Waterlilies are considered by most gardeners to be the most important plants in the garden pond. Certainly from the point of view of a floral display they are essential, but they also contribute to the general well-being of the pond environment. Their floating foliage shades the surface of the water providing welcome shade for the fish on a hot summer day. By reducing the amount of light that falls directly into the water, they also help to control green water discoloring algae. This requires full light in order to prosper.

There are two main groups of waterlilies. The hardy kinds that are all day-blooming and frost-hardy, and the tropical species and varieties which are frost-tender and available as either day or night blooming. There are innumerable shapes and sizes, with varieties that can be grown in as little as 6-8ins of water in a small container, to giants of the lake that require 6 feet of water in order to prosper. Waterlilies have a leafy spread of from as little as 9ins to as much as 15-18 feet.

Amongst the hardy kinds there are flowers of almost every hue except blue. This color is the sole prerogative of the tropical waterlilies. Some flowers are star-shaped, others cup-shaped and a number are fully double and of similar appearance to a fall-flowering chrysanthemum. A few have blossoms of a strong vanilla or aniseed scent while others are totally devoid of fragrance.

The leaves also vary in shape and size, but most are plain green, or else are green and have chocolate or maroon mottling. Hardy waterlilies grow mostly from a fleshy creeping and spreading rootstock, whereas tropical waterlilies arise mostly from rounded tubers, not unlike large chestnuts or small potatoes.

Hardy waterlilies produce "eyes" or latent shoots that are used for propagation purposes. Tropical kinds on the other hand, multiply from small tubers, or sometimes viviparously - small plantlets appearing from their leaves. These can be readily used from propagation purposes. Seed is not a common form of reproduction amongst hardy waterlilies, except in the case of the tiny pygmy species Nymphaea tetragona. However some tropical kinds are freely reproduced from seed.

Waterlilies are planted during spring and summer, the earlier in the season the better, for then they quickly establish and produce something of a show the first year. They must be grown in full sun in still water. Plant in a proper latticework-sided planting basket in a heavy loam soil with no additional fertilizer added, or else an aquatic planting compost. Before placing in the pond top-dress the compost with fine well-washed gravel. This helps to prevent the soil from dispersing into the water and also dissuades the fish from stirring up the mud in their quest for aquatic insect life.

Waterlilies require little attention, except for feeding with a slow release aquatic plant fertilizer. This is available in either tablet or sachet form and pushed into the compost mix next to each plant during the summer.