Myriophyllum spicatum

Myriophyllum spicatum_spike watermilfoil_John Madsen_cropped
Photo: John Madsen

Common names: spike watermilfoil

Myriophyllum spicatum (Eurasian watermilfoil) is a common submersed aquatic perennial (family Haloragaceae). Eurasian watermilfoil can be found in freshwater lakes, ponds, and canals with slow-moving waters in northern and central California, particularly in the San Francisco Bay and San Joaquin Valley regions and Lake Tahoe. This plant grows and spreads rapidly, creating dense mats on the water surface. These monotypic mats out-compete native aquatic plants, reducing species diversity.

Cal-IPC Rating: High

CDFA Rating: C

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.

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 Myriophyllum spicatum 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.
  • USDA PLANTS Database - Federal database with information on identification and distribution, and links to websites in individual states.
  • EDDMapS - North American distribution based on Early Detection and Distribution Mapping System.