Volunteers Community Partners

Water Lettuce

Water lettuce, Pistia stratoites, cover. Photo by Dr. Bill Haller, University of Florida

Additional Images

Common Name: Water lettuce
Scientific Name: Pistia stratoites
Origin: Africa and South America

Description

Water lettuce is an often free-floating aquatic plant that resembles an open head of lettuce. Feathery roots grow under the plants, which can connect a large number of these plants by stolons. Leaves are light green, thick, softly hairy (pubescent), and have parallel veins and scalloped edges. Water lettuce produces a green berry that turns brown at maturity. Flowers are inconspicuous.

Habitat

The plant can adapt to life in ponds, lakes and quiet areas of rivers and streams, but doesn’t tolerate salt water. While water lettuce is limited by cold winter temperatures, several populations of water lettuce have been observed in New York and Ontario, and they may be successfully reproducing.

Threat

Water lettuce forms thick mats that block sunlight and slow or prevent the growth of native aquatic plants. As the plant dies and decomposes, it removes oxygen from the water, which can disrupt fish communities. Dense mats of water lettuce can hinder swimmers and boaters, prevent other recreational uses of waterways, and restrict water flow in irrigation and flood control canals.

Management

Small and isolated infestations can be easily controlled manually (hand pulling). Larger infestations can be addressed using harvesters, large machines that scoop up plants. Once large infestations have been decreased in size and density using harvesters, hand removal can be used to finish the job. Chemical control is also effective.

Distribution

Early Detection