Azolla_cristata
Azolla cristata
Species of aquatic plant
Azolla cristata , the Carolina mosquitofern,[3] Carolina azolla or water velvet, is a species of Azolla native to the Americas, in eastern North America from southern Ontario southward, and from the east coast west to Wisconsin and Texas, and in the Caribbean, and in Central and South America from southeastern Mexico (Chiapas) south to northern Argentina and Uruguay.[4]
It is a freshwater aquatic fern, with scale-like fronds 5–10 mm long, green to reddish, most often reddish in strong light and in winter. They are covered in tiny protuberances called trichomes that give it the appearance of velvet.[5][6] It is able to fix nitrogen from the air by means of symbiotic cyanobacteria. It can survive winter water temperatures of 5 °C (41 °F), with optimum summer growth between 25–30 °C (77–86 °F).[7]