Robert Vidéki, Doronicum Kft.

Giant Salvinia

Salvinia molesta D.S. Mitchell
Floating fern family (Salviniaceae)

Origin: South America

Background
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 Habitat
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 ornamental ponds in Washington, D.C. but was quickly eradicated.

Ecological Threat
Giant salvinia poses a serious threat to lakes, ponds, streams, rivers and other freshwater wetlands, and cultivated rice fields. It 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.

Description and Biology

• Plant: floating aquatic fern with leaves that become compressed into chains in older plants.
• Leaves: about ½-1½ 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.”

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 disposal.

Mic Julien, CSIRO

Troy Evans, Eastern KY Univ.