Water lily

A water lily is a rooted aquatic perennial, growing from a fleshy rhizome in the pond bottom. Counts of the species run from 65 to about 70. The pad is round to oval with a single V-shaped notch where the stalk joins the blade, and on the white species of the American Midwest it runs 8 to 16 inches across. Leaves and stems are spongy, green on top and purple or red underneath. The tissue inside is riddled with air pockets, the way an aerated chocolate bar is, and they hold a pad flat under rain, insects and the occasional frog. Flowers come one to a stalk, floating or standing above the water depending on the type.

The fragrant white species is native to the eastern half of the continent, southern Canada included, and it grows from Florida and Puerto Rico to Alaska. Hardy types come from temperate species and stay in the pond for good; tropicals need warm water to start and to keep going, so most of the country treats them as summer stock. Among the wild species, Nymphaea mexicana carries yellow flowers, N. elegans light purple and yellow, N. odorata white and yellow, and breeding has pushed the garden forms into pink and light purple too. That is range enough to plan a pond around one shade, the way a border of white flowers is. A bloom carries 17 to 43 petals in rings opening outward from the center.

Check the leaf first. A water lily pad lies flat on the water with a notch where the stalk meets the blade. A lotus leaf has no notch at all and usually stands on a stem above the surface. Touch is the second test: water lily flowers and leaves are thick and waxy, a lotus thin and papery. Petals are pointed on a water lily, so the open flower reads as a star, and rounder or ruffled on a lotus. A water lily is strongest for scent the moment the flower opens and fades from there, while lotus fragrance stays subtle throughout. After bloom a spent water lily wilts and sinks, and a lotus leaves a seed pod that keeps growing above the surface. The sacred lotus was long filed with the water lilies and now stands in its own family, Nelumbonaceae.

Water lilies flower through the warm months, and the type in the pot sets the start date. The hardy 'Marliacea Chromatella' opens in May and carries on until frost. The tropical '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 and open among the pads, and a settled plant keeps sending up replacements, so the pond looks continuously in flower. Each 'Marliacea Chromatella' flower stays in play about five days, each 'Director George T. Moore' about three to four. The daily open and close has a job behind it: male and female parts are usually active at different times, which moves pollen between flowers.

Nearly every care decision splits on this question, and the answer shows in the pot and in October.

Hardy water lily

The pot stays in the water all winter and the same crown comes up again. A standard cultivar such as 'Marliacea Chromatella' takes zones 4 to 10.

Tropical water lily

Bigger flowers on a plant that quits in cold water. 'Director George T. Moore' opens 7 to 10 inches across with a yellow center. It grows from a tuber and gets lifted or replaced in most of the country.

Wild fragrant white water lily

The unpotted plant in a natural pond, spreading on its own. The white flowers carry enough scent to find the plant by.

Yellow Mexican water lily

Turn a pad over: the underside is purple or deep red. The flowers are small for the group, 2 to 4 inches across.

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. Clay, loam, silt and soils high in organic matter all work. Set a hardy rhizome flat on the soil in spring, bud end up, in a container that will sit 12 to 48 inches below the surface. Width matters more than depth in a pot, because the rhizome lies down and travels sideways. Fill the pot most of the way and cap the soil with pea gravel, clear of the growing point, so nothing clouds the water when the fish come past.

Start a new rhizome at about 6 inches of water over the crown, let it root and throw pads that lie flat, then lower the pot in stages if the spot calls for it. Most cultivated plants settle at 6 to 18 inches over the crown, in a pond that can run 2 to 5 feet deep with the pot on a pedestal. Where the floor sits deeper, a stack of bricks or an upturned crate lifts the crown back into range. Tropicals start warmer: 6 to 12 inches of water, once the pond has reached 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 never settles flat. The middle of the pond belongs to the lily, and the shelf at the edge is where a marginal such as water iris goes. The same rules scale down to a half barrel: one dwarf lily to a pot, gravel on top, a few inches of water over the crown, and a canna lily beside it for height.

A water lily that makes pads and no flowers is short of light, sitting too deep, or short of food. Hardy water lilies want at least 5 hours of sun a day in fertile loamy soil, with regular feeding. A shaded pond gives leaves and stops there. A pot on the floor of a deep pond holds the crown a long way from the light, and the flower count rises as the pot comes up. Read the pads: flat ones with slack in their stalks say the depth is right, and pads that arrive stretched tight, or never arrive, say the pot is too low.

Food is the cause that catches owners whose plants look healthy. A lily works through only a few gallons of soil, so it can hold a potful of green pads and still run on empty. Two or three aquatic fertilizer tablets pressed into that soil at each feeding bring the flower color back up. Crowding works slower. A hardy lily fills its basket with rhizome, and dividing every 1 to 2 years, as soon as the pot is full, keeps it flowering. Two more causes are not about care: moving water from a fountain keeps the pads unsettled, and fish working the pot lift a rhizome before it sets a bud.

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 you have, so the crown sits under the ice line. Hardy lilies come through a St. Louis winter as long as the water does not freeze solid around them. Where the bottom cannot stay liquid, or the tub freezes through, the container comes out. It winters indoors at 40 to 45 degrees Fahrenheit, dark and damp, in a basement or an attached garage.

A tropical is a different plant in October. It is hardy only in zones 10 to 11, so everywhere else it gets lifted, stored, or bought again in spring. Let the plant take one or two frosts to push the tuber into dormancy, then lift the pot, wash the tuber and strip the old leaves and roots. One storage method is jars of distilled water in a basement that stays in the 50s Fahrenheit. The other is damp sand at 55 to 60 degrees, with viviparous varieties better at 60 to 65. The sand should be barely damp, at the moisture of pipe tobacco. A third route skips the washing and leaves the plant in its pot, soil barely moist, somewhere cool such as a garage. Start the tuber in spring in a 3 to 4 inch pot of soil, in water at 65 degrees Fahrenheit or warmer, and put it back in the pond once it has leaves and roots of its own.

Koi and water lilies can share a pond, and every protection that works is physical. Start with an oversized container topped with gravel, then cage the pot in PVC-coated wire, plastic mesh or netting so the fish cannot reach the soil. Stocking several plants at once gives them better odds than adding one or two at a time. Koi have preferences worth using: they leave water lettuce, lotus, water poppy and umbrella plant alone when something more palatable is available.

Fish are not the only mouths on the plant. Deer, beaver, muskrat, nutria and other rodents eat the leaves and the rhizomes of the native white water lily, and deer take the leaves of the yellow Mexican species too. The plant gives something back: the undersides of the pads work as nurseries for aquatic insects and snails, which in turn feed and shelter small fish.

Two facts decide where a named lily can live: how much surface it covers, and whether it survives a frozen pond.

'Marliacea Chromatella'

Hardy

Flowers up to 5 inches across
Pads up to 8 inches across, floating flat

'Texas Dawn'

Hardy

Bright yellow and lemon-scented
Carries on blooming into fall

'Charlene Strawn'

Hardy

Spreads 2 to 4 feet

'Pink Sensation'

Hardy

Among the best pink hardy lilies

'Director George T. Moore'

Tropical

Spreads 5 to 8 feet
Above the warmest zones it is lifted or replaced

Nymphaea odorata

Native

Flowers 2.4 to 7.5 inches across
Leaves up to 10 inches long

Nymphaea mexicana

Wild species

Leaves up to 9 inches wide
Yellow flowers of about 25 petals

Victoria

Giant

Pads up to ten feet across

Put a water lily straight into pond mud and it will keep going. The rhizomes are about an inch thick and branch as they travel, so one crown becomes a colony with nobody planting a second plant. Left alone, the fragrant white species forms dense stands covering hundreds of acres. Inside its own range it is a native: the one native water lily of Missouri, sporadic nearly statewide. West of that range the same species is a problem, and Washington State classifies fragrant water lily as a Class C noxious weed, added to the list in 2002. A lily in a container stays a plant you own, and the same lily loose in an earth-bottom pond becomes a management job. Broken rhizome is how it moves between waters.

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 and not on the patio beside it. At 2 to 6 hours the pond is in partial shade, which keeps a lily alive and does not keep it in flower. Shade usually arrives from something you cannot move: a fence line, a garage wall, a maple that was smaller when the pond went in. A pond in deep shade grows algae and frogs perfectly well. It does not grow a flowering water lily.

Water lilies are fed with fertilizer tablets pushed down into the pot's soil, where the roots are. Feed about every four weeks through the growing season, two tablets per gallon of soil, and stop when growth stops in fall. Or press the tablets 3 to 4 inches into the soil on the 1st and 15th of the month. Hardy water lilies do well across a broad neutral band, roughly pH 6.0 to 8.0, so garden clay or loam rarely needs correcting.

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. Check that figure before buying: a plant sized for a farm pond will cover a preformed liner completely and leave the fish in permanent shade. Hardy garden lilies open 3 to 6 inches across, on petals up to about 3 inches long in the wild white species. The bloom is followed by a fruit about an inch across.

Two insects do nearly all the visible damage. The waterlily aphid has been in American ponds since it was first recorded here in 1890. 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 does more damage. Its larvae pass through four instars. The late ones cut pieces out of the pads and build cases 0.5 to 0.75 inch long to live inside. The adult is easy to miss at about a 1-inch wing spread. Where the population needs knocking down, University of Maryland Extension names Bacillus thuringiensis 'Kurstaki' and the insecticide spinosad as effective against the larvae.

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 worked from the pond he built himself. A still green surface broken by pink and white flowers reads as a picture before it reads as a plant. The giant Victoria carries leaves up to ten feet across, 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. Ribs radiate from the center of the leaf, and cross veins between them trap pockets of air that spread the load over the whole pad.

1. If a China mark moth has found your pond, variety choice becomes a control. It passes over Nymphoides cristatum 'White Snowflake' and Nymphaea 'Mrs. C.W. Thomas', so a chewed-out pot is a chance to replant.
2. 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 margin keeps supplying them.
3. Wild plants are no guide to how deep to sink a pot. Fragrant water lily roots in sediment under six to seven feet of water, on stalk length a potted cultivar does not have to spare.

Related Guides & Flowers

Peace lily

Another plant carrying the lily name without being one, and it lives indoors in a pot.

Pink flowers

Where the pink hardy cultivars sit among the other pink flowers worth planting.

Types of flowers

The full catalog of flowers on the site, grouped by type.

Passionflower

Another flower built on an unusual arrangement of parts that repays a close look.