Water Lilies
Like marginals, water lilies grow with their roots and stems in soil below the water surface, but their foliage --round leaves that look like green platters--floats on the water. Some cultivars also have floating flowers; others hold their blooms on stems several inches out of the water. Most water lilies grow in 3 to 4 foot depths, some in depths up to 8 feet, but they do quite well in ponds with only 6 to 18 inches of water over their roots. They provide shade and cover for fish, as well as an egg-laying platform for certain species of dragonflies whose larvae feed on insects.
Water lilies are classified into two broad groups. Hardy water lilies survive winters in cold climates. Tropical water lilies cannot withstand a winter freeze and need special care during cold months. To tell if a water lily is hardy or tropical, look at the edge of its rounded leaves. If the edge is smooth, the lily is hardy. If the edge is crinkled, wavy, or toothed, the lily is tropical.