Fanwort

  • Fanwort

    (Cabomba caroliniana)

    Fanwort is an invasive aquatic plant native to the southeastern United States and parts of South America. Commonly sold as an aquarium plant, it was first observed at Kasshabog Lake in the Crowe River watershed north of Peterborough in 1991. Since its arrival, it has spread to other areas within the watershed — the North River, South Lake and Mountain Lake. An aggressive plant that forms huge colonies of dense mats under or at the surface of the water body, it is most often found in quiet waters usually less than three metres deep but up to five metres in Ontario.

    Fanwort is a perennial plant that reproduces primarily by regeneration of stem fragments or rhizomes even though it flowers from May to September. A small piece of stem or rhizome can regenerate into a whole new plant which can spread across a vast area in a short time period. Seed production is rare and being examined to determine methods of control. Preferring acidic water with a pH of 4.8 to 7.8, the plant tolerates cold temperatures and stays green all year long.

    Control methods include mechanical harvesting, draw downs of water levels to expose plants and herbicides. Harvesting may cause fragmentation which could create new infestations downstream.

     

    Range

    Fanwort is found in the northeastern United States, with an isolated population in the Crowe River watershed northeast of Peterborough.

  • Identification

    • Although Fanwort looks like other aquatic plants in Ontario, such as bladderwort (Utricularia vulgaris), white-water crowfoot (Ranunculus aquatilis), northern water-milfoil (Myriophyllum sibiricum), water marigold (Megalodonta beckii) and coontail (Ceratophyllum demersum), it is distinguished by opposite, finely divided, fan-shaped leaves located on distinct stems.
    • It is a submerged plant that roots on the water bottom, has fan-shaped leaves growing underwater on opposite sides of the main stem and small floating oblong leaves up to 3 cm long on the water surface. The leaves vary in colour from bright to olive green to reddish brown.
    • The 0.6 to 1.5-cm wide flowers usually grow above the surface of the water from late spring to early fall with white to pale yellow petals, sometimes with a tinge of purple or pink. The flowers form 2 to 4 leathery pods which contain 1 to 3 seeds.

    Impact

    • An extremely persistent invasive plant, Fanwort can form dense underwater stands that displace native plants, disrupt fish communities, clog drainage canals and streams and interfere with swimming and boating.
    • It can also reduce water storage capacity and taint drinking water supplies.
    • Sediments increase in water bodies with Fanwort infestations.
    • Due to its preference for acidic water, the plant could spread to the Canadian Shield which abounds with acidic lakes.

    How can you help?

    If you see Fanwort or a plant that you think might be this invader, report it on the toll-free Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) and report it to your local Lands or Natural Resources officer. Be sure to include understandable directions to the location.

    • Learn to identify Fanwort and how to prevent spreading this plant with your watercraft.
    • Avoid the infested areas in the Crowe River watershed or reduce your speed when travelling near infestations because Fanwort fragments may break off and spread to new areas.
    • Inspect your boat and equipment and remove any plants, animals or mud before leaving a water body.
    • Avoid planting Fanwort in your aquarium or water garden; use only native or non-invasive plants.
    • Do not release aquarium plants or pets into any waterbody.
    • If you see Fanwort or a plant that you think might be this invader, report it on the toll-free Turtle Island Invaders hotline at 1-844-872-2348 (1-844-TRACE-IT) and report it to your local Lands or Natural Resources officer. Be sure to include understandable directions to the location.
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