Native to: Brazil
Considered in of the top most invasive aquatic plants worldwide, Giant salvinia readily colonizes disturbed habitats including rice paddies, flood canals, artificial lakes and hydro-electric facilities as well as natural waterways such as swamps, lakes, and rivers. It has been transported around the world as an ornamental for water gardens. In Florida it has been detected in 7 counties in Florida and because it is not widespread it is a top priority for immediate eradication whenever found in hopes of keeping it from becoming a more widespread and costly problem. If you see this plant in cultivation or in the wild, please contact the Florida Fish and Wildlife Conservation Commission at 850-617-9430.
Habit: free-floating aquatic fern. stems rootless(although dangling 3rd leaf resembles roots), hairy, about 10 cm long. Exhibits great variation in form and structure depending on habitat conditions such as space and nutrient availability.
Leaves: oblong floating leaves, 1/2 to 1 1/2 inches long. Young plants have smaller leaves that lie flat on the water surface. As plants mature and aggregate into mats, leaves are folded and compressed into upright chains. Leaf surfaces have rows of cylindrical hairs topped with four branches that are joined at the tips to form a "cage". These hairs give a velvety appearance and repel water.
Spores: underwater root-like structures conceal stalks with egg-shaped spore cases.
Distribution in Florida: limited occurrences in 7 counties.
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 important native plants. 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.
Thoroughly clean boats, equipment, and gear upon leaving water bodies. Report suspected observations to FWC immediately.
When populations are small, manual removal can be effective. Where possible, water level manipulation may be employed as well.
Mechanical harvesting is most effective on early stage, localized populations or as a part of a larger integrated pest management strategy as it is often cost prohibitive.
The salvinia weevil (Cyrtobagous salviniae), native to South America, is widespread in Florida. It feeds and reproduces only on plants in the Salviniaceae family.
Herbicides can provide effective short and/or long-term control depending on the choice of product and the method and frequency of application. Of the herbicides currently registered by the US Environmental Protection Agency for use in aquatic sites, ten provide good (> 75%) to excellent (> 90%) control of common salvinia. The most widely used herbicides include diquat, glyphosate, flumioxazin and carfentrazone-ethyl. It is important to consult an expert for assistance in developing the most effective and integrated approach to management.