Ireland: Kerry - Dublin - Cork - Waterford - Roscommon - Galway - Belfast
UK: London - Manchester - Newcastle - Cardiff - Liverpool
Water fern
Invasive Species Information
What Is Water fern - (Azolla filiculoides)?
Habitat: Still and slow flowing water bodies (e.g. ponds, drainage channels, ditches, canals).
Distribution in Ireland: Sparse distribution but locally abundant in some places.
Status: Established
Family name: Salviniaceae
Reproduction: Spreads mainly vegetatively though can produce minute spores.
Native to North and Central America and introduced for ornamental use in ponds and aquaria in Ireland. First recorded in 1883 and has spread in Ireland during the last 50 years.
Water Fern Leaves
Very small free-floating water plant that forms dense mats and complete coverage of the water in only a few months. Unmistakeable when in its red form and relatively easy to distinguish from duckweeds in its green form. Can be seen most months of the year.
How To Identify Water fern?
Colour: Green / Red
A sure method of distinguishing this species is to examine the trichomes on the upper surfaces of the leaves.
Trichomes are small protruberances that create water resistance. They are unicellular in Water ferns
Water Fern - Azolla filiculoides ID Guide
Water Fern Leaves
Water Fern Stand
Why Is Water fern A Problem?
Out-competes native species by forming a dense cover- ing on the surface of the water, blocking out light, causing deoxygenation, preventing air-breathing insects from reaching the surface and reducing water temperatures.
Dense and continuous stands can be a health hazard as the water surface appears solid.
Water Fern Stand (Red)
European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)
There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...
Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.
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American Skunk-Cabbage - Lysichiton americanus
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Red Alga - Grateloupia doryphora
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Waterweeds - Elodea (all species)
Additional Non-Native Plant Species identified as Medium Risk on Ireland's Biodiversity List...
Common name
Species name
Lysichiton americanus
Antithamnionella ternifolia
Ribes nigrum
Egeria densa
Buddleja davidii
Conyza canadensis
Codium fragile ssp. tomentosoides
Pseudotsuga menziesii
Solidago gigantea
Gunnera manicata
Persicaria wallichii
Lonicera japonica
Euphorbia esula
Acaena ovalifolia
Matteuccia struthiopteris
Sarracenia purpurea
Bunias orientalis
Environment
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