It has recently been found to absorb a variety of toxins and heavy metals and has come into use for water purification. See Also Floating Water Hyacinth Water Lettuce Pistis stratiotes Water Lettuce is also called Water Bonnet. The leaves of Water Lettuce are 4 to 8 inches in length and have a velvety surface thanks to very small, hair-like structures covering the leaf surface. Leaves generally have a smooth edge and form rosettes resembling a head of lettuce. Leaves have approximately 10 distinct veins radiating outward from the narrowed leaf base and are spongy to facilitate buoyancy.
Roots dangle below and are feather-like, but unbranched.
Flowers are very small and in the center of the rosette. Water Lettuce floats on quiet ponds, lakes and bayous. It prefers soft, acid waters and is cold sensitive. It is occasionally sold in the pet trade. Water Lettuce can completely cocver ponds, bays and small lakes blocking access and shading out more desirable aquatic plant species.