C. Jacono, USGS
Origin: South America
Giant salvinia, also known as water fern or kariba-weed,
was introduced as an ornamental aquatic plant and is
spread to new water bodies on boats and fishing gear, by
dumping of aquaria, and by other unintentional means.
Sale, transport, release and other activities with this
plant are prohibited in the United States by Federal law.
Distribution and Ecological Threat
Giant salvinia has populations scattered throughout the
Southeastern U.S. from eastern Texas through eastern North
Carolina. There are two known occurrences in the tip of
Southern California. In the summer of 2000, a small
population was discovered in aquatic ornamental ponds in
Washington, D.C., and was quickly eradicated. It poses a
serious threat to lakes, ponds, streams, rivers and other
freshwater wetlands, and cultivated rice fields. Giant
salvinia grows rapidly and spreads across water surfaces,
forming dense floating mats that cut off light to other
aquatic plants, reduce oxygen content and degrade water
quality for fish and other aquatic organisms.
C. Jacono, USGS
Description and Biology
Plant: a floating aquatic fern with leaves that become
compressed into chains in older plants.
Leaves: about 1/2 to 11/2 inches long; oval, folded,
and covered with arching hairs that appear like
"beaters" on upper leaf surfaces.
Flowers, fruits and seeds: reproduces and spreads by
tiny spores (rather than flowers).
Spreads: by transport of plant fragments by water,
humans and wildlife.
Look-alikes: Common salvinia (Salvinia minima),
a native plant, looks very similar, but its leaf hairs
do not join at the tip to form "beaters" as
in giant salvinia.
R. Bourke, USGS
Prevention and Control
Do not buy this plant or release it into the wild (these
activities are prohibited by U.S. law). If you think you
see this plant, call 1-877-STOP ANS to report it. If you
have this plant and no longer want it, pile plants onto a
dry sunny surface (e.g., driveway) and let them dry out
completely. Once completely dry, bag them in a sturdy
plastic trash bag and dispose of in a landfill. Contact
proper authorities about other methods of control and
Some aquatic nurseries carry native and non-invasive
alternatives. However, due to the similarity in appearance
among aquatic plants to the untrained eye, they are easily
confused. Contact your state natural resource agency,
native plant society or other resource (see
reference section) for assistance in locating species
appropriate to your location and site conditions.
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