Hydrocleys nymphoides
Common Name: water poppy 
Type: Herbaceous perennial
Family: Alismataceae
Native Range: Tropical South America
Zone: 9 to 11
Height: 0.50 to 1.00 feet
Spread: 1.00 to 5.00 feet
Bloom Time: June to August
Bloom Description: Yellow
Sun: Full sun
Water: Wet
Maintenance: Low
Suggested Use: Water Plant, Rain Garden
Flower: Showy


Winter hardy to USDA Zones 9-11. In the St. Louis area, plants may be grown in greenhouses or outdoors during the growing season with indoor overwintering. For outdoor use, site plants in moderately fertile wet loams in pond margins or in soil bottoms that are 6-10” below the water surface. Container may also be placed on the soil bottom. Best growth usually occurs in approximately 6” of water. Plants sited in pond margins will send out floating stems into the water. Propagate by dividing off floating stems that have produced roots (rooted plantlets). Plants may be grown from seed, although seed is often difficult to harvest. Sow the seed in shallow pans, sprinkle sand on top and submerge the pans in 1-2” of still water. If overwintering is desired, bring plants indoors before first frost to a shallow tub or aquarium in strong light.

Noteworthy Characteristics

Hydrocleys nymphoides, commonly called water poppy, is a deciduous, stoloniferous, aquatic perennial. It is native to Central and South America, but has been introduced into and naturalized in some areas of Florida and Texas. It features shiny, thick, rounded, dark green leaves (2-4”) that typically float on, but occasionally rise above, the water surface. Leaves have heart-shaped bases. Single, 3-petaled, yellow flowers (2” diameter) with reddish-brown centers and numerous black or brown stamens rise up above the water surface. Plants flower in summer in water that has reached at least 70F. Flowers typically last only one day, but plants bloom in succession over a long summer period. Plants send out floating plant runners on the water surface that sprout new foliage and roots. Flowers are most frequently produced on the runners. Plants provide good surface cover. In St. Louis, water poppy is not invasive, but in warm winter climates not subject to frost it can become somewhat weedy.

Genus name comes from the Greek words hydor meaning water and kleis meaning a key.

Specific epithet means resembling the genus Nymphaea.


No serious insect or disease problems.


Ponds or water gardens.