The genus Salvinia includes twelve species such as S. molesta, S. auriculata, S. minima, and S. natans, which are small, floating, aquatic ferns native to warm tropical regions of the world, including Central and South America. S. natans, or floating watermoss, is native to Africa, Asia, and Europe. They are most used in North America in the water garden and aquarium trade. Salvinia species grow in open and still waters, flood canals, and other waterbodies and prefer full sunlight, warm, and nutrient rich waterbodies. When giant salvinia (S. molesta) was first introduced as an ornamental aquatic plant to California, it spread quickly to new waterbodies on boats and fishing gear. Salvinia species pose a significant threat to freshwater ecosystems as they can grow rapidly across water surfaces, forming dense floating mats that cut off light to other aquatic plants, reduce oxygen content and degrade water quality for fishes and other aquatic organisms. Because of its impact, giant salvinia is regulated in the US on the Federal Noxious Weed List.
Giant salvinia was first found in the wild in California in 1995. Since that outbreak was eradicated, it has been observed in 24 watersheds in Texas, California, Arizona, Louisiana, Mississippi, Alabama, Georgia, and Florida, as well as in the Great Lakes near New York and Massachusetts. Although no reports of Salvinia have been reported in Canada, given their proximity in the Great Lakes, they are at risk of being spread into Canada.
Impacts of Genus Salvinia
- Can easily be transmitted from waterbody to waterbody and grows aggressively to compete with native plants.
- Forms dense mats of floating vegetation, blocking available sunlight, reducing water quality and removing fish habitat.
- Mats can dislodge and cause stagnant waters as they decompose, killing native plants and animals.
- Dense mats can hinder recreational activities such as boating, angling and swimming.
How to Identify
- Free floating aquatic ferns with horizontal stems that float just below the surface.
- Leaves have hairs on the surface, and young leaves lie flat on the water while mature leaves are forced upright forming a long chain as the plant develops to create mats.
- Underwater root structure conceals stalks that can have infertile egg-shaped spore cases.
What You Can Do
- Learn how to identify Salvinia spp. and how to prevent the introduction or spread of these plants from your watercraft or fishing equipment.
- Never buy, plant, or keep Salvinia spp. in your aquarium or water garden. It is against the law to buy, sell, trade, possess, or transport Salvinia spp.
- Never deposit unwanted aquarium or water garden plants into Ontario’s lakes or rivers. Dispose of them in the garbage or at least 30 metres away from any waterbody.
- Clean, Drain, Dry your boat, trailer, and equipment after each use, be sure to remove all plants, animals, and mud before moving to a new waterbody.
- If you have any information about the illegal importing, distribution, or sale of Salvinia spp. , report it immediately to the MNRF at 1-877-847-7667, toll-free anytime. You can also call Crime Stoppers anonymously at 1-800-222-TIPS (8477).
OFAH/OMNRF Invading Species Awareness Program. (2023). Genus Salvinia. Retrieved from: www.invadingspecies.com.
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Header photo, ‘Salvinia Natans’ by KrzysztofZiarnek,Kenraiz | WikiMediaCommons