Aquatic Plants: Alligator Weed (Alternanthera philoxeroides)

Origin and Date of Introduction: Argentina; 1897.

Pathway / Media: Ballast water.

Reason for Introduction: Accidental, to Mobile, Alabama.

Preferred Habitat: Slow-moving fresh and brackish water.

Ecological / Economic Damage: Degrades habitat and causes navigation difficulties.

Control Options: Manual/mechanical removal; herbicides; biocontrol insects. Alligator weed usually forms sprawling mats in calm waters and along shorelines, but may also be found on land. Here, the invasive plant spreads into a lagoon in Audubon Park, New Orleans, site of the introduction of water hyacinth as an ornamental plant at an 1884 world’s fair.



Photo: Shaun Winterton, Aquarium and Pond Plants of the World, Edition 3, USDA APHIS PPQ, Bugwood.org

Futher Reading: USDA National Invasive Species Information Center