Hydrilla verticillatas (hydrilla)

Hydrilla verticillata

Photo courtesy California Department of Food and Agriculture

Hydrilla verticillata (hydrilla) is a perennial aquatic plant (family Hydrocharitaceae). It has been observed in the Mojave and Colorado deserts, south and central coasts, San Francisco Bay Area, and Central Valley. Currently, isolated infestations of hydrilla are found in Shasta, Yuba, Lake, Calaveras, Madera, Mariposa, and Imperial counties. Hydrilla forms large mats that fill the water column and can block or severely restrict water flow.

Cal-IPC Inventory rating: High

Cal-IPC Resources on Hydrilla verticillata

• California Invasive Plant Inventory Assessment Form (pdf) - Information gathered by Cal-IPC on the impacts, rate of spread, and distribution of invasive plants in California. Does not include management information.
• Species account from Invasive Plants of California's Wildlands - Includes biology and management information.
• Cal-IPC News - Articles from our quarterly newsletter. Each issue is available as a pdf.List of articles on Hydrilla verticillata.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Hydrilla verticillata.
• Don't Plant a Pest! - Select your region to find non-invasive alternatives to ornamental species. Also see our statewide brochure on trees.

Cal-IPC News Articles

• Blair, C. E. (2009). Invasive aquatic weeds: Implications for mosquito and vector management activities. Cal-IPC Symposium 2009. Visalia, CA, California Invasive Plant Council.
• (1995). Biological control of invasive exotic pest plant species: A report on the importance of maintaining and enhancing our nation's biological control capabilities. CalEPPC News. 3: 6-10.
• Pitcairn, M. (2000). All weeds that have approved biological control agents, accidental introductions and others. CalEPPC News. 8.

Cal-IPC Symposium Proceedings

• DiTomaso, J. M. (1997). Risk analysis of various weed control methods. California Exotic Pest Plant Council Symposium '97. Concord, CA.
• Leavitt, J. R. and C. Pirosko (2002). A brief overview of the California Dept. of Food and Agriculture’s A-rated noxious weed education and eradication program. California Exotic Pest Plant Council Symposium 2002. Sacramento, CA.
• Maly, F. C. (2006). Hydrilla eradication efforts in the Chowchilla River and Eastman Reservoir in Central California: A success story. Cal-IPC Symposium. Rohnert Park, CA.
• O'Connell, R. A. (1997). Hydrilla: A case study: The state of California's noxious weed eradication programs. California Exotic Pest Plant Council Symposium '97. Concord, CA.
• O'Connell, R. A. (1999). The state of California's noxious weed eradication programs. California Exotic Pest Plant Council. Sacramento, CA.
• Tu, M. and J. M. Randall (2003). 2003 Cal-IPC red alert! New invasions, recent expansions, and a few others to be on the look-out For. California Invasive Plant Council Symposium 2003. Kings Beach, CA.

Other Resources on Hydrilla verticillata

• USDA PLANTS database - Federal database with information on identification and distribution, and links to websites in individual states.
• Jepson Online Interchange for California Flora - Information on taxonomy, biology, and distribution from the UC Berkeley Jepson Herbarium.
• CalFlora - Distribution information by county based on submitted observations and herbarium specimens.
• The Nature Conservancy Element Stewardship Abstract - Information compiled by TNC land managers. Photos included for some species.
• Encycloweedia - Plants rated as noxious weeds by the California Department of Food and Agriculture.
• CalPhotos - Images of plants taken mostly in California.
• Natural Resource Projects Inventory - State database with information on resource management projects throughout California. Query by the species of interest.
• California Department of Food and Agriculture - Hydrilla program progress reports

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