''Azolla cristata'', the Carolina mosquito fern, Carolina azolla, or water velvet, is a species of the ''

Azolla ''Azolla'' (common called mosquito fern, water fern, and fairy moss) is a genus of seven species of aquatic ferns in the family Salviniaceae. They are extremely reduced in form and specialized, having a significantly different appearance to ot ...

'' genus native to the

Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...

, in eastern

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

from southern

Ontario Ontario is the southernmost Provinces and territories of Canada, province of Canada. Located in Central Canada, Ontario is the Population of Canada by province and territory, country's most populous province. As of the 2021 Canadian census, it ...

southward, from the east coast west to

Wisconsin Wisconsin ( ) is a U.S. state, state in the Great Lakes region, Great Lakes region of the Upper Midwest of the United States. It borders Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michig ...

and

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

, the

Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...

, and in Central and

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

from southeastern

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

(

Chiapas Chiapas, officially the Free and Sovereign State of Chiapas, is one of the states that make up the Political divisions of Mexico, 32 federal entities of Mexico. It comprises Municipalities of Chiapas, 124 municipalities and its capital and large ...

) south to northern

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and

Uruguay Uruguay, officially the Oriental Republic of Uruguay, is a country in South America. It shares borders with Argentina to its west and southwest and Brazil to its north and northeast, while bordering the Río de la Plata to the south and the A ...

. It is a

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...

aquatic

fern The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...

, with scale-like

frond A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

s 5–10 mm long, green to reddish, most often reddish in winter and in strong light. They are covered in tiny

trichome Trichomes (; ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a plant ...

s that give it the appearance of velvet.Flora of North America
''Azolla cristata ''
/ref>Aquatic Plant Information System

It is able to fix nitrogen from the air by means of

symbiotic Symbiosis (Ancient Greek : living with, companionship < : together; and ''bíōsis'': living) is any type of a close and long-term biolo ...

cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...

. It can survive winter water temperatures of , with optimum summer growth between .NESAC
Package of Practice for Azolla
/ref>

Identification

Distinguishing this species from '' Azolla filiculoides'' involves examining the trichomes (small bumps that create water resistance) on the upper surfaces of the leaves. They are unicellular in ''A. filiculoides'' but septate (two-celled) in ''A. cristata''.

Name

This species has erroneously been known under the name ''Azolla caroliniana''. However, research by Evrard and Van Hove found that the type specimen of ''A. caroliniana'' actually consists of plants of ''Azolla filiculoides'' and so the name ''caroliniana'' has been improperly applied to this species.

Cultivation and uses

''A. cristata'' is of commercial importance in cultivation in southern and eastern

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

as a

biofertilizer A biofertilizer is a substance containing living micro-organisms which, when applied to seeds, plant surfaces, or soil, colonize the rhizosphere or the interior of the plant and promotes growth by increasing the supply or availability of primary n ...

, valued for its nitrogen-fixing ability, which benefits crops such as

rice Rice is a cereal grain and in its Domestication, domesticated form is the staple food of over half of the world's population, particularly in Asia and Africa. Rice is the seed of the grass species ''Oryza sativa'' (Asian rice)—or, much l ...

when the fern is grown under it and reduces the need for

artificial fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...

. The thick mat of

fronds A frond is a large, divided leaf. In both common usage and botanical nomenclature, the leaves of ferns are referred to as fronds and some botanists restrict the term to this group. Other botanists allow the term frond to also apply to the lar ...

(up to 4 cm thick) also suppresses weed growth. Harvested fronds are also used as a food for

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

and

poultry Poultry () are domesticated birds kept by humans for the purpose of harvesting animal products such as meat, Eggs as food, eggs or feathers. The practice of animal husbandry, raising poultry is known as poultry farming. These birds are most typ ...

. It is also often used as a floating plant in both coldwater and tropical aquaria, as well as in outdoor ponds; it is propagated by division.Hiscock, P. (2003). ''Encyclopedia of Aquarium Plants''. Interpret Publishing, United States and Canada .

References

External links

The Azolla Foundation
A website dedicated to the distribution of Azolla for propagation as alternative livestock feed. {{Taxonbar, from=Q981134 Salviniales Freshwater plants Ferns of the Americas Flora of the Northeastern United States Flora of Southern America Plants described in 1810 Flora of the Southeastern United States Flora of the North-Central United States Flora of Texas