Water lettuce (Pistia stratiotes) is a free-floating aquatic invasive species. The native range of this species is unknown, but it can be found in local lakes, rivers, streams, and ponds. Growers are currently allowed to sell this species in Michigan, but they can easily escape cultivation due to human transportation or releasing them.
The free-floating plants resemble an open head of lettuce that you would buy from the store. The leaves are thick, tough, rounded at the ends and are light green in color. The roots dangle below the plants when pulled from the water. The flowers are small and yellow to green in color. The entire plant rosette is roughly 4 inches wide and 2 inches tall.
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Environmental effects
Large infestations of this plant will block out sunlight to native plants below the surface. This can decrease their productivity and decrease native plant diversity. There may also be a decrease in algae present which is a source of food for many fish species. The floating mats are also the perfect place for mosquitos to breed and lay their eggs. Boat travel may be impacted when there is a large floating mat present.
Treatments
Prevention is the best treatment method. Do not release cultivated water lettuce into any body of water.
NON-CHEMICAL CONTROL METHODS
- Hand pulling: this species can be hand pulled from the surface of the water. It is important to not leave any remains near or in water, otherwise the species will regrow.
CHEMICAL CONTROL METHODS
- Foliar spraying: be sure to select an herbicide that is aquatic safe and check to see what permits are needed before treatment can be carried out.