Alligatorweed

Alternanthera philoxeroides

Native to South America this weed has spread along the Gulf, Atlantic and Pacific coasts of the United States. It grows in both aquatic and wetland ecosystems. It also is an agriculture weed growing on farmlands. Stem fragments from the plant disperse through waterways.  Nodes generate both roots and stems allowing it to reproduce itself from fragments that consist of as few as a single node.

The plant forms tangled, vine-like mats, that root along shorelines and float in deeper water. Well-established populations of Alligatorweed can develop contiguous mats along the shoreline and can be 30+ feed wide. Aquatic forms of the plant have hollow stems which aids buoyancy; terrestrial forms have denser stems that are not hollow. Oblong leaves grow oppositely in pairs along the stems and are 1.5” to 4" long. Alligatorweed flowers through most of the growing season. White flowers are borne at the nodes; flowers are reminiscent of clover flowers in size, shape and general appearance. 

Fact Sheet: Alligatorweed

Photo credit:  R. Emens, NC Division of Water Resources