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Pistia stratiotes

water lettuce

Araceae Pantropical (origin uncertain)

Container Friendly

SunFull Sun – Part Shade

WaterHigh

HardinessZones 9–11

Overview

Pistia stratiotes is a free-floating aquatic that forms a rosette of soft, velvety, light green leaves resembling a small head of lettuce, 4 to 10 inches (10 to 25 cm) across. The leaves are ribbed, wedge-shaped, and covered in soft, water-repellent hairs, with a spongy base that keeps the plant afloat. A dense, feathery mass of roots hangs beneath the rosette into the water. The flowers are tiny and hidden in a small pale spathe at the leaf bases and are rarely noticed. The plant spreads rapidly by short runners that produce new rosettes, forming dense floating mats. It grows in still and slow fresh water across the tropics and warm regions and is frost-sensitive, surviving outdoors only in zones 9 to 11. The mats can cover ponds, block light and oxygen, and clog waterways, and the species is regulated as a noxious weed in many states. It is grown as a seasonal pond plant in colder areas, where winter kills it.

Native Range

The origin is uncertain, likely tropical South America or Africa, and it is now naturalized through fresh waters of the tropics and warm temperate regions worldwide, including the southern United States. It grows in ponds, lakes, ditches, and slow streams.

Suggested Uses

Used as a floating plant in ornamental ponds and aquariums where it is permitted, giving surface shade and taking up nutrients that would otherwise feed algae. Its fast growth and invasive behavior limit outdoor use to contained water features in warm climates. The species is prohibited from release into natural waters in many regions.

How to Identify

Identify it by floating rosettes of soft, ribbed, light green leaves shaped like a small lettuce head, with a trailing mass of feathery roots below. The leaves are covered in velvety, water-repellent hairs. New rosettes form on short runners around the parent. The free-floating habit and lettuce-like rosette are unmistakable among aquatic plants.

Appearance

Size & Dimensions

Height4" - 6"

Width/Spread4" - 10"

Colors

Flower Colors

green

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~12 weeks

Summer Fall

Flowering is inconspicuous and can occur through the warm season. Tiny flowers sit in a small pale green spathe less than 0.5 inch (1.3 cm) long, tucked among the leaf bases. The flowers are rarely seen. The plant reproduces mainly by runners rather than seed.

Detailed Descriptions

Foliage Description

light green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-12 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range6.0 - 7.5(Neutral)

357912

Drainagewet

Water & Climate

Water Needs

High

Frost Tolerance

tender

Time to Maturity

1 season

Care & Maintenance

Care Guide

Float Pistia stratiotes on still or slow-moving fresh water in full sun to part shade. It draws nutrients directly from the water and needs warm temperatures above about 50F (10C). The plant multiplies quickly and can cover a water surface in a single season. It is frost-sensitive and dies when water temperatures fall near freezing. Regular thinning of the rosettes keeps open water and prevents the plant from choking a pond. It is regulated or prohibited in many states, so local rules govern whether it can be grown.

Pruning

Scoop out excess rosettes regularly through the growing season to control the mat. Remove dying or yellowed plants from the water surface. At the end of the season the plants can be composted away from waterways. No structural pruning applies to this floating plant.