Exotics Plant Species Report
Giant Salvinia Invasion
December, 1999

Giant salvinia (Salvinia molesta) is an aquatic fern from South America prohibited in the United States by Federal law. Its introduction by humans has caused severe economic and ecological problems in many countries including New Zealand, Australia, and South Africa. It is currently growing in the Colorado River in Imperial County and was being sold in nurseries in San Diego County. Giant salvinia grows rapidly to cover the surface of lakes and streams, spreading aggressively by vegetative fragments. It forms floating mats that shade and crowd out native plants. Its thick mats reduce oxygen content and degrade water quality for fish and other aquatic organisms. Mats impede boating, fishing, and swimming, and clog water intakes for irrigation and electrical generation. Giant salvinia has oblong floating leaves 1/2 to 1 1/2 inches long. As plants mature and aggregate into mats, leaves are folded and compressed into upright chains. The leaf surfaces have rows of cylindrical hairs topped with four branches that are joined at the tips to form a cage that can be viewed with a hand lens. If you see this plant being offered for sale in a nursery, please let the management of the nursery know they are selling a federally listed noxious weed and inform the County Agriculture Commissioner. If you come upon giant salvinia in a pond or river in the county, please inform Bill Winan with the San Diego County of Agriculture.

-- Cindy Burrascano

More information and photos of Giant Salvinia can be found on the Wildland Weeds Management & Research Program pages of The Nature Conservancy

Other Resources:
CNPS Invasive Exotics (state site)
CNPS Policy on Invasive Exotics
California Exotic Pest Plant Council