kids encyclopedia robot

Azolla cristata facts for kids

Kids Encyclopedia Facts
Quick facts for kids
Azolla cristata
Azolla cristata winter color 001.jpg
Azolla cristata (reddish) and Lemna (green) in a small pool
Conservation status

Secure (NatureServe)
Scientific classification

Synonyms of A. cristata include:

  • Azolla mexicana Schlecht. & Cham.
  • Azolla portoricensis Spreng.
  • Azolla microphylla Kaulf.
  • Azolla densa Desv.
  • Azolla bonariensis Bertol.
  • Salvinia azolla Raddi

Azolla cristata , the Carolina mosquitofern, 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.

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. It is able to fix nitrogen from the air by means of symbiotic cyanobacteria. It can survive winter water temperatures of 5 °C(41 degrees Fahrenheit), with optimum summer growth between 25–30 °C. (77-86 degrees Fahrenheit)

Azolla caroliniana1
Frond detail
Azolla caroliniana
Azolla cristata at Jack London State Historic Park


The only sure method of distinguishing this species from Azolla filiculoides is to examine the trichomes on the upper surfaces of the leaves. Trichomes are small protuberances that create water resistance. They are unicellular in A. filiculoides but septate (two-celled) in A. cristata.


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

Cultivation and uses

Azolla cristata is of commercial importance in cultivation in southern and eastern Asia as a bio-fertilizer, valued for its nitrogen-fixing ability, which benefits crops such as rice when the fern is grown under it and reduces the need for artificial fertilizer addition. The thick mat of fronds (up to 4 cm thick) also suppresses weed growth. Harvested fronds are also used as a food for fish and poultry. 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.

kids search engine
Azolla cristata Facts for Kids. Kiddle Encyclopedia.