These aquatic perennials grow with their roots in submerged soil and their long-stalked leaves floating on the surface. Floating leaves are rounded, with deep notch at one side where leafstalk is attached. Showy flowers either float on surface or stand above it on stiff stalks. There are hardy and tropical kinds. Hardy types come in white, yellow, copper, pink, and red. Tropical types add blue and purple to the color range, as well as an unusual greenish blue. Some tropicals in the white-pink-red color range are night bloomers; all others close at night. Many are fragrant.
Hardy kinds. These are easiest for beginners. Plant them from February to October in mild-winter areas, from April to July in cold-winter regions. Set 6-in.-long pieces of rhizome on soil at pool bottom or in boxes (not redwood ones, since these can discolor the water), placing rhizome in a nearly horizontal position with its bud end up. In either case, top of soil should be 812 in. below surface of water. Feed at planting time and monthly thereafter, using a controlled-release product. Groom plants by removing spent leaves and blossoms. They usually bloom throughout warm weather and go dormant in fall, reappearing in spring. In very cold areas, protect plants by covering the pond or by adding more water to it.
Tropical kinds. These begin to grow and bloom later in summer but last longer, often until the first frost. Buy started tropical plants and set them at the same depth as hardy rhizomes. Tropical types go dormant but do not survive really low winter temperatures. Their best chance of long-term survival is in regions where orange trees grow. Where winters are colder, store dormant tubers in damp sand indoors over winter or buy new plants each year.