Alternanthera philoxeroides

alligatorweed, pigweed, alligator weed, pig weed


Leaf Arrangement


Leaf Attachment

petiolate, sessile

Leaf Margin


Leaf Type


Leaf Shape

linear, elliptic, lanceolate, oblanceolate, obovate

Growth Form

forb, emergent aquatic, floating aquatic, aquatic

Flower Color


Flower Month

March - October

Height (meters)

0.3 - 1.0

Milky Sap








Growing Season

Warm season

Wetland Class


Wetland Coefficient of Conservatism


Prairie Coefficient of Conservatism


Field Characters

The stems of alligator weed are hollow and there are small tufts of hair in the axils of the leaves. Opposite leaves with no teeth, pink ring at the nodes and a hollow stem with a few minute vertical lines of whitish hairs on inter-nodes (tiny "mohawks").

Cultural Information

A technique developed by Hardcastle (1958), involves cutting terminal stems about 8 inches long underwater, placing in container of water and soil (without exposing the cut end to air), and swirl the water to settle the soil around the ends. Cuttings were well rooted in 2 weeks (Hardcastle 1958). The roots develop at nodes at least one node should be below the soil. Plants root at the nodes naturally, and these rooted ends can be cut from the plant and potted. Alligator weed is highly resistant to Roundup herbicide but the alligator weed flea beetle (Agasicles hygrophila) has been successfully used to control this species in Louisiana since 1970.

Animal Use

A desirable forage for cattle. The foliage is also eaten by rabbits, deer and nutria.

Natural History

Known in Acadian French as "herbe a cocodrie" or "alligator weed" (Holmes 1990). It is a serious weed of coastal wetlands, and is found throughout Louisiana and Texas where it often clogs waterways. It is not native to the United States and was first reported in the state by R. S. Cocks (1900). Along the gulf coast it is also a pest in gardens that have clay soils or poor drainage.


Aquatic, very wet, or semiterrestrial habitats.

Plant Uses

The stems and leaves are edible when boiled.