Ludwigia hexapetala (Uruguay water-primrose)

Ludwigia hexapetala

Photo courtesy Joseph DiTomaso

Ludwigia hexapetala (Uruguay water-primrose) is an aquatic plant (family Onagraceae) that forms dense mats in waterways, reaching above and below the water surface. This dense growth impedes water movement, blocks the growth of native plants, and reduces available habitat for waterbirds and fish. Although this species has been naturalized in California for at least 25 years, it has grown exponentially in the past several years, leading to increased concern over its impacts on waterways. Pieces of Uruguay water-primrose mats can catch on boat and other watercraft that then spread plants to new areas.

Cal-IPC Inventory rating: High - Alert

Cal-IPC Resources on Ludwigia hexapetala

• 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.
• Cal-IPC News - Articles from our quarterly newsletter. Each issue is available as a pdf. List of articles on Ludwigia hexapetala.
• Cal-IPC Symposium Proceedings - Presentations and papers from our annual Symposium. List of articles on Ludwigia hexapetala.
• Don't Plant a Pest! - See our statewide brochure on aquatic plants.

Cal-IPC News Articles

• Meisler, J. (2009). Lessons from Ludwigia control in Sonoma County. Cal-IPC News. 17: 4,5,12.
• Burkhart, B. and M. Kelly (2005). Which weeds dominate southern California urban riparian systems? Cal-IPC News. 13: 4-5,12.
• Charles E Blair, M. (2006). Invasive aquatic weeds: Implications for mosquito and vector management activities. Cal-IPC Symposium, Rohnert Park, CA, California Invasive Plant Council.
• McNabb, T. J. and J. Meisler (2006). Two years of Ludwigia control in the Laguna de Santa Rosa – process and progress. Cal-IPC Symposium, Rohnert Park, CA, California Invasive Plant Council.
• Verdone, L. (2004). Creeping water primrose (Ludwigia hexapetala): the ecology and impacts of an invasive aquatic plant the Laguna de Santa Rosa. Cal-IPC.

Cal-IPC Symposium Proceedings

• Blair M.D., C. E. (2006). Invasive aquatic weeds: Implications for mosquito and vector management activities. Cal-IPC Symposium. Rohnert Park, CA.
• McNabb, T. J. and J. Meisler (2006). Two years of Ludwigia control in the Laguna de Santa Rosa process and progress. Cal-IPC Symposium. Rohnert Park, CA.
• Meisler, J. A. (2005). Control of water primrose (Ludwigia hexapetala) in a freshwater wetland. California Invasive Plant Council Symposium 2005. Chico, CA.
• Verdone, L. (2003). Creeping water primrose (Ludwigia hexapetala) in the Laguna de Santa Rosa. California Invasive Plant Council Symposium 2003. Kings Beach, California, CA.
• Verdone, L. (2004). Creeping water primrose (Ludwigia hexapetala): The ecology and impacts of an invasive aquatic plant in the Laguna de Santa Rosa. California Invasive Plant Council Symposium 2004. Ventura, CA.

Other Resources on Ludwigia hexapetala

• 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 Management Summary - Information compiled by TNC land managers. Photos included for some species.
• CalPhotos - Images of plants taken mostly in California.

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