Taxonomy and origin
The water lily is a rooted aquatic perennial: a fleshy rhizome anchored in the soil at the bottom of a pond, with leaves and flowers riding on the surface or lifting just above it. Counts of the family vary between authorities, from 65 water lily species worldwide to about 70 known species spread across five genera. The pad everyone recognizes is round to oval, cut by a single V-shaped notch where the leaf stalk joins the blade, and on the white species native to the American Midwest it runs 8 to 16 inches across. Leaves and stems are spongy, green on the upper surface and purple or red underneath, and the tissue inside is riddled with air pockets, the way an aerated chocolate bar is. That structure is what keeps a pad floating flat while it carries rain, insects and the occasional frog. Flowers come one to a stalk, and depending on the type they either float at the surface or stand above it.
Wild water lilies cover more of North America than most pond owners assume. The fragrant white species is native to the eastern half of the continent, southern Canada included, and it turns up in water from Florida and Puerto Rico to Alaska. Garden water lilies, though, divide into two groups that behave nothing alike. Hardy types descend from temperate species and are kept as permanent pond plants in cold-winter states; tropicals need warm water to start and warm water to keep going, so most of the country handles them as summer stock. How deep to sink the pot, what to do in October and whether the plant returns are all answered differently for the two groups. Color follows species and breeding. Among the wild American species, Nymphaea mexicana carries yellow flowers, N. elegans light purple and yellow, and N. odorata white and yellow. In the wild, N. odorata opens bright white and deeply fragrant, and hybridizing has since pushed the garden forms into yellow, pink and light purple as well, which is why a pond can be planned around a single shade the way a border of white flowers is. A single bloom carries 17 to 43 petals, white and sometimes pink, layered in rings that open outward from the center, which is why a water lily reads as a full flower even from across the water.
Water lily or lotus: how to tell them apart
Check the leaf first. A water lily pad lies flat on the water and carries a distinct notch where the stalk meets the blade, while a lotus leaf has no notch at all and is usually held up on a stem above the surface. Touch is the second test: water lily flowers and leaves are thick and waxy, and a lotus is thin and papery. Petal shape settles it, pointed on a water lily so the open flower reads as a star, rounder and sometimes ruffled on a lotus. Scent separates them too: a water lily is at its strongest the moment the flower opens and fades from there, while lotus fragrance stays subtle throughout. After bloom the two are unmistakable. A spent water lily flower wilts and sinks below the water, and a lotus leaves behind a seed pod that keeps growing above the surface once the flower has passed. The two are not close relatives, whatever a photograph suggests: the sacred lotus was long filed with the water lilies and now stands in a family of its own, Nelumbonaceae, in a different order of flowering plants altogether.
Bloom time
Water lilies flower through the warm months, and the start date depends on which type is in the pot. A hardy cultivar such as 'Marliacea Chromatella' opens in May and carries on until frost. A tropical such as 'Director George T. Moore' waits for summer heat and runs from June to frost. The wild white species of the Midwest is later than either, blooming July through October. Buds rise on their own stalks from the crown and open among the pads, and a settled plant keeps sending up replacements, which is what makes a pond look continuously in flower even though no single bloom lasts long. Each 'Marliacea Chromatella' flower stays in play about five days, and each 'Director George T. Moore' about three to four days. The daily open and close has a job behind it: male and female parts of the flower are usually active at different times, which moves pollen between flowers and keeps the plants crossing. The practical effect is that the display runs on daylight, so a pond looked at only after work in late summer can seem to have quit blooming when it has not. Weather moves both ends of the season. The first flowers wait on the pond warming in spring and the last are taken by frost, so a cold May or an early freeze shortens the show at whichever end it hits.
Hardy or tropical: which water lily is in the pond
Nearly every care decision splits on this question, and the answer shows in the pot, the pad and what happens in October. Four plants turn up in American water under the same common name.
Planting a water lily in a pond or tub
A water lily goes into a wide, shallow container of heavy soil, and the container goes into the pond, which keeps the plant liftable, easy to feed and where you put it. Suitable planting media are clay, loam or silt, and soils high in organic matter. Set a hardy rhizome horizontally on the soil in spring with the bud end up, in a container that will sit 12 to 48 inches below the surface. Pot width counts for more than pot depth here, because the rhizome lies down and travels sideways as it grows. Fill the pot most of the way, top the soil with pea gravel and keep the gravel clear of the growing point. The cap holds the soil in the pot and keeps the water clear when the fish come past.
Depth is the number most often gotten wrong, and published figures genuinely disagree. New York Botanical Garden puts water lilies in 2 to 5 feet of water, while pond growers keep most cultivated plants at around 6 to 18 inches over the crown. Both figures describe real plants in different settings, and the way through is to start shallow and work down. Put a new rhizome in at about 6 inches of depth, let it root and throw pads that reach the surface and lie flat, then lower the pot in stages if the spot calls for it. Where the pond floor sits deeper than the plant wants, the pot goes on a pedestal, a stack of bricks or an upturned crate, at whatever height brings the crown into range. Tropicals start warmer: the container goes into 6 to 12 inches of water once the pond has warmed to about 75 degrees Fahrenheit.
Site the pot in calm, open water. In the wild these are plants of ponds and slow-moving streams, and a pad taking spray from a fountain or a waterfall all day never settles flat. The middle of the pond belongs to the lily, and the shallow shelf at the edge is where a marginal such as water iris goes. Sun is the other siting decision, and it is the one that cannot be corrected later without moving the pond itself. The same rules scale down to a half barrel or a glazed bowl on a patio: a single dwarf lily to a pot, gravel on top, a few inches of water over the crown, and a canna lily in its own pot beside it when the group needs height. Bare-root plants shipped in spring arrive looking like a cut root with one bud on it, and they go into soil the day they land.
Pot width and water depth by lily size
Pot width follows the size class printed on the tag, and the water over the crown follows the pot.
Why a water lily will not bloom
A water lily that makes pads and no flowers is usually short of light, sitting too deep, or short of food, and the checks run in that order. Hardy water lilies need at least 5 hours of sun a day in fertile loamy soil, along with regular feeding, so a pond in shade for a good part of the day gives leaves and stops there. Depth comes next. A pot resting on the floor of a deep pond holds the crown a long way from the light, and shallower placement is where the flower count rises, which makes raising the pot on bricks the first correction to try. Read the pads for the answer: pads that reach the surface and lie flat with slack in their stalks say the depth is right, and pads that arrive stretched tight, or never arrive at all, say the pot is too low.
Food is the cause that catches owners whose plants look healthy. A lily can hold a potful of green pads and still be running on empty, since it works through only a few gallons of soil, and two or three aquatic fertilizer tablets pressed into that soil at each feeding is what pond growers use to bring flower color up. Crowding is the same story told slower. A hardy lily fills its basket with rhizome, and dividing and repotting it every 1 to 2 years, as soon as the pot is full, is what keeps it flowering. Two more causes have nothing to do with care. Moving water from a fountain or a waterfall keeps the pads unsettled, and fish working the pot can lift a rhizome clear of the soil before it ever sets a bud.
Working out why the flowers stopped
The checks run cheapest and most likely first, and each one is something you can look at this afternoon.
Winter care
A hardy water lily spends the winter in the pond, below the ice. Cut the collapsing pads away in fall and move the container to the deepest water available, so the crown sits under the ice line: hardy lilies come through a St. Louis winter without trouble as long as the water does not freeze solid around them. That single condition explains why a deep pond is easier to overwinter than a shallow water garden. Where the pond is too shallow to keep liquid water at the bottom, or where the whole thing is a tub that freezes through, the container comes out and spends the winter indoors at 40 to 45 degrees Fahrenheit, kept dark and damp in a basement or an attached garage.
A tropical water lily is a different plant in October. It is hardy only in zones 10 to 11, which means that everywhere else it gets lifted, stored, or bought again in spring, and plenty of pond owners treat the third option as the sane one. Those who keep theirs let the plant take one or two frosts first, which helps push the tuber into dormancy, then lift the pot, wash the tuber clean and strip away the old leaves and roots. Storage methods disagree from there, and both come from people who do this every winter. One holds the tubers in jars of distilled water in a basement that stays in the 50s Fahrenheit. The other packs them in damp sand at 55 to 60 degrees, with viviparous varieties keeping better at 60 to 65. The sand is meant to be barely damp, at the moisture level of pipe tobacco, which is drier than it sounds. A third route skips the washing: the plant stays in its pot with the soil barely moist, in a cool but protected place such as a garage. All three end the same way. In spring the tuber is started in a 3 to 4 inch pot of soil in water held at 65 degrees Fahrenheit or warmer, and it goes back into the pond once it has leaves and roots enough to hold its own.
Winter by zone
Zone decides how cold the water gets, and type decides whether the plant can sit in it.
Koi and what else eats a water lily
Koi and water lilies can share a pond, and every protection that works is physical. Start with an oversized container topped with gravel and add a cage of PVC-coated wire, plastic mesh or netting over the pot so the fish cannot reach the soil. Stocking several plants at once gives them better odds than adding one or two at a time. The fish also have preferences worth using: water lettuce, lotus, water poppy and umbrella plant tend to be left alone in favor of more palatable choices, so a pond that gives koi something else to graze loses fewer pads. A wide, heavy pot that a fish cannot tip belongs on the same list.
Fish are not the only mouths on the plant. Deer, beaver, muskrat, nutria and other rodents eat both the leaves and the rhizomes of the native white water lily, and deer take the leaves of the yellow Mexican species from time to time, which matters most around farm ponds and natural shorelines. The plant gives something back: the undersides of the floating pads work as nurseries for aquatic insects and snails, and those in turn feed and shelter small fish, which is the part of a lily pond a fish keeper notices in high summer when everything in the water is looking for shade.
Water lily varieties worth knowing apart
Two facts decide where a named lily can live: how much surface it covers and whether it survives a frozen pond. Both are on the label if you know to look.
How far a water lily spreads, and where it is a weed
Put a water lily straight into pond mud and it will keep going. The rhizomes that carry it through the sediment are mostly 1 to 1.19 inches thick and branch as they travel, so a single crown becomes a colony without anyone planting a second plant. Left alone, the fragrant white species forms dense stands covering hundreds of acres. Inside its own range that is a native plant doing what natives do: it is the one native water lily of Missouri, turning up sporadically nearly statewide. West of that range the same species is treated as a problem, and Washington State classifies fragrant water lily as a Class C noxious weed, added to the list in 2002. The practical line for a garden pond runs through the pot. A lily kept in a container stays a plant you own; the same lily loose in an earth-bottom pond becomes a management job, and pieces of rhizome moved between water bodies are how it travels.
Light
A water lily wants full sun, and for this plant that means 6 or more hours of direct sunlight a day, counted on the water itself, since a sunny patio can sit beside a shaded pond. A pond receiving 2 to 6 hours falls into partial shade, which is enough light to keep a lily alive and not enough to keep it in flower. Shade usually arrives from something the pond owner cannot move: a fence line, a garage wall, a maple that was smaller when the pond went in. Since the pot can be moved and the tree cannot, siting starts with the pot, and any marginal plant that tolerates shade takes the darker shelf. A pond in deep shade grows algae and frogs perfectly well; it does not grow a flowering water lily.
Feeding and what goes in the pot
Water lilies are fed with fertilizer tablets pushed down into the pot's soil, and the published schedules do not agree on how often. The instructions run from every 2 to 4 weeks for a tropical cultivar to every 4 to 6 weeks, with two tablets per gallon of soil every four weeks until fall in between. The spread between those numbers is smaller than it looks, because all three land on roughly monthly feeding through the growing season and all three stop when growth stops. There is also a version that removes the counting: press the tablets 3 to 4 inches into the soil on the 1st and 15th of the month, which suits anyone who feeds by calendar. Soil chemistry is the easy part. Hardy water lilies do well across a broad neutral band, roughly pH 6.0 to 8.0, so a pot filled with garden clay or loam rarely needs correcting. What the soil must not be is loose and floaty, since anything light rises out of the pot and clouds the pond the first time a fish swims past.
How big a water lily gets
A water lily has almost no height, so its size is a question of how much water one plant covers. A medium hardy cultivar such as 'Marliacea Chromatella' spreads 5 to 6 feet across the surface from a single crown, which is more pond than most people picture when they carry home one pot. That figure is the one to check before buying, because a plant sized for a farm pond will cover a preformed liner completely and leave the fish in permanent shade. The flowers stay in proportion to the pads. Hardy garden lilies open 3 to 6 inches across, built from petals reaching up to 3.16 inches long on the wild white species, and the bloom is followed by a fruit 1 to 1.19 inches in diameter, which is the part most pond owners never notice.
Aphids and the moth that cuts the pads
Two insects do nearly all the visible damage to a water lily. The waterlily aphid has been in American ponds since it was first recorded in North America in 1890, and it works its way through a colony of pads in warm weather. A pond usually settles the matter itself, since ladybugs, syrphid flies and parasitoids all feed on the aphid and arrive once there is something to eat. The China mark moth is the more destructive of the pair. Its larvae pass through four instars, and the late ones cut pieces out of the pads and build cases 0.5 to 0.75 inch long to live inside, which is why the damage looks like vandalism with no culprit in sight. The adult moth is easy to miss at about a 1-inch wing spread. Where the population needs knocking down, University of Maryland Extension names the Bacillus thuringiensis 'Kurstaki' strain and the insecticide spinosad as effective against the larvae.
What actually goes wrong, in the order pond owners report it
Ordered by how often they came up across thirty-seven pond threads and posts, most of them on garden pond and koi forums.
Seven threads. Symptoms: a full pot of green pads and no buds, or buds that swell and stay shut. Management: sun, then depth, then food, then the size of the pot, in that order.
Seven threads. Symptoms: shredded pads floating loose, soil clouding the water, a rhizome lifted clear of the pot. Management: physical protection at the pot, since nothing about the fish changes.
Seven threads, split between hardy plants in ponds too shallow to hold liquid water and tropical tubers in storage. Symptoms: rot in the storage box. Owners trace it to sand kept too wet.
Five threads. Symptoms: a medium lily bought for a tub, pads climbing the rim and standing above the water. Management: check the size class on the tag against the pot you actually have, before the plant is in the water.
Three threads, all about earth-bottom ponds with no container. Symptoms: pads across open water within a couple of seasons and no clear edge to the stand.
Three threads. Symptoms: colonies on the tops of the pads and on the buds after a warm spell, with sticky pads underneath them.
Two threads. Symptoms: pads yellowing one at a time while new ones keep arriving, or pads held clear of the surface on stiff stalks. As pond owners report it, standing pads follow a pot that has run out of room.
The water lily in art and in the record books
The water lily reached most people through one painter and one enormous leaf. Claude Monet produced more than 250 paintings featuring water lilies, nearly all of them worked from the pond he built himself, and that pond is why a still green surface broken by pink and white flowers reads as a picture before it reads as a plant. The record books belong to a different plant, the giant Victoria, whose leaves measure up to ten feet across and get tested every summer at a weigh-off run by Denver Botanic Gardens. The winning pad held 183 pounds before it went under, with entries of 182 and 176 pounds close behind, in a contest drawing more than 40 participants across nine countries. A leaf carries that much because the ribs radiating from its center and the cross veins between them trap pockets of air that spread the load over the whole pad, which is the same trick, at a different scale, that keeps an ordinary lily pad flat on the water.
What people get wrong about water lilies
Five beliefs that send pond owners after the wrong fix.
The myth: Hardy lilies float their flowers and tropicals hold theirs up, so the flower tells you which is which.
The reality: Plenty of hardy cultivars carry flowers above the water: 'Texas Dawn', 'Charlene Strawn' and 'Pink Sensation' all do it.
The myth: Neat round holes in the pads mean fish or turtles.
The reality: Shot holes 0.25 to 0.75 inch across are China mark moth larvae, and the late ones move on from holes to eating the entire leaf.
The myth: A few aphids on a pad will pass on their own.
The reality: One waterlily aphid mother turns out about 50 offspring at two to four a day, and her nymphs are mothers themselves in about a week.
The myth: One water lily cannot take over a pond.
The reality: It can take over a shallow lake, which is why pond guidance calls for containers or isolated shallow islands.
The myth: Water lilies are tropical plants.
The reality: Some grow as far north as zone 3 or 4, while the lotus they get confused with is hardy only to zone 9.
What to expect, season by season
A water lily is slow to convince and then hard to stop.
Planting year: pads come before flowers. A bare-root rhizome set out when the water warms spends its first weeks pushing leaves toward the surface, and the earliest ones may sit submerged and look drowned while the plant finds the light. Flowers follow once the pot has some root in it, and a plant that went in during high summer flowers late or not at all in its first season. Feeding starts as soon as growth does.
Second year: this is the year the plant pays. The pot is full of root, the pads cover the water they are going to cover, and bloom runs from the first warm weeks to the first frost with new buds replacing spent ones the whole time. Nothing needs doing beyond feeding, cutting away pads as they collapse, and keeping the fish off the soil.
Third year and after: flowers get smaller and fewer as the rhizome fills the basket, which is a scheduling problem the plant hands you on time. Divide and repot as soon as the pot is crowded, and work three to five fertilizer tablets into the top of the fresh soil to start the plant again.
Flower photos
FAQ
How deep should a water lily be planted?
Set a new plant at about 6 inches of water over the crown and lower it later if the spot calls for it. Most cultivated water lilies do well anywhere from 6 to 18 inches over the crown, and the shallow end of that range is where the flowers are.
Do water lilies come back every year?
Hardy ones do, as long as the water around the pot does not freeze solid. Tropicals are hardy only in zones 10 to 11, so everywhere else they are lifted and stored, kept indoors, or bought again in spring.
What is the difference between a hardy and a tropical water lily?
The plant part and the water temperature. A hardy lily grows from a rhizome laid flat in the pot and winters in the pond; a tropical grows from a tuber and goes out only once the water reaches about 75 degrees Fahrenheit.
Do koi eat water lilies?
They graze the pads and dig at the pots. The protections that work are physical: an oversized container with gravel over the soil, and a cage of PVC-coated wire, plastic mesh or netting across the top of the pot.
What kills water lilies in a pond?
Cold that reaches the crown, fish that dig the rhizome out of its soil, and China mark moth larvae, whose late instars eat the whole leaf. Rot in winter storage accounts for most of the tropicals that never come back.
What is the best fertilizer for water lilies?
Aquatic fertilizer tablets pushed down into the pot's soil, where the roots are. One schedule presses them 3 to 4 inches into the soil on the 1st and 15th of the month; another gives two tablets per gallon of soil every four weeks until fall.
How much sun does a water lily need?
Six or more hours of direct sun a day counts as full sun for a water lily. At 2 to 6 hours the pond is in partial shade, which is where plants make pads and skip the flowers.
Is a water lily the same thing as a lotus?
No. The quickest tell is the leaf: a water lily pad has a notch where the stalk meets the blade and a lotus leaf has none. The sacred lotus was once filed with the water lilies and now sits in its own family, Nelumbonaceae.
What size water lily fits a patio tub or a small pond?
A small or dwarf one, which goes into a container 10 to 12 inches wide. A medium plant wants a pot 14 to 18 inches across, more than a half barrel can give it once the gravel and water are in.
How often do water lilies need dividing?
Every 1 to 2 years, as soon as the pot fills with rhizome. Work three to five fertilizer tablets into the top of the fresh soil when the divided piece goes back in.
Are water lilies good for pond fish?
At moderate density, yes. The plant makes excellent habitat for fish and other aquatic animals, and the flowers pull in pollinators.
Interesting tips
- If a China mark moth has found your pond once, variety choice is a control in itself. The moth passes over Nymphoides cristatum 'White Snowflake' and Nymphaea 'Mrs. C.W. Thomas', which makes replanting a chewed-out pot an opportunity.
- The aphids on your pads are not lily specialists. The same insect feeds on duckweed, arrowhead, water milfoil, water plantain, cattail, bladderwort, pondweed and rice, so a weedy pond margin keeps supplying them no matter how clean the lily looks.
- Wild plants are no guide to how deep to sink a pot. Fragrant water lily roots in sediment under water six to seven feet deep, reaching the surface with stalk length that a potted garden cultivar does not have to spare.
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