559 Pistia stratiotesCommon Names: water-lettuce, shell-flower Family: Araceae (arum Family)
Waterlettuce is a floating water plant with 6 in (15 cm) rosettes of ribbed, Ruffles® Potato Chip-like leaves. The rosettes are connected by stolons that break easily. The leaves are fleshy-thick, pale green and velvety-hairy, which causes water to bead and keeps them from getting wet. The feathery roots are white, purple and black, and quite showy, hanging down a foot or so below the floating rosettes. Waterlettuce frequently forms solid mats on the water's surface and can become a serious pest.
Waterlettuce thrives in still waters in swamps, ponds, lakes, and sluggish rivers in the tropics and subtropics in both the Old and New Worlds. In the United States it is restricted to Peninsular Florida where it probably was introduced.
CultureLight: Waterlettuce needs full sunlight or slightly filtered sunlight. Moisture: Waterlettuce typically floats on the surface, but can withstand periods of drawdown as long as the mud does not dry out completely. Hardiness: USDA Zones 10 - 11. Occasional in northern Florida, Zone 9. Propagation: Waterlettuce propagates vegetatively by growing stolons (stemlike shoots) which produce new rosettes. Seeds are produced in the tropics and these are said to be easy to germinate. Waterlettuce apparently does not flower in Florida, perhaps because an essential pollinator is not present.
Waterlettuce is difficult to maintain in artificial conditions. It can be grown in tropical or heated aquaria with a glass cover and full sunlight, or in a greenhouse pool. The air must be at least 75º (24ºC) degrees and permanently humid above the water. Waterlettuce can be grown in a temperate water garden, but must be lifted before frost and overwintered on damp sand or peat at no colder than 50 º (10ºC).
The arum family contains about 1500 species, including skunk cabbage, jack-in-the-pulpit, golden club (Orontium aquaticum), and calla lily. These are monocots, members of the monocotyledones, one of the two primary groups of flowering plants, or angiosperms. The other group is the dicotyledones. Monocots are distinguished from dicots by having one instead of two embryonic seed leaves or cotyledons (these are the first leaves you see when a seed germinates); parallel-veined instead of net-veined leaves; always lacking cambium and therefore true woody tissue; and flower parts typically in sets of three. Familiar monocots are the grasses, sedges, bananas, bromeliads, lilies, irises, orchids, and palms. There are many more species of dicots than of monocots.
Waterlettuce is on the Florida Department of Environmental Protection's list of Prohibited Species, and as such it is unlawful to possess or transport this plant in Florida.
Steve Christman 07/12/99; updated 8/27/03, 9/7/04