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Aquatic Nuisance Species

Photo of Hydrilla.
Photo credit: C Evans/Univ. of Georgia,

Scientists believe Hydrilla (Hydrilla verticillata) is the worst established aquatic weed in many places. Plants form large, dense populations that displace native plants such as pondweeds (Potamogeton spp.) and eelgrass (Vallisneria americana) and impair water use.

Hydrilla is quite prolific and spreads by four different methods:

  1. Fragmentation: Fragments attached to boat motors are spread from lake to lake and regrow into entire plants. Fragments are also spread by draglines, bait buckets, and boat trailers.
  2. Tubers: Potato-like fleshy outgrowths of the root or shoot, called tubers, are dispersed by water.
  3. Turions: One turion (a compact bud) can produce 6,000 new turions per square meter, and each one of these can grow into a new plant. Turions can survive several days out of the water (1).
  4. Seeds: The seed-holding capsules are sometimes spiny and probably dispersed by animals as well as by water (2).


  1. University of Florida, Center for Aquatic and Invasive Plants. <http://aquat1.ifas.ufl.edu/hydcirc.html>.
    Accessed 2006 Sept 19.
  2. Aquatic Nuisance Species Task Force. <http://www.anstaskforce.gov/spoc/hydrilla.php>.
    Accessed 2006 Aug 27.