bacteria. It floats on the surface of water by means of numerous, small, closely-overlapping scale-like leaves, with their roots hanging in the water. It can produce large amounts of anthocyanins in bright sunlight, creating an intense red color and causing the water surface to appear to be covered with a red carpet. Azolla can reproduce asexualy by breaking off. Each branch that breaks off forms a new plant. Azolla can also reproduce sexually. Like all ferns, Azolla produce spores.
Azolla has reportedly been used as a feed for pigs and ducks in SE Asia; for cattle, fish and poultry in Vietnam; and for pigs in Singapore and Taiwan. It is described as an excellent substitute for green forage for cattle in Vietnam and may replace up to 50% of the rice bran used as feed for pigs in that country. Although very low in DM, it contains a high level of protein (24% CP). The amino acid composition of Azolla compared well with reference protein sources.
Azolla has been used as a green manure crop in Vietnam and China for centuries. The ability of azolla to shade out weeds in wetland rice and taro has been noted by farmers and researchers since the early 20th century.