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W2O!: Hydrilla
Weeds Watch Out:  Hydrilla


Hydrilla (Hydrilla verticillata )






Hydrilla. Robert Johnson, Cornell University.  Ruthanna Hawkins, Cayuga Lake Watershed Network.  Used with permission.
Hydrilla. Robert Johnson, Cornell University. Ruthanna Hawkins, Cayuga Lake Watershed Network. Used with permission.
Hydrilla Drawing, University of Florida, Center for Aquatic and Invasive Plants Line Drawing DVD Master.  Used with permission.
Hydrilla Drawing, University of Florida, Center for Aquatic and Invasive Plants Line Drawing DVD Master. Used with permission.
  • Native to India/Korea
  • Reported in North America in late 1800s
  • Plant Characteristics
    • Submersed, rooted perennial plant that forms a dense mats from the bottom to the top of the water column (2 inches to 20 feet)
    • Also found as detached floating mats
    • Can grow in deep water up to 20 feet
    • Leaves are lance-shaped in whorls of 4 to 8
    • Leaves are small, sharply toothed with red mid-rib and distinct toothed edges
    • Leaves feel scratchy from spines on the underside of the leaf
    • When pulled from the sediment, tubers might be seen
    • Grows in various depths, nutrient levels and temperatures
    • Commonly spread by plant fragments attached to boating equipment
    • Reproduces by regrowth of stem fragments and by axillary buds (turions)
    • Inhibits swimming, boating, and water recreation
    • Found in springs, lakes, marshes, ditches and rivers
    • Found in the Cayuga Inlet, Fall Creek and the south end of Cayuga Lake


Hydrilla Look Alikes

Invasive Look Alike:  Brazilian Waterweed (
Egeria densa)
  • Invasive plant posing a threat to the Oswego River Basin
  • Plant Characteristics
    • Smooth, while Hydrilla feels harsh, brittle and scratchy
    • Lance shaped leaves arranged in whorls with 4 to 6 leaves per whorl
    • Whorls of leaves typically closer together or denser than those of American elodea
    • Small serrations along the leaf margin are difficult to see with the naked eye
    • Found in both still and flowing waters of lakes, ponds, small streams and ditches

      Egeria, Aquatic Plant Information System (APIS), www.wes.army.mil/el/aqua
      Egeria, Aquatic Plant Information System (APIS), www.wes.army.mil/el/aqua

Native Look Alike:  American Waterweed (Elodea canadensis)
  • Plant Characteristics
    • Submersed perennial that feels smooth, Hydrilla feels harsh, brittle and scratchy
    • Has small lance shaped leaves smaller than a quarter in whorls of three
    • Females have small, white, floating, waxy flowers with three petals
    • Males develop vase-like structure smaller than a dime on thread-like stalks
    • Flowering occurs early to mid-summer
    • Spreads by fragmentation

    • Elodea, Kelly E. Somerlot, Onondaga County CCE 
      Elodea, Kelly E. Somerlot, Onondaga County CCE
Native Look Alike: Southern Naiad (Najas guadalupensis)

  • Plant Characteristics
    • Submersed plant with long stems with many branches
    • Narrow toothed leaves are deep green to purplish green and are no longer than an inch long and less then 1/16 of an inch wide
    • Leaves are in opposite formation and are sometimes in whorls of three
    • Flowers are very small and inconspicuous

    • Southern Naiad, USDA-NRCS PLANTS Database/Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 1: 89.
      Southern Naiad, USDA-NRCS PLANTS Database/Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 1: 89.