Alternanthera philoxeroides

Alternanthera philoxeroides_alligatorweed_JM DiTomaso
Photo courtesy Joseph DiTomaso

Synonyms: Bucholzia philoxeroides Mart., Telanthera philoxeroides (Mart.)

Common names: alligatorweed

Alternanthera philoxeroides (alligatorweed) is a noxious herbaceous aquatic perennial (family Amaranthaceae), that forms dense floating mats. This weed grows in the San Joaquin Valley (Tulare and Kings counties), Los Angeles County, and the Sacramento Delta. It invades lakes, streams, canals, ponds and irrigation ditches. It was previously used in the aquarium trade and is currently rapidly expanding in waterways across California.

Cal-IPC Rating: High

CDFA Rating: A*

Cal-IPC Assessment

Plant Assessment Form - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.

Special Reports

Yolo County Weed Alert by Brenda Grewell, April 2020

Weed Management Notes

  • Management Notes - Information on management techniques and effectiveness from the University of California Cooperative Extension’s Weed Research & Information Center.

Cal-IPC Newsletter Articles

Cal-IPC Symposium Presentations

Presentations are linked where available. Where a presentation is not available, find more information by reading the abstract in the Cal-IPC Symposia Archive.

Other Alternanthera philoxeroides Information

  • CalPhotos - Images of plants taken mostly in California.
  • Calflora - See the distribution of this species on Calflora's map of California.
  • CalWeedMapper - Distribution information with ability to determine regional priorities.
  • Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from UC Berkeley's Jepson Herbarium.
  • CDFA - California official noxious weeds.
  • USDA PLANTS Database - Federal database with information on identification and distribution, and links to websites in individual states.
  • Bugwood - National database from the Center for Invasive Species and Ecosystem Health at the University of Georgia.
  • GBIF - Global distribution information.
  • EDDMapS - North American distribution based on Early Detection and Distribution Mapping System.