| hydrilla | USDA PLANTS Symbol: HYVE3 U.S. Nativity: Exotic Habit: Aquatic Forbs/Herbs |
| Hydrilla verticillata (L. f.) Royle |
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Taxonomic Rank: Liliopsida: Hydrocharitales: Hydrocharitaceae |
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| Synonym(s): Florida elodea, water thyme, waterthyme | |
| Native Range: Europe; Old World (BAIL); | |
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. |
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Identification, Biology, Control and Management Resources
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| Selected Images from Invasive.org | View All Images at Invasive.org |
 Plant(s); USDA APHIS PPQ Archive, USDA APHIS PPQ, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Discovered in the Crystal River in south Florida in 1960. Raghavan Charudattan, University of Florida, Bugwood.org Additional Resolutions & Image Usage |
 Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage |
 Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage |
 Foliage; Robert Vidéki, Doronicum Kft., Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); Leslie J. Mehrhoff, University of Connecticut, Bugwood.org Additional Resolutions & Image Usage |
 Plant(s); David J. Moorhead, University of Georgia, Bugwood.org Additional Resolutions & Image Usage |
 Seed(s); Steve Hurst, USDA NRCS PLANTS Database, Bugwood.org Additional Resolutions & Image Usage |
| EDDMapS Distribution: This map is incomplete and is based only on current site and county level reports made by experts and records obtained from USDA Plants Database. For more information, visit www.eddmaps.org Alternative content
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 State(s) Where Reported invasive. Based on state level agency and organization lists of invasive plants from WeedUS database. Alternative content
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| U.S. National Parks where reported invasive: |
| Colonial National Historical Park (Virginia) George Washington Memorial Parkway (Virginia) National Capital Parks East (Washington, D.C.) |
