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You are here: Home / Aquatic Species / Species Profiles / Alligatorweed
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Alligatorweed - Invasive.org

Scientific name: Alternanthera philoxeroides (Mart.) Griseb. (ITIS)

Synonym: Achyranthes philoxeroides (ITIS)

Common names: Alligatorweed, alligator weed, pig weed

Click image to enlarge

Selected Resources

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)

Impact: 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



Selected Resources:


Pacific Island Ecosystems at Risk (PIER) - Alternanthera philoxeroides
USDA. FS. Institute of Pacific Islands Forestry.

Invasive Plant Atlas of the MidSouth - Alligatorweed
Mississippi State University. Geosystems Research Institute.

Invasive Plant Atlas of the United States - Alligatorweed
University of Georgia. Center for Invasive Species and Ecosystem Health.

Texas Invasives Database - Alternanthera philoxeroides

The Quiet Invasion: A Guide to Invasive Species of the Galveston Bay Area - Alligatorweed, pig weed
Texas Commission on Environmental Quality, Galveston Bay Estuary Program; Houston Advanced Research Center (HARC).

Invasive Species Compendium - Alternanthera philoxeroides
CAB International.

Plantwise Technical Factsheet - Alligator Weed (Alternanthera philoxeroides)
CABI. Plantwise Knowledge Bank.

EPPO Global Database - Alternanthera philoxeroides
European and Mediterranean Plant Protection Organization.

Global Invasive Species Database - Alternanthera philoxeroides (aquatic plant, herb)
IUCN. Species Survival Commission. Invasive Species Specialist Group.

Federal Government

Nonindigenous Aquatic Species Database: Fact Sheet - Alligatorweed
DOI. USGS. Wetland and Aquatic Research Center.
Provides distribution maps and collection information (State and County).

U.S. National Plant Germplasm System - Alternanthera philoxeroides
USDA. ARS. National Genetic Resources Program. GRIN-Global.

PLANTS Database - Alligatorweed
USDA. NRCS. National Plant Data Center.

Indian River Lagoon Species Inventory - Alternanthera philoxeroides
Smithsonian Institution. Smithsonian Marine Station at Fort Pierce.

National Exotic Marine and Estuarine Species Information System (NEMESIS): Chesapeake Bay Introduced Species Database - Alternanthera philoxeroides
Smithsonian Institution. Smithsonian Environmental Research Center. Marine Invasions Research Lab.

International Government

Weeds in Australia - Alligator Weed (Alternanthera philoxeroides)
Australian Government. Department of the Environment and Energy.
Designated Weed of National Significance

Invasive Plants: Restricted Invasive Plants - Alligator Weed
Queensland Business and Industry Portal (Australia).

Weeds of National Significance: Weed Management Guide - Alligator Weed (2003)
Cooperative Research Centre for Australian Weed Management.

NSW WeedWise: Alligator Weed
New South Wales Department of Primary Industries (Australia).

State Government

Encycloweedia: Data Sheet - Alligatorweed
California Department of Food and Agriculture.
See also: Included on California's noxious weed list; see Encycloweedia: Program Details for additional resources

Illegal Aquatic Plants - Alligatorweed
South Carolina Department of Natural Resources. Aquatic Nuisance Species Program.


Plant Profile: Alternanthera philoxeroides
University of Florida. IFAS. Center for Aquatic and Invasive Plants.

AQUAPLANT - Alligator Weed
Texas A&M University. AgriLife Extension Service. Department of Wildlife and Fisheries Sciences.


Integrated Taxonomic Information System. Alternanthera philoxeroides. [Accessed Sep 10, 2014].

Masterson, J. 2007. Alternanthera philoxeroides. In: Indian River Lagoon Species Inventory. Smithsonian Marine Station.

Spencer, N.R. and J.R. Coulson. 1976. The biological control of alligatorweed, Alternanthera philoxeroides, in the Unites States of America. Aquatic Botany 2:177-190.

Texas Invasives Database. 2007. Alternanthera philoxeroides.

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Last Modified: Jul 21, 2018
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