Waterlilies are exotic-looking beauties with their big, floating leaves and waxy, star- or cup-shaped flowers in gorgeous colors.

The genus name Nymphaea honors the nymphs of Greek mythology, minor female divinities occupying places in nature such as rivers, lakes, springs and seas. Waterlilies have been grown since ancient times, with depictions of Middle Eastern waterlily flowers (probably N. caerulea or N. lotus) in Egyptian hieroglyphics dated to around 2800 BC.

There are more than 150 species of waterlily in the world. A few are hardy, e.g. Nymphaea odorata from North America the Caribbean and Mexico; Nymphaea candida, native to Russia, China, India and Europe; Nymphaea pygmaea, a diminutive species native to China, Japan and Vietnam; and Nymphaea alba, native to Europe, India, the Mideast and elsewhere. But most waterlilies are indigenous to tropical countries and are tender plants in cold climates.

Compared to hardy waterlilies, tropicals tend to have more colourful flowers and larger leaves that are often splashed and mottled with darker color. They include some that bloom at night and some that are “viviparous”, meaning they asexually produce young plantlets from the point at which the stem attaches to the leaf.

Hardy waterlilies have been crossed with tender tropicals to give the best of both worlds: beautiful color and cold-hardiness. The first successful, hardy hybrids were bred in the late 19^th –early 20^th century by a French nurseryman, Joseph Latour-Marliac. More than a century later, much of his work has been lost but there are a few of his handsome progeny still popular . Excellent Marliac hybrids include ‘Marliacea Chromatella’ (1887), a lovely soft-yellow; ‘Marliacea Carnea’ (1887) with flesh-pink blossoms; ‘Gloriosa’ (1896), with large red flowers; ‘Gonerre’ (1914), with snow-white, cup-shaped flowers; and ‘Comanche’ (1908), a large waterlily with flowers that age from apricot-yellow to deep bronze-orange.

What Waterlilies Need

In order to produce their magnificent blossoms, waterlilies need warm water (cold water can stunt their growth) and a minimum of 5-6 hours of sun each day. Naturally, hardy hybrids can tolerate slightly cooler conditions than their tropical cousins; they can generally be planted in mid-spring when water temperatures have warmed to 60F (15C). For tropicals, it’s important to wait until water temperatures have warmed to 20C (70F); this might not happen until June, depending on the weather. However, tropicals will often bloom into late September or even early October, provided pond water is still warm enough while hardy waterlilies have usually entered dormancy by then.

Waterlilies need mineral-rich, fertile soil that is often described as “heavy”; this means a clay-loam soil that has the dense, sticky consistency that we would normally try to lighten, were it in a garden border. If you don’t have clay-loam soil, use a good quality topsoil. Avoid peat-based soilless mix (which will just float away) and triple-mix containing manure, which can cause an algae bloom. The plants are heavy feeders and will need fertilizer tablets especially formulated for aquatic plants, either a slow-release type that will last the season or one which will be applied regular through the summer. The tablets are pushed down well into the soil near the root zone.

How To Plant a Waterlily

You can buy your waterlily as a bare root plant from a mail order supplier, or you can buy it from a garden center or a specialist aquatic nursery, possibly already planted in the correct soil in a pond-ready pot or in an aquatic plant basket made with a porous plastic featuring small holes through which roots can permeate. Use newspaper to line porous pots, if you like, to keep soil in initially but allow the roots to poke through later as the newsprint breaks down.

· If you buy a bare root plant, or if it’s from a garden center but in an inappropriate container, transplant it into a large tub, plastic dishpan or plastic aquatic basket. The size will depend on the mature size of the waterlily, but a half-bushel (4 imperial gallons) is a minimum volume to allow for root growth (by measurement approximately 15 inches (38 cm) in diameter by 10 inches (25 cm) deep. If you buy your waterlily pre-planted, you merely need to add fertilizer tablets and submerge it in the pond.

· Fill the container half-full with soil and water it well. This will compact it and keep it from floating away once it is submerged.

· Carefully spread out the roots of the waterlily and place the rhizome atop the soil so the crown sits above the soil surface. Placement of the rhizome depends on the type of waterlily. Tropicals should be planted almost vertically. Hardy rhizomes should be planted horizontally at a slight angle, with the bud eyes facing up, the cut end against the container wall, and the growing end facing the center, enabling it to grow across the width of the pot during the summer. Continue to cover the roots with soil, distributing it around, but not covering, the crown.

· Water once more, ensuring again that the crown is not covered. Fertilizer tablets can now be pushed well down into the soil. Cover the soil surface with a ½ to ¾ inch layer of pea gravel; this will prevent the soil from floating out of the basket and keep it away from the rhizome crown.

· Place in the pond. Waterlilies need calm water to produce flowers; that means keeping them away from the splash of a fountain or waterfall. Tropicals like about 6-8 inches (15-20 cm) of water over their crowns (water near the surface is warmer, something that tropicals like). Hardy waterlilies prefer to grow deeper, with about 8-12 inches (20-30 cm) over the crown. If your pond is too deep, use blocks or bricks to achieve the right depth.

Winter Care

Depending on the depth of the pond, hardy waterlilies may or may not need removal to a frost-free place. If they can be moved into a deep part where the water does not freeze (3-6 feet, depending on the local frost line), they will be fine until spring. If not, they should be stored in a garage or basement room that stays cool (40-50F or 5-10C). Water the soil periodically through winter. Divide the rhizome in spring if the pot is too crowded.

Tropicals are not as easy to over-winter, and many gardeners treat them as annuals. Alternatively, the ideal is to move them into a greenhouse pond until spring. If that is not possible and you want to try to save them through winter, bring the pot to a cool room, remove the rhizome, clean it with water and let it sit for a few days before removing the foliage. Separate the old rhizome from any newly-formed ones and store the new ones in damp sand in a covered container – or in a jar filled with distilled water -- at 55F or 13C. Reserved rhizomes may or may not be viable in spring. If they’ve sprouted, place them in a small pot filled with appropriate soil about 4 weeks before the pond water will be warm enough (70F). Place them in warm water in full sun and grow them on until they’re ready for the pond.

For more on pond-building and general water gardening, read Water, Water Everywhere.

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