Hydrilla verticillata, hydrilla

Invasive Species August 16, 2012 Print Friendly and PDF

Invasive Species: Hydrilla verticillata, Hydrilla

Hydrilla is a submersed, rooted invasive aquatic plant that can grow in water to depths of 20 ft. (6.1 m). Plants can survive in depths to 40 ft. (12 m) in nonturbid water. Leaves are whorled in bunches of three to eight, but most often with whorls of five. The midribs of the leaves are reddish, and the undersides have small, raised teeth. Leaves are 0.2-0.8 in. (5-20 mm) long and 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. This species 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 in North America as an aquarium plant in the 1950s. Hydrilla sometimes is confused with Brazilian egeria (Egeria 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, unlike the toothed midrib of hydrilla.

What are invasive species, and why should we be concerned about them? 


Taxonomy: Scientific and Common Names for This Species

Hydrocharitales > Hydrocharitaceae > Hydrilla verticillata (L. f.) Royle

Synonym(s): Florida elodea, water thyme, waterthyme

Hydrilla verticillata - USDA PLANTS Profile

Distribution Maps

Hydrilla - The reported distribution of this invasive species across the United States (Source: Invasive Plant Atlas of the United States)

Up-to-the-minute distribution maps and why they are important 

Reporting This Invasive Species

What is the best way to report the occurrence of an invasive species? 

 How to report an invasive species sighting to EDDMapS - Early Detection & Distribution Mapping System

EDDMapS - Report an invasive species to EDDMapS.

County Extension Offices - Find your local Extension office on this map provided by the USDA.

How to Identify

This invasive species can be identified by looking for the characteristics described in the paragraphs that follow.

Plant

Hydrilla is a submersed, rooted aquatic plant that can grow in water to depths of 20 ft. (6.1 m). Plants can survive in depths to 40 ft. (12 m) in nonturbid water.

Raghavan Charudattan, University of Florida, bugwood.org Leslie J. Mehrhoff, University of Connecticut, bugwood.org

Foliage

Leaves are whorled in bunches of three to eight, but most often with whorls of five. The midribs of the leaves are reddish, and the undersides have small, raised teeth. Leaves are 0.2-0.8 in. (5-20 mm) long and less than 0.1 in. (2 mm) wide and have serrated margins.

Robert Vidéki, Doronicum Kft., bugwood.org Robert Vidéki, Doronicum Kft., bugwood.org

Flower

   
bugwood.org bugwood.org

Fruit and Root Tuber

Steve Hurst, USDA NRCS PLANTS Database, bugwood.org Robert Vidéki, Doronicum Kft.,bugwood.org

Native Species That Resemble Hydrilla

- Images at invasive.org

   
bugwood.org bugwood.org

- Images at invasive.org

   
bugwood.org bugwood.org

Additional Images for Hydrilla

Hydrilla - Images at invasive.org

Learning Resources for Hydrilla

Hydrilla verticillata Identification Card - US Fish and Wildlife Service

Hydrilla verticillata Fact Sheet - US Fish and Wildlife Service

Additional Information, Biology, Control and Management Resources

Control and management recommendations vary according to individual circumstances. Location, habitat, weather, and a variety of other conditions are factors that help determine the best treatment choice. To find the safest and most effective treatment for your situation, consult your state's land-grant institution. If you will use chemicals as part of the control process, always refer to the product label.

United States Land-Grant University System - Find your land-grant university's College of Agriculture, University Cooperative Extension Service, or other related partner on this map provided by USDA.

Fact Sheet - Pennsylvania Department of Conservation and Natural Resources

Plant Invaders of Mid-Atlantic Natural Areas - National Park Service and US Fish and Wildlife Service

Biological Control of Invasive Plants in the Eastern United States - USDA Forest Service

Southeast Exotic Pest Plant Council Invasive Plant Manual - SE-EPPC

Element Stewardship Abstract - The Nature Conservancy

Invasive Plant Atlas of New England - University of Connecticut

Identification and Biology of Non-Native Plants in Florida's Natural Areas - University of Florida

Hydrilla IPM Project - University of Florida

Federal Noxious Weed Disseminules of the United States - USDA Animal and Plant Health Inspection Service (APHIS)

Weed of the Week - USDA Forest Service

Global Invasive Species Database - Invasive Species Specialist Group


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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.