Gardening Plants & Flowers Perennials

How to Grow and Care for Water Lettuce

Where invasive, this aquatic plant can clog waterways and hurt water quality

Water lettuce plant with bright green fuzzy rosettes floating in pond

The Spruce / Adrienne Legault

Water lettuce, or water cabbage, is a floating non-edible pond plant with fuzzy rosettes of leaves resembling heads of lettuce. Each leaf has deep ribs, parallel veins, scalloped edges, and no significant stems. Water lettuce produces small, insignificant white or pale green flowers hidden in the foliage, blooming from late summer to late fall. Water lettuce grows best in freshwater conditions and requires 11 to 12 hours of full sunlight (or dappled light in high heat). It is toxic if consumed by humans and pets.

Common Name Water lettuce, water cabbage, Nile cabbage
Botanical Name Pistia stratiotes
Plant Type Perennial
Mature Size 6 in. tall, 10 in. wide
Sun Exposure Full, partial
Water pH Neutral
Bloom Time Summer, fall
Flower Color Green, white
Hardiness Zones 8-10 (USDA)
Native Area Africa
Toxicity Toxic to people and pets

Water Lettuce Benefits

Water lettuce is great for cleaning pond water of decomposition byproducts and is often used to keep the water healthy for fish and aquatic life. This plant also reduces algae blooms by blocking sunlight in the water and using the nutrients needed for the algae to bloom.

It can be grown in water gardens providing shelter for small fish, but larger fish, such as koi, cichlids, and goldfish, may nibble on and damage the plants. 

Although cows won't eat it, it can be used for pig feed.

Warning

Water lettuce originated in Africa in the Nile River but has spread worldwide in aquatic gardens and ponds. If not contained, this plant can be invasive outside of its native area and can kill native vegetation and fish by choking out sunlight and air exchange on the water’s surface.

Where it is hardy, water lettuce can clog irrigation or drainage systems and is prohibited in Florida, Louisiana, Mississippi, Texas, and New Zealand.

Water Lettuce Care

Here are the main care requirements for growing water lettuce:

  • Use in water gardens, ponds, or containers both indoors and outdoors.
  • Needs full to partial sunlight, depending on the heat and exposure level; too much sun can burn its leaves or cause yellowing.
  • Give a neutral to a slightly alkaline or slightly acidic water environment, and ensure it's not salty or has a noticeable lime content.
  • Thrives in water that is 70 to 80 degrees Fahrenheit.
Water lettuce plants with bright fuzzy rosettes floating in pond from above

The Spruce / Adrienne Legault

Water lettuce plants with fuzzy rosettes on pond water closeup

The Spruce / Adrienne Legault

Water lettuce plant with fuzzy rosette leaves closeup

The Spruce / Adrienne Legault

Light

Water lettuce needs full to partial sun exposure. Afternoon shade will help protect it from intense heat. Water lettuce grown in nurseries is often raised in lower light conditions. So, give new plants time to adjust by placing them in low lighting and slowly increasing exposure to more sunlight as the plants become established. 

Too much sunlight may cause yellowing leaves. By contrast, plants that receive less-than-ideal sun exposure may have leaves darker green than is typical.

Soil

The roots of this plant are free-floating, so soil is not necessary for healthy growth.

Water

Water conditions are essential to growing water lettuce, as it is an aquatic, floating plant. Soft to moderately hard water is best. Water lettuce is sensitive to water minerals and can handle no more than 2.5 ppt of salt. It cannot tolerate lime.

Similar to considering soil pH for potted or garden plants, you should also consider the pH of water for the health of water lettuce. This plant prefers pH levels that are neutral or slightly alkaline, or slightly acidic. Aim for a water pH of 6.5 to 7.5.

Temperature and Humidity

Water lettuce does best in water temperatures between 70 and 80 degrees Fahrenheit. It's perennial in USDA zones 9 to 11 and grown as an annual outside its hardiness range.

Because this plant lives in water, it thrives in medium to high humidity levels. Low humidity levels will challenge growing this plant as it can dry out the leaves.

Fertilizer

If water lettuce leaves begin to turn yellow, a lack of nutrients may be a possible cause. If the water lacks the right levels of nutrients, you may need to supplement it with a fertilizer treatment.

There are several different ways to fertilize water lettuce. You can remove the plants and let them sit for a few hours in a tub of liquid fertilizer, add fertilizer straight to the pond or aquarium, or add a nutrient booster to the water. 

If you add fertilizer or nutrient booster to your pond or tank, factor in its impact on other living things in your aquatic environment, such as other plants or fish. If in doubt, your best bet may be to fertilize water lettuce separately.

Water Lettuce Types

  • Pistia stratiotes 'Ruffles': As suggested by its name, this variety sports ruffled leaves. It does not grow as large as other varieties, making it an excellent choice for smaller containers.
  • Pistia stratiotes 'Jurassic': This variety produces foliage rosettes that can grow up to 12 inches wide. Though larger than most, it is not a fast grower. 
  • Pistia stratiotes 'Splash': This variety boasts beautifully variegated leaves and stays small. It is a rare variety and may be hard to find.

Pruning

The rapid growth and invasive nature of water lettuce require that you prune away runner plants to prevent this vegetation from taking over your pond or water feature. This will usually need to be done every week. In addition, removing the larger mother plants will help slow the spread if you have an abundance of water lettuce.

Propagating Water Lettuce

To add water lettuce to a pond or water garden, spread this floating plant on the water's surface in the spring. Ideally, choose a spot with no current, as these plants do not grow well in moving water. If there is a current in your water environment, separate the water lettuce from the current using a floating dam. Items like plastic tubing and suction cups attached to the edges of a tank, a hula hoop, rocks, or a fishing line work well for this purpose.

Since it's such a prolific spreader, propagating water lettuce is simple and easy. Here's how: 

  1. Using sharp snips, cut the stolon connecting the mother plant to the daughter plant. Daughter or runner plants are vegetation offshoots from the main plant. It will produce its own root system. 
  2. Place the daughter plant in its new environment. These plants typically thrive but can become invasive if left unchecked. 

How to Grow Water Lettuce from Seed

Starting water lettuce from seed is not common, but it is doable. If you have seeds, here is how to start them: 

  1. Bury the seed lightly in sand.
  2. Cover the sand and seed with water. 
  3. Keep the sand and seed submerged in water.
  4. The seed will sprout and eventually fill the container. At this point, it's ready to be transplanted into your aquatic environment.

Overwintering Water Lettuce

Water lettuce cannot tolerate cold temperatures. To overwinter a plant, place it in a smaller container of water (such as a fishbowl) and keep it in an area above 50 degrees Fahrenheit. Full sun exposure and occasional fertilization may be necessary. Water lettuce is inexpensive and grows fast, so it is easier and more cost-effective to buy it every year.

Common Pests

Koi and goldfish can kill water lettuce plants by eating their roots. Insects such as the leaf weevil (Neohydronomous affinis) or leaf moth (Spodoptera pectinicornis) also feed on water lettuce.

Common Problems With Water Lettuce

Water lettuce grows easily on its own but is susceptible to environmental factors, such as sun exposure, lack of nutrients, some insects, temperature, salt levels, and pH.

Yellowing or Browning of Water Lettuce

A lack of nutrients will cause water lettuce to grow poorly and turn yellow. Yellowing progresses to browning. You may need to supplement the water with a fertilizer treatment if it lacks nutrients.

Too much sunlight, like full or direct sun on sweltering days, can cause yellowing leaves and leaf scorch.

FAQ
  • Does water lettuce return year after year?

    Water lettuce is a perennial evergreen in tropical and subtropical climates.

  • Can water lettuce survive winter?

    Water lettuce cannot survive frost. Overwinter it by bringing it inside, holding it in a tank or shallow pool with a 70 degrees Fahrenheit temperature with at least 12 hours of bright light, like in a greenhouse.

  • How fast does water lettuce grow?

    Once mature, it is a very fast grower. This plant’s foliage only grows about 6 inches tall, but its dense root system under the water can grow up to 20 inches deep. Unchecked, it can cover a large pond surface in one growing season.

  • Can you use water lettuce in an home aquarium?

    Water lettuce is a vigorous grower with broad water condition tolerances, making it a good low-hassle plant for home tanks.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Pistia stratiotes. North Carolina State Extension.

  2. Pistia stratiotes. U.S. Geological Survey, Nonindigenous Aquatic Species Database, and NOAA Great Lakes Aquatic Nonindigenous Species Information System.

  3. Water lettuce. Center for Invasive Species and Ecosystem Health.

  4. How to control water lettuce. Texas A&M Agrilife Extension.