Azolla pinnata

Feathered mosquitofern

Nonnative to FloridaFederal Noxious Weed List Invasive

Species Overview

Native to: Africa and Madagascar, India, Southeast Asia, China and Japan, Malaya and the Philippines, the New Guinea mainland and Australia

Prohibited- Feathered mosquitofern (Azolla pinnata) is a small, nonnative, free-floating fern. The Azolla genus, which contains only 6 or 7 species, are the smallest ferns in the world. It was likely introduced by someone emptying their aquarium into a natural waterbody.

Species Characteristics

  • Family: Azollaceae
  • Habit: free-floating, aquatic fern
  • Leaves: minute, 1 -2 mm long, alternately arranged, upper lobe green, brown green or reddish, lower lobe translucent brown. 
  • Reproduction: spores and vegetative
  • Fruit: None
  • Distribution in Florida: limited 

Florida has one native species of AzollaAzolla filiculoides (previously known as A. caroliniana) or American waterfern. See image gallery above for a comparison of Azolla filiculoides and Azolla pinnata. A. pinnata is noticeably larger than A. filiculoides and appears triangular in shape – it has been compared to the shape of a Christmas tree.

Due to its invasive potential, feathered mosquitofern is not recommended by UF/IFASThe UF/IFAS Assessment lists Azolla pinnata as prohibited as it is listed on the Federal Noxious Weed List.


Feathered mosquitofern is a floating aquatic fern, found on the surface of small, still ponds or backwaters without wave action. Feathered mosquitofern spreads rapidly by vegetative growth and can form dense mats, interfering with boating, fishing and swimming. It becomes especially abundant in water with high nutrient levels, such as ponds in cattle and farm ponds, where it can completely cover the water's surface. It can block sunlight from reaching submersed plants and can also reduce oxygen levels in the water by blocking the interface between the water surface and the atmosphere. Azolla can survive on moist soil in and around rivers, ditches, and ponds, allowing it to survive dry periods.

Control Methods

Preventive Measures

Feathered mosquitofern is a prohibited species, do not keep this plant. 


Never empty aquarium or ornanmental pond contents into water bodies. Ensure gear is clean after boating or recreating in freshwater, so as not to transport plant material into new locations.


Small infestations may be removed using rakes or mesh nets. Floating booms may also used to consolidate infestations and remove with rakes. Larger infestations may be controlled with surface skimmers or surface suctions.


Stenopelmus rufinasus, a weevil native to Florida, is a specialist herbivore on North American mosquito ferns (Azolla spp.). This weevil has adopted Azolla pinnata as a source of food, which may prove useful as a control agent.


Diquat and Carfentrazone provide excellent control and Flumioxazin provides good control.

See this UF/IFAS EDIS Publication- Efficacy of Herbicide Active Ingredients Against Aquatic Weeds (Table 1) for more information.

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