What Ontario is doing

To prevent these unwanted invaders from coming into the province or spreading to new areas, Ontario has regulated all species in the genus Azolla as restricted invasive species under the Invasive Species Act.

Learn about the Invasive Species Act and regulations.

Background

Azolla is a genus (a group of related species) of free-floating water ferns, also known as mosquito ferns. There are approximately 7 species in the Azolla genus. They are found in freshwater habitats, often forming a dense green layer on the water’s surface. They are known for their nitrogen-fixing capabilities (ability to enrich the water with nutrients) and rapid growth, particularly in still or slow moving water bodies. Certain species within the genus, including Azollapinnata, Azolla mexicana and Azolla filiculoides have become invasive in parts of the world outside their native range.

Azolla species can tolerate a wide range of environmental conditions including:

  • salinities
  • pH
  • oxygen levels
  • temperature
  • pollution

Azolla species are considered ecosystem engineers. They can impact ecosystem processes and affect many species.

Azolla species can spread in a variety of ways including:

  • on the feet of waterfowl or shorebirds during migration
  • attached to watercraft or other equipment
  • illegal dumping of aquaria into waterways
  • flooding from other infested waterbodies
  • natural spread through connected waterbodies

Range

Azolla species are native to many parts of the world, from tropical to temperate zones. Some species have been introduced beyond their native ranges and have become invasive in parts of Europe, North America, New Zealand and Asia.

Ontario has one native species of Azolla (Azolla caroliniana). Other species in the genus are considered invasive and can cause harm in areas they invade. Because they look similar, all species in the genus are restricted in Ontario.

View an up-to-date distribution map of Azolla species.

Impacts of Azolla

In areas where Azolla populations have invaded, they can cover water surfaces, blocking out sunlight and reducing oxygen levels. This can harm all aquatic life in the ecosystem, reducing overall biodiversity. These dense mats of vegetation can:

  • impede boat navigation and fishing
  • reduce availability of water for agriculture by blocking irrigation pumps, or filling cattle and farm ponds
  • reduce water intake for municipal and industry uses, such as hydroelectricity generation

How to identify Azolla

Azolla species are small, floating ferns with branched leaves and roots which hang into the water. They are typically seen in large mats of floating vegetation that can quickly cover a water surface, sometimes giving it an appearance of dry land. They are usually green to reddish with tiny overlapping leaves, but identification varies by species.

What you need to know

  • Learn how to identify Azolla species and prevent the introduction or spread in Ontario’s waterways.
  • It is illegal to:
    • possess or transport any Azolla species in a provincial park or conservation reserve
    • bring any Azolla species into Ontario
    • deposit, release or propagate any Azolla species, including planting it or any other actions which may encourage its spread or growth
    • buy, sell, lease or trade Azolla species in Ontario
  • Never keep or use any Azolla species in an aquarium, water garden or for any other purpose. Be cautious when buying aquatic plants for ponds or aquariums, as Azolla species might be mixed with other plants.
  • Always clean, drain and dry your watercraft before transporting it to another waterbody. 
  • As of January 1, 2022, boaters must open or remove drain plugs and other devices to allow water to drain. They must also take reasonable measures to remove plants, animals and algae from their watercraft, watercraft equipment and trailer before transporting it overland. 
  • Boaters must ensure watercraft, watercraft equipment and trailers do not have aquatic plants, animals or algae attached to them before arriving at a launch site or placing the watercraft into any waterbody. 

Reporting illegal activity 

If you have any information about the illegal importation, distribution or sale of Azolla species, report it immediately to either:

If you’ve seen an Azolla species or another invasive species in the wild: