alligatorweed USDA PLANTS Symbol: ALPH
U.S. Nativity: Exotic
Habit: Aquatic Forbs/Herbs
Alternanthera philoxeroides (Mart.) Griseb.

Jump to: Resources | Images | Distribution Maps | Sources
Taxonomic Rank: Magnoliopsida: Caryophyllales: Amaranthaceae
Synonym(s): alligator weed, pig weed
Native Range: So. Amer. (GRIN);

Alligatorweed is an emergent or rooted floating plant that invades aquatic areas and adjoining uplands throughout the southern portions of the United States. Plants have hollow stems and can grow to 3 ft. (1 m) tall. Opposite, elliptical leaves are thick but non-succulent and are up to 4 in. (10 cm) long. Flowering occurs during the summer with white, clover-like heads in the axils of the leaves. Alligatorweed roots in wet soils or shallow water and grows out into waterways. Alligatorweed can also grow terrestrially, forming smaller, tougher leaves. The thick mats can displace native vegetation and wildlife habitat, clog waterways, restrict oxygen levels of water, increase sedimentation, interfere with irrigation and prevent drainage. Alligatorweed is native to South America and was first introduced into the United States around 1900 in ballast water.

Identification, Biology, Control and Management Resources

Selected Images from Invasive.orgView All Images at Invasive.org


Flower(s);
Robert H. Mohlenbrock, USDA NRCS PLANTS Database, Bugwood.org
Additional Resolutions & Image Usage

Flower(s); the white flowers are arranged in stalked, short, headlike spikes, and have a style
Gary Buckingham, USDA Agricultural Research Service, Bugwood.org
Additional Resolutions & Image Usage

Foliage; Opposite leaves
Rebekah D. Wallace, University of Georgia, Bugwood.org
Additional Resolutions & Image Usage

Plant(s);
James H. Miller, USDA Forest Service, Bugwood.org
Additional Resolutions & Image Usage

Foliage;
Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); in flower
Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
Additional Resolutions & Image Usage

Fruit(s); Fruit with attached perianth. Similar to an FNW taxon.
Julia Scher, USDA APHIS PPQ, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
Additional Resolutions & Image Usage

Infestation;
Chris Evans, Illinois Wildlife Action Plan, Bugwood.org
Additional Resolutions & Image Usage

Plant(s); USDA NRCS. Wetland flora: Field office illustrated guide to plant species. USDA Natural Resources Conservation Service.
USDA PLANTS Database, 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
 


State(s) Where Reported invasive.
Based on state level agency and organization lists of invasive plants from WeedUS database.

U.S. National Parks where reported invasive:
Colonial National Historical Park (Virginia)



Invasive Listing Sources:
Alabama Invasive Plant Council
California Invasive Plant Council
Eric Ulaszek, U.S. Forest Service, Midewin National Tallgrass Prairie, Illinois
Faith Campbell, 1998
Florida Exotic Pest Plant Council
Georgia Exotic Pest Plant Council
Gulf of Mexico Regional Panel, Aquatic Nuisance Species Annual Report, 2001
Jil M. Swearingen, Survey of invasive plants occurring on National Park Service lands, 2000-2007
John Randall, The Nature Conservancy, Survey of TNC Preserves, 1995.
Mid-Atlantic Exotic Pest Plant Council, 2005
North Carolina Division of Parks and Recreation, Department of Environment and Natural Resources, 1998
Tennessee Exotic Pest Plant Council
Virginia Department of Conservation and Recreation, 2009