Alternative common names:
Feathered mosquito fern and water velvet.
The mosquito fern is an aquatic plant that floats on the surface of the water. It only grows in slow-moving water bodies because swift currents and waves break up the plant. It can spread very quickly by forming dense vegetative masses on areas of still water. This limits the light available to other aquatic plants and oxygen used by other aquatic life.
Where does this species come from?Africa, Madagascar, India, Southeast Asia, China, Japan, Malaysia, the Philippines, the New Guinea mainland and Australia.
What is its invasive status in South Africa?NEMBA Category 1b.
Where in South Africa is it a problem?Eastern Cape.
How does it spread?It is spread by water birds, water sport tackle (diving, fishing, water skiing) or by discharge by aquarium keepers.
Why is it a problem?
It forms dense vegetative masses on areas of still water and spreads very quickly. This limits the light available to other aquatic plants and oxygen used by other aquatic life.
What does it look like?
Mosquito fern is a small plant, 1.5-2.5cm long, with a straight main axis and pinnately arranged side branches, which are progressively longer towards the base, making it roughly triangular in shape. The basal branches themselves become pinnate and eventually fragment as the main axis decomposes to form new plants.
Leaves: The leaves are 1-2mm long, overlapping in two ranks. The upper lobe is green, brownish-green or reddish; the lower lobe is translucent brown. Short, cylindrical, unicellular hairs often present on the upper lobes.
Does the plant have any uses?
The genus Azolla is useful in rice fields because it can assimilate atmospheric nitrogen gas owing to the nitrogen fixation by cyanobacteria (blue-green alga) living in the cavities located at the lower side of the upper (dorsal) lobes of the leaf.