Synonyms: Hottonia serrata, Hydrilla angustifolia, Hydrilla dentata, Hydrilla lithuanica, Hydrilla ovalifolia, Hydrilla wightii, Leptanthes verticillatus, Serpicula verticillata, Vallisneria verticillata, Elodea verticillata
Common names: hydrilla; water thyme; Florida elodea
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 Rating: High
CDFA Rating: A*
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
- Dredging for Hydrilla tubers. Cal-IPC. Vol 23, Issue 3
- Weed biological control agents approved for California. Pitcairn, Michael J.; Smith, Lincoln; Moran, Patrick. Vol 22, Issue 1
- Biological control of invasive exotic pest plant species: A report on the importance of maintaining and enhancing our nation’s biological control capabilities. CalEPPC. Vol 03, Issue 3
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.
- Hydrilla eradication challenges, partnerships and lessons learned. Kratville, David (2016)
- Invasive aquatic weeds: implications for mosquito and vector management activities. Blair, Charles E. (2011)
- Invasive aquatic weeds: Implications for mosquito and vector management activities. Blair, Charles E. (2009)
- Hydrilla eradication efforts in the Chowchilla River and Eastman Reservoir in Central California: A success story. Maly, Florence C. (2006)
- 2003 Cal-IPC red alert! New invasions, recent expansions, and a few others to be on the look-out For…. Tu, Mandy; Randall, John M. (2003)
- Hydrilla: A case study: The state of California’s noxious weed eradication programs. O'Connell, Ross A. (1997)
- Risk analysis of various weed control methods. DiTomaso, Joseph M. (1997)
Other Hydrilla verticillata 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.
- EDDMapS - North American distribution based on Early Detection and Distribution Mapping System.