Water Fern (Azolla filiculoides)



Water fern (Azolla filiculoides)

Photo courtesy of GB Non Native Species Secretariat

To view NBN location data click here



  • Forms dense rafts and outcompetes native plant species.
  • Reduced light levels below the rafts can cause die off of waterweeds and algae and reduce water oxygenation levels.
  • Deoxygenates water killing fish and other fauna.
  • Blocks water bodies and may lead to an increased risk of flooding.
  • Garden and aquaria trade
  • Discarded garden or pond waste and flood events.



Should not be released in the wild. Dispose of garden and pond waste responsibily. Check vehicles, boats, equipment and clothing for plant fragments when leaving infested sites and clean if necessary.

Physical Control

Is difficult as it reproduces by fragmentation and, in rivers, these fragments float downstream,

Chemical Control

Herbicides with glyphosate as the active ingredient can be used and are effective but expensive and kill other plants (including native species) that they contact. More information on control measures is avaiable from the Centre for Ecology and Hydrology, Centre for Aquatic Plant Management Information Sheet (Click here to download)

Note all chemical treatments must be licensed by SEPA.

Biological Control

(using the weevil Stenopelmus rufinasus) can be extremely effective in controlling infestations. The weevil has been present for so long in Britain that there are no restrictions on release. Will require repeated introduction of the weevil in recurring cases as it does not persist.


Non Native Species Secretariat identification guide

Non Native Species Secretariat Fact Sheet

SNH SAF Training Manual

Invasive Species Ireland Fact Sheet

Daisie Species Fact Sheets

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