Alternanthera philoxeroides
Common Name(s): Alligator weed
Non-Native to Florida
Origin: South America 1
Introduction to Florida: 1894 (accidental: ballast) 2
This species appears on the following legally prohibited plant lists
| Federal Noxious Weed List | Florida Noxious Weed List | Florida Prohibited Aquatic Plants List |
| No | No | Yes |
UF-IFAS Assessment of Non-Native Plants in Florida’s Natural Areas
CATEGORY II on the Florida Exotic Pest Plant Council’s (FLEPPC) 2017 List of Invasive Plant Species
Download a recognition card (PDF) from Invasive and Non-native Plants You Should Know3
Download a page (PDF) from Identification and Biology of Nonnative Plants in Florida’s Natural Areas – Second Edition1
See Table 1 in Florida’s Established Arthropod Weed Biological Control Agents and Their Targets (2013) for a list of arthropod biological control agents that occur on this species.
For brief control information, see Efficacy of Herbicide Active Ingredients Against Aquatic Weeds (EDIS Pub #SS-AGR-44)
Video Transcript
Alligator weed – Alternanthera philoxeroides
Alligator weed is not native to Florida.
Alligator weed can grow in a variety of habitats, although it is usually found in water. Sometimes it forms sprawling mats over deep rivers, or along shorelines. Sometimes it is a pest on land. Alligator weed is an herb that occurs throughout Florida and flowers in the warm months. It has smooth stems that trail along the ground or out across the water. The stems are hollow. They have nodes from which other stems and roots grow. The simple leaves of alligator weed are elliptic and have smooth margins. The leaves are opposite, which means that two leaves grow on opposite sides of the stem, at the same place on the stem. The distinctive white flowers can be easily recognized. What appears to be one flower is actually a cluster of several flowers. They are whitish and papery looking and feeling. The flower cluster grows on a stalk that can be 2 inches long.
- Alligator weed has
- whitish, papery flowers on stalks,
- sprawling stems that are hollow, and
- leaves that are opposite on the stem.
Biological control insects of alligator weed
- Alligatorweed flea beetle Agasicles hygrophila Selman and Vogt (Coleoptera: Chrysomelidae: Halticinae) by Ted D. Center, James P. Cuda, Michael J. Grodowitz EENY 462 (2012)
- Alligatorweed thrips (suggested) Amynothrips andersoni ONeill (Insecta:Thysanoptera:Phlaeothripidae) by Ted D. Center, James P. Cuda, and Michael J. Grodowitz. EENY 476/IN 859 (2013)
View the herbarium specimen image from the
University of Florida Herbarium Digital Imaging Projects.
Citations
1. Identification and Biology of Nonnative Plants in Florida’s Natural Areas – Second Edition, by K.A. Langeland, H.M. Cherry, et al. University of Florida-IFAS Publication # SP 257. 2008.
2. Strangers in Paradise, Impact and Management of Nonindigenous Species in Florida, Chapter 2: Florida’s Invasion by Nonindigenous Plants: History, Screening, and Regulation, by D.R. Gordon and K.P. Thomas, pp. 21-37. Island Press, Washington, DC, 1997.
3. Invasive and Non-native Plants You Should Know – Recognition Cards, by A. Richard and V. Ramey. University of Florida-IFAS Publication # SP 431. 2007.