Submitted to: Biological Control of Weeds in the United States
Publication Type: Book / Chapter
Publication Acceptance Date: 5/10/2004
Publication Date: 11/1/2002
Citation: Julien, M.H., Center, T.D., Tipping, P.W. 2002. Floating fern (Salvinia). Biological Control of Weeds in the United States. 17-32 (Book Chapter) 2002. Interpretive Summary: Giant salvinia is an exotic floating fern that is native to southeastern Brazil. It is considered a major threat to freshwater ecosystems in the southeastern and western U.S. because it forms thick mats that quickly cover the surface of slow moving bodies of water. These mats disrupt or prevent recreation activities like boating or fishing, block drains, spillways, and intakes for irrigation and electrical generation, provide harborages for disease carrying organisms like mosquitoes and snails, crowd out native aquatic plant species, and reduce the oxygen content of the water which results in degraded fisheries.
Technical Abstract: Giant salvinia, Salvinia molesta is a free-floating perennial aquatic fern adapted to stagnant or slightly flowing fresh water systems in tropical to temperate climates. It was first recorded in the U.S. in 1995 and has since spread to twelve states. There are different growth forms of the plant, namely primary, secondary, and tertiary, exhibit oval leaves ranging from 15 mm wide to 60 mm depending on the growth stage. Leaves are connected with a horizontal rhizome and at each internode there is a pair of above water leaves, a submerged 'root', and associated buds, forming a ramet. Leaf hairs on the abaxial leaf surface are joined together at the tip, forming a diagnostic 'eggbeater' shape. Although it can spread by animals like turtles and alligators or short distances, human activities are responsible for its rapid spread throughout the southeastern and southwestern U. S., particularly by boat trailers which can support viable plant fragments over many miles until putting in a new drainage.