Ferny Azolla

Also known as:
Water Velvet
Africa, Asia, Australia

General description

Small, free-floating, mat-forming, aquatic fern < 3 cm long. Plant is triangular, with a straight midsection and pinnately arranged side branches. Roots are feather-like with fine rootlets. Leaves are minute, alternate, overlapping and green/red. Sporocarps are round and formed on the undersides of leaves.

What you need to know

Although ferny azolla is not a legally declared pest plant, it may still be invasive in some situations. Consider lower risk alternatives for your garden, such as native plants.

Lakes, ponds, wetlands, ditches, dams, slow-moving waterways.

Spores produced. Vegetative spread from fragmentation. Spores and fragments dispersed by water, waterfowl and wind. Human-mediated dispersal through movement of contaminated boats, equipment and machinery.

Forms dense mats, displacing native aquatic plants and reducing oxygen levels.

Site Management

Increasing shading over the waterway can reduce an infestation. Spraying aquatic weeds result in plants rotting in the water. This decreases dissolved oxygen in the water and in large amounts can kill aquatic life. Consider raking and only spraying regrowth in spring.

Recommended approaches

Physical control

Method: Rake onto dry land

Plant parts requiring disposal: All parts

Disposal options: Can be used as a fertiliser or mulch in the garden as it is high in nitrogen or can be fed to chickens


Biocontrol is currently not available for this species.

Community agrichemical control recommendations

Certified Handler/Experienced agrichemical user
Foliar spray emergent foliage with 100ml glyphosate green per 10L of water

CAUTION: When using any herbicide or pesticide please read the label thoroughly to ensure that all instructions and safety requirements are followed.

RPMP status

Not a legally declared pest plant
Hauraki Gulf Controlled Area Notice pest
Ferny azolla - Main species image