Scientific Name Synonyms
alligatorweed, alligator weed, pig weed
- Alternanthera philoxeroides 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.
- Fruits are very small, and single-seeded.
- Ecological Threat
- Alternanthera philoxeroides roots in wet soils or shallow water and grows out into waterways. Alternanthera philoxeroides 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. It is native to South America and was first introduced into the United States around 1900 in ballast water.
- Identification and Biology of Nonnative Plants in Florida’s Natural Areas - Second Edition, by K.A. Langeland, et al. University of Florida-IFAS Pub SP 257. 2008.
- Global Invasive Species Database. 2011. Invasive Species Specialist Group (ISSG) of the IUCN Species Survival Commission
- Virginia Department of Conservation and Recreation
- Invasive Plant Atlas of the MidSouth (IPAMS)
- Clemson University Cooperative Extension
- Texas Invasive Plant and Pest Council
- California Invasive Plant Council
- USDA NRCS PLANTS
- USDA ARS GRIN
Images from Bugwood.org