Grow water lettuce in still or slow freshwater in sun. Water lettuce is Pistia. It is not garden lettuce.
Give it still water and sun
| Factor | Recommended | Avoid |
|---|---|---|
| Light | Full sun or part sun; give midday shade in the hottest stretch so the leaves do not bleach | Do not expect a tight rosette in deep shade |
| Water | Still or slow freshwater, with the crown sitting on the surface | Do not set it in a fountain, a fast current, or a dry bed |
| Site | A lined pond, a water garden, or a still patio tub | Do not stock it where your state lists it as prohibited |
| Winter | Treat it as an annual where frost hits, or lift a few rosettes into a bright indoor tub of still water before the first freeze | Do not leave the rosettes out in a freeze and expect them back |
Water lettuce wants still or slow freshwater and sun. A dry crown dies, and a fountain or a fast current flips the rosette and keeps the leaves wet, which is how they rot. [1] Some states ban sale or possession, so check before you buy. In a freeze the tops collapse; treat the pond planting as an annual, or lift a few rosettes indoors. [2] water lettuce is Pistia stratiotes, a fuzzy, ribbed floating rosette with feathery roots hanging in the water. It is not a salad crop and not a rooted bog plant. A tank with a filter is on Water Lettuce in an Aquarium.
Does water lettuce need full sun?
Full sun or part sun. In the hottest stretch, midday shade keeps the pale leaves from bleaching. Deep shade makes a loose, slow rosette.
Float a rosette after the last frost
Start water lettuce by floating a healthy rosette on the pond after the last frost, with the roots hanging down. This is a surface plant, so it does not need potting mix for the floating form. Daughter plants form on short runners in warm still water.
- Wait until the water stays warm after the last frost, then float a healthy rosette on the surface, roots down.
- Pick off yellow or smashed leaves before you set it out.
- Do not bury it in mud or potting mix if you want a floating mat. [3]
- If wind or a skimmer keeps shoving it around, hold a small group with a floating hoop so the crown can sit still.
Do I plant water lettuce in soil?
Not for the floating mat. Set the rosette on the water. Burying a floater in mix is the wrong start.
Keep a thin mat, and never toss extras into a lake
Once the mat covers about half the water, scoop extras with a net. Compost them well away from the pond, or bag them for the trash, so fragments cannot wash back in. Never toss extras into a lake, a ditch, or a storm drain. In warm still water the colony spreads on runners, so skim on a regular day, not after the surface has already closed. [4]
- When the mat covers about half the pond, scoop extras with a net.
- Compost them far from the water, or bag them for the trash, so pieces cannot wash back in.
- Never toss extras into a lake, a ditch, or a storm drain.
- Leave open water so fish and submerged plants still get light.
Can I toss extras in a nearby lake?
No. Bag extras or compost them away from water. A fragment can start a new mat in a public pond.
Not garden lettuce — and not water hyacinth
Garden lettuce is Lactuca, a soil crop grown for leaves you eat. See How to Grow Lettuce. Water lettuce is a floating pond rosette with velvety, ribbed leaves and hanging roots. It is not a salad, and a query about how often to water lettuce is the garden crop, not this plant.
Water hyacinth has glossy leaves on swollen, air-filled stalks and, when it blooms, a spike of purple flowers. Water lettuce has no swollen stalks and no showy flower spike. Duckweed is a tiny oval frond — see How to Grow Duckweed. American frogbit is a heart-shaped native floater — see How to Grow American Frogbit. A water lily is rooted, with round pads — see How to Grow Water Lily. Bags labeled tropical duckweed are still this plant, not duckweed.
Is tropical duckweed a different plant?
No. Tropical duckweed is another shop name for water lettuce. True duckweed is the tiny oval frond on How to Grow Duckweed.
Set water lettuce on still water in sun, float a rosette after the last frost, and skim extras so the mat never closes the pond.
FAQ
Can I grow water lettuce in a patio tub?
Yes, if the tub holds still water in sun and never dries. A draining flower pot of mix is the wrong home.
Will it come back after frost?
A freeze kills the rosettes. Treat the pond planting as an annual, or lift a few into a bright indoor tub of still water before the first freeze. The tank method is on Water Lettuce in an Aquarium.
Can I grow it from seed?
Seed can sit through a mild winter and sprout, but the shop start is a rosette. Float a plant; do not wait on a packet.
Is it toxic to pets?
Yes if it is eaten. The leaves hold calcium oxalate crystals that burn the mouth. Keep pets from chewing the rosettes.
Does a full mat keep mosquitoes out of the pond?
No. A closed mat can hold water that mosquitoes use. Skim so the surface stays open. Do not stock this plant as mosquito control.
Is it legal in my state?
Some states ban sale or possession. Check before you buy, and never move extras into a public waterway.
Can I grow water lettuce in an aquarium?
Yes, in still tank water under strong light. That method is on Water Lettuce in an Aquarium.
Related guides
Recommended plants
References
- [1] NC State Extension Gardener -
https://plants.ces.ncsu.edu/plants/pistia-stratiotes/ - [2] UF/IFAS Center for Aquatic and Invasive Plants -
https://plant-directory.ifas.ufl.edu/plant-directory/pistia-stratiotes/ - [3] Gardening Know How -
https://www.gardeningknowhow.com/ornamental/water-plants/water-lettuce/water-lettuce-in-ponds.htm - [4] Wisconsin Department of Natural Resources -
https://dnr.wisconsin.gov/topic/Invasives/fact/WaterLettuce.html
This note is part of Pistia Guides.
More first-season notes by plant are gathered in How to Grow Guides.
Updated: Reviewed by Bosquelle Editors