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

Texas Invasives Database - Alternanthera philoxeroides

Invasive Species Compendium - Alternanthera philoxeroides
CAB International.

Alternanthera philoxeroides (Amaranthaceae)
European and Mediterranean Plant Protection Organization.

Global Invasive Species Database - Alternanthera philoxeroides (aquatic plant, herb)
World Conservation Union. Invasive Species Specialist Group.


Alternanthera philoxeroides (Mart.) Griseb. (Alligatorweed) - Aquatic Plant Information System (APIS)
DOD. USACE. Engineer Research and Development Center. Environmental Laboratory.

Germplasm Resources Information Network (GRIN) - Alternanthera philoxeroides
USDA. ARS. National Genetic Resources Program.

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

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

Fact Sheet: Alligator weed (Dec 2013; PDF | 2.53 MB)
Biosecurity Queensland (Australia).

Alligator Weed - Weed Management Guide (2003; PDF | 353 KB)
Cooperative Research Centre for Australian Weed Management.
See also: Alligator Weed Strategic Plan 2012-2017 (PDF | 1.02 MB)

Alternanthera philoxeroides - Weeds in Australia
Department of the Environment, Water, Heritage and the Arts (Australia).

Weed Profile: Alligator weed
New South Wales Department of Primary Industries (Australia).


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

South Carolina Department of Natural Resources. Aquatic Nuisance Species Program.

Alligator Weed
South Carolina Department of Natural Resources. Freshwater Fisheries Section.


Weed Control in Natural Areas in the Western United States: Alligatorweed (2013; PDF | 196 KB)
University of California. Weed Research and Information Center.

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

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

Alligator Weed
Mississippi State University Extension Service; Mississippi Agricultural and Forestry Experiment Station.

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


Alligatorweed, pig weed
Guide to Invasive Plants of the Galveston Bay Area.


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: Jan 21, 2016
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