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Home / Aquatic Invasives / Aquatic Plants / Alligatorweed


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Alligatorweed, flower - Photo by Chris Evans; University of Illinois
Scientific Name: 
Alternanthera philoxeroides (Mart.) Griseb. (ITIS)
Achyranthes philoxeroides (ITIS)
Common Name: 
Alligatorweed, alligator weed, pig weed
Native To: 
South America (Spencer and Coulson 1976)
Date of U.S. Introduction: 
First reported in Alabama in 1897 (Masterson 2007)
Means of Introduction: 
Probably introduced through ballast water (Masterson 2007)
Forms dense mats that crowd out native species and impede recreational activities such as boating, swimming, and fishing (Texas Invasives 2007)
Current U.S. Distribution: 
Southeastern U.S., California

Distribution / Maps / Survey Status



Selected Resources

The section below contains highly relevant resources for this species, organized by source. Or, to display all related content view all resources for Alligatorweed.

European and Mediterranean Plant Protection Organization.
IUCN. Species Survival Commission. Invasive Species Specialist Group.
University of Georgia. Center for Invasive Species and Ecosystem Health.
USDA. FS. Institute of Pacific Islands Forestry.

Texas Commission on Environmental Quality, Galveston Bay Estuary Program; Houston Advanced Research Center (HARC).

Federal Government
Smithsonian Institution. Smithsonian Marine Station at Fort Pierce.
Smithsonian Institution. Smithsonian Environmental Research Center. Marine Invasions Research Lab.
DOI. USGS. Wetland and Aquatic Research Center.
Provides distribution maps and collection information (State and County).
USDA. NRCS. National Plant Data Center.

USDA. ARS. National Genetic Resources Program. GRIN-Global.

International Government
New South Wales Department of Primary Industries (Australia).
Australian Government. Department of the Environment and Energy.
Designated Weed of National Significance
Cooperative Research Centre for Australian Weed Management.
State and Local Government
California Department of Food and Agriculture.
See also: Included on California's noxious weed list; see Encycloweedia: Program Details for additional resources
South Carolina Department of Natural Resources. Aquatic Nuisance Species Program.
Texas A&M University. AgriLife Extension Service. Department of Wildlife and Fisheries Sciences.

University of Florida. IFAS. Center for Aquatic and Invasive Plants.