Tropical Americas, Asia, Malesia, and Australia
Waterlettuce is a free-floating aquatic perennial that resembles a floating head of lettuce. Plants have feathered roots as well as stolons that produce daughter plants. Leaves are fleshy, wedge-shaped, 1–6 in (2½– 15 cm) long, and covered with dense water repellent hairs. The inflorescence is an inconspicuous spadix with a ring of 6–8 male flowers and one female flower below. They are enclosed by a hairy white spathe. Fruits are very small green berries.
Waterlettuce forms dense mats that displace native species, impede water flow and water navigation, destroy fish spawning habitat, alter water nutrient cycling, reduce production in rice paddies, impede hydroelectricity production, and damage water recreational sectors.
Dray, F.A. and P.T. Madeira. 2022. Waterlettuce (Pistia stratiotes): History and Ecology in North America. In: R.L. Winston, Ed. Biological Control of Weeds in North America. North American Invasive Species Management Association, Milwaukee, WI. NAISMA-BCW-2022-23- WATERLETTUCE-P. https://bugwoodcloud.org/resource/files/23229.pdf