Ornamental · Alismataceae
Water Poppy
Hydrocleys nymphoides
Give it full sun and warm, still water, and the water poppy floats out glossy leaves and bright yellow blooms all summer.
Full sun
50–90°F · 10–32°C
USDA 9–11
6–12 in · 15–30 cm
Overview
Water poppy is a small floating pond plant that earns its name from looks alone. The glossy heart-shaped leaves ride on the surface like a miniature lily, and through the warm months it lifts up cupped yellow flowers that each last only a day before the next takes over. It belongs to the water-plantain family and comes from the warm waters of Central and South America.
Grow it in a pot of heavy aquatic soil sunk into a few inches up to about a foot of still water, and keep the crown under the surface. Given warmth and sun it grows fast, trailing stolons across the water and rooting new plantlets as it goes. That speed is the catch worth knowing about. In frost-free climates it can turn weedy and invasive, so it stays in a container and never goes into a wild waterway.
None of this makes it hard to keep. The plant asks for little beyond sun, warm water, and the odd thinning, and it shrugs off pests apart from the occasional run of aphids. Its one real weakness is cold, since the first frost finishes it.
Care
The short version: full sun and warm, still water a few inches up to about a foot deep, the crown kept submerged in heavy aquatic soil, a monthly feed in the growing season, and the pot brought indoors before frost.
Light
Give water poppy full sun, six or more hours of direct light a day. It will limp along in part shade, but the flowers thin out fast, so the brighter the spot the better the bloom.
Water
This is an aquatic plant, so it lives in standing water. Sink the pot in a few inches up to about 12 inches of warm, still water and keep the crown under the surface at all times. The water needs to be calm rather than moving.
Soil
Pot it into heavy aquatic loam or clay in a container made for ponds. It isn't fussy about texture and takes clay, loam, or sand, holding to a pH band of 6.0 to 7.5.
Temperature
It runs best in warm water, roughly 50°F to 90°F (10°C to 32°C). Growth slows in the cold, and a frost kills the plant outright, so warmth is the thing to watch.
Humidity
Living in open water, water poppy never wants for moisture, so there's no humidity figure to chase. The water itself does all the work here.
Feeding
Through spring and summer, push an aquatic fertilizer tablet into the soil container about once a month. Feeding the soil rather than the water keeps the nutrients where the roots can use them and out of the open pond.
Pruning
There's little to do beyond tidying and curbing the spread. Thin out the trailing stolons and pull off yellowing leaves to keep the plant in bounds and stop it blanketing the surface.
Repotting
Repot every spring, or whenever the container fills with roots. Matted roots, fewer flowers, and stolons climbing out of the pot all tell you it's time to divide and give it fresh soil.
Size & spacing
Each plant stands only 6 to 12 inches (15 to 30 cm) above the water but spreads 1 to 5 feet (30 to 150 cm) across as the runners travel. Plan for that reach and keep it potted so it doesn't take over.
When to plant
Water poppy runs on warmth and stops dead at the first frost. Hold it indoors or start fresh in late winter, set it out only once the cold has passed and the water has warmed, and it blooms right through the summer.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Late winter to early spring (seed propagation is difficult; division is preferred)
- Plant: After all danger of frost has passed and water has warmed, late spring to early summer
- Harvest: Summer (June to August), beginning when water reaches about 70 degrees F
Hardiness
USDA hardiness zones: 9–11
Temperature: down to -7°C
Troubleshooting
Most water poppy trouble traces back to cold water, too little sun, or the plant's own galloping vigor. Read the early signs and you can step in before a small issue takes over the pond. Match what you see below, then act while it still helps.
Leaves turn mushy or black after a cold snap
Water poppy is tender and won't survive a frost. Below zone 9, or whenever the water turns cold, the plant stops growing and the foliage goes translucent and slimy. Lift the pot indoors to a bright, warm tub before the first frost, or simply treat the plant as an annual and start again in spring.
Fix:
- Before first frost, lift the container and move it indoors to a shallow tub or aquarium with bright light and warm water
- Overwinter as a houseplant or treat as an annual and replant in spring
Runners and plantlets blanket the water surface
In warm, frost-free water the plant runs hard, rooting at every node and throwing off new plantlets that close over the surface in no time. This is normal vigor, not a disease, but left alone it crowds out everything else. Grow it in a sunken pot rather than open pond mud, thin the runners on a regular basis, and never tip spare plants into a wild waterway.
Fix:
- Grow in a contained pot rather than planting directly in pond mud
- Regularly thin and remove excess stolons and plantlets
- Do not release into natural waterways
Plenty of leaves but hardly any blooms
A leafy plant that won't flower is almost always short on sun or sitting in water that's still too cold. Blooming kicks in once the water warms to about 70°F (21°C), so move the pot into six or more hours of direct light and be patient. A monthly aquatic fertilizer tablet pushed into the soil helps once the warmth arrives.
Fix:
- Move the container to full sun (6 or more hours of direct light)
- Wait for water to warm to about 70 degrees F
- Fertilize with aquatic fertilizer tablets
Sticky leaves and clusters of small soft-bodied bugs
Those tiny insects on the emergent foliage are aphids, and the sticky film they leave behind is honeydew. Blast them off with a strong jet of water or wipe the colonies away by hand. Skip the chemical sprays, since they poison fish and the rest of the pond life, and let natural predators finish the job.
Fix:
- Spray aphids off foliage with a strong stream of water
- Wipe or hand-remove colonies
- Avoid chemical pesticides that can harm pond wildlife and fish
Toxicity
Good news for a household with animals: water poppy is non-toxic and considered safe around pets, livestock, and children. Sitting out in deep water, it's rarely within reach anyway, and a stray nibble of the wet leaves does nothing worse than a passing tummy upset.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
No toxin here, so a curious cat is in no danger. A mouthful of the wet foliage might bring a little drool or a queasy stomach, and that passes on its own.
Dogs None
Safe for dogs, with nothing in the plant that poisons them. The worst a determined chewer faces is mild, short-lived stomach upset from the soggy leaves.
Horses Safe
Horses can graze the foliage without harm. It carries no known toxin, and a pond plant rarely sits within reach of a paddock anyway.
Rabbits Safe
Rabbits won't be poisoned by a nibble of the leaves. Offer only small amounts of any unfamiliar greens, since a sudden change of diet can loosen a rabbit's gut.
Livestock Safe
Cattle, goats, and sheep can browse it safely. The plant holds no toxin, though its place in deep water keeps it well out of most grazing animals' way.
Birds Safe
Backyard and pond birds come to no harm from the foliage or flowers. Waterfowl often pick at the soft growth without any trouble at all.
People Safe
The plant poses no poisoning risk to people. It isn't grown to be eaten, so there's no reason to make a meal of it, but a child who tastes a leaf will be fine.
As an aquatic pond plant it is rarely accessible to pets; pets that nibble aquatic foliage may experience mild, self-limiting gastrointestinal upset.
Varieties
There's really just one water poppy to grow. The plain species is what fills ponds everywhere, with no named cultivars to pick from.
Hydrocleys nymphoides (species)
This is the plain species grown in nearly every pond, with glossy heart-shaped leaves floating on the surface and yellow three-petaled flowers that give it the poppy name, and there are no named cultivars to choose between.
How to propagate
Water poppy all but multiplies itself, and you'll get free copies far quicker by dividing a plant you already have than by fussing with seed.
DivisionEasy
Spring to summer during active growth · A few weeks
By far the easiest way to make more water poppy. While the plant is growing through spring and summer, snip off the rooted plantlets that form along the trailing stolons and pot each one into aquatic soil, where it settles in within a few weeks.
SeedDemanding
Spring · Several weeks to months
Starting from seed in spring works, but it's slow and fiddly, taking anywhere from several weeks to a few months to get going. Most growers skip it and divide an existing plant instead.
Myths
Water poppy is a true water lily or a kind of poppy.
It is neither. Hydrocleys nymphoides belongs to the water-plantain family, and it only looks the part, floating like a little lily and opening yellow flowers shaped like a poppy's. The name is pure resemblance, with no kinship to real water lilies or to the poppies of the garden.