hydrilla

Hydrocharitales > Hydrocharitaceae > Hydrilla verticillata (L. f.) Royle
Synonym(s): Florida elodea, water thyme, waterthyme

Hydrilla is a submersed, rooted aquatic plant that can grow in water up to depths of 20 ft. (6.1 m). Plants can survive in depths up to 40 ft. (12 m) in non-turbid water. Leaves are whorled in bunches of 3-8, but most often with whorls of 5. The midribs of the leaves are reddish in color with the undersides having small, raised teeth. Leaves are 0.2-0.8 in. (5-20 mm) long, less than 0.1 in. (2 mm) wide and have serrated margins. Hydrilla forms dense mats at the surface of the water. The dense mats can restrict native vegetation, irrigation practices, recreation, hydroelectric production, and water flow. It can invade most slow-moving or still water systems. Hydrilla is believed to be native to Asia or Africa, although it is widely spread across the globe. It was first introduced into North America as an aquarium plant in the 1950s. Hydrilla can sometimes be confused with Brazilian egeria (Ergeria densa Planch.) and Canadian waterweed (Elodea canadensis Michx.). The leaves of Canadian waterweed occur in whorls of three along the stem and are up to 0.2 in. (5 mm) wide. The midrib of Brazilian egeria is smooth as opposed to the toothed midrib of hydrilla.


Identification, Biology, Control and Management Resources

  • Weeds of the Week - USDA Forest Service, Northeastern Area, Forest Health Protection

Selected Images from Invasive.org

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Feature(s); tubers
Tim Murphy, University of Georgia, Bugwood.org
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Plant(s); Whole plants out of water
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Plant(s);
Chris Evans, River to River CWMA, Bugwood.org
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Plant(s);
Chris Evans, River to River CWMA, Bugwood.org
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Plant(s);
David J. Moorhead, University of Georgia, Bugwood.org
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Infestation;
Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
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Infestation;
Michael Frank, Galileo Group Inc., Bugwood.org
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Infestation;
James R. Allison, Georgia Department of Natural Resources, Bugwood.org
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Infestation;
David J. Moorhead, University of Georgia, Bugwood.org
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Dispersal; tangled on boat motor
Wilfredo Robles, Mississippi State University, Bugwood.org
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Seed(s);
Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org
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Invasive Reference(s):

Check Invasive.org for most current lists.
  • Federal Noxious Weed List
  • Alabama - IPC List
  • Arizona - Noxious Weed Law
  • California - Noxious Weed Law
  • California - Invasive Plant Inventory
  • Colorado - Noxious Weed Law
  • Connecticut - Noxious Weed Law
  • Florida - EPPC list
  • Georgia - EPPC list
  • Maine - Noxious Weed Law
  • Massachusetts - Noxious Weed Law
  • Mississippi - Noxious Weed Law
  • New Mexico - Noxious Weed Law
  • Nevada - Noxious Weed Law
  • North Carolina - Noxious Weed Law
  • Oregon - Noxious Weed Law
  • Rhode Island - Noxious Weed Law
  • South Carolina - Noxious Weed Law
  • Tennessee - EPPC List
  • Texas - Noxious Weed Law
  • Texas - Invasive Plant List
  • Vermont - Noxious Weed Law
  • Virginia - Invasive Alien Plant Species
  • Washington - Noxious Weed Law
  • Mid-Atlantic - EPPC List
  • Invasive Plants: Western North America
  • Invasive Plants: Guide to Identification and the Impacts and Control of Common North American Species
  • Invasive Plants of the Upper Midwest
  • Invasive Plant Atlas of New England
  • Invasive Plant Atlas of the Mid-South


External Links


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USDA Forest Service Bugwood University of Georgia