Water Fern

Invasive Species


Water fern (Azolla filiculoides), AKA Fairy Fern, is a very distinctive looking, small, floating, moss-like plant. The fern-like leaves are a bright green color with a thin red border. Water runs off the surface of the leaf.

The roots of water fern hang down into the water.

In winter or when exposed to stress, for example shade or low temperatures, whole leaves become red.


The free-floating water fern grows extremely fast and forms dense, up to 20 cm thick mats on canals, ponds, slow-flowing rivers, ditches, and wetlands.

All aquatic weeds present the following threats:

They form thick, dense mats that prevent light from reaching native plants and can be mistaken for solid ground by children and animals.

The thick mats also prevent oxygen from entering the water, drastically reducing oxygen levels, which may kill fish and other aquatic life.

A large infestation greatly reduces access for recreational water activities.

Mats of aquatic weeds often result in a bad smell and reduced visibility in the water.

Dense mats can reduce the flow of water and increase the risk of flooding.


Check, clean and disinfect all equipment, boots, wheels and anything that made contact with the water. This will ensure you don’t carry fragments to other possible habitats.

The control of large infestations of aquatic weeds will require the services of an appropriately certified invasive species control company.


If you encounter water fern please enter the details into our log.