Azolla is a plant that also has special powers. But those same powers have created a global weedy pest.

Azolla is a genus of plant with several species that grow very quickly under the right conditions and can double their biomass in as little as two days. That's superhero speed. Tolerant of a wide range of conditions, they can also live in polluted places where other organisms cannot survive.

Their habitats also includes sites low in nitrogen because they share a special relationship with a blue-green alga, known scientifically as cyanobacteria. Its special microscopic friend - the cyanobacteria - takes nitrogen out of the environment and converts it to a form that is usable to the plant.

The high nitrogen in the plant makes it a useful biofertilizer and it is grown in Asia for this reason.

Its potential uses also provide shelter to aquatic animals, weed suppression, food, biofuels and water treatment. Azolla can grow in and uptake heavy metals like uranium, which makes them a useful tool for restoring polluted freshwater environments.

Azolla's tolerance and rapid growth has allowed it to penetrate into new places and it now lives all over the world in freshwater environments such as rivers and wetlands.

You might not guess from a quick look but Azolla are an aquatic fern, plants that do not flower or seed but reproduce through spores.

Each plant is small at 1-2.5 cm and floats on top of the water surface. Under conditions of high phosphorus, they can bloom creating thick mats up to 20cm in depth and covering vast areas of water reducing sunlight and cooling the water.

If you are in a river or stream with Azolla around, make sure you clean your equipment before moving onto the next site and contact your local council weeds officer for more information.