Loved by most, but grown by few, water lilies suffer from the perception they are difficult to grow. Such is not the case. The special conditions needed to allow these aquatic beauties to grace one's garden are not all that complex to provide. Once established, water lilies flower well into the summer and provide an exotic addition to any landscape.
Although large pools with fountains and waterfalls are impressive, beginners to water gardening would benefit by growing water lilies in a smaller space. Either a small, pre-formed pool or large tub set into the ground are good ways for neophytes to delve into water gardening. The edge of the pool or tub can easily be concealed with flat stones or plants. Pre-formed pools usually are made of plastic or fiberglass and should be set on sand to prevent damage which could result in leakage.
Water lilies need abundant sunlight to perform well. Therefore, water gardens should be located where they will receive a minimum of six hours of direct sunlight every day. Although water lilies will survive in less light, their flowering will be diminished. As a general rule, the more sunshine the better for water lilies.
Additionally, water lilies grow best in tranquil water warmed by the sun. Larger pools with features such as fountains or water falls that create turbulent water reduce water lily performance. Pools that might be replenished frequently with cool water are equally unsatisfactory.
There are two basic types of water lilies: hardy and tropical. Hardy water lilies produce rhizomes and are best suited for our geographic region. They may be left in the pool year-around if the water does not freeze solid. In Missouri, pools should be at least 24 inches in depth to assure the presence of free water below a top layer of ice. Shallow pools may be equipped with water heaters to prevent freezing, but this adds to the expense of ownership.
Tropical water lilies grow from tubers and are not winter hardy in Missouri. Therefore, they must be removed from the water garden every fall and stored for the winter indoors under moist conditions. They should not be planted until water in the pool is quite warm (65o F, or above). This often is mid- to late June at our latitude, resulting in a longer wait to enjoy water lily flowers in the landscape.
The flowers of tropical water lilies are often larger and more spectacular than the hardy types, although a great deal of progress has been made in improving the latter. However, tropical types hold their blooms well above the surface of the water and are available in a wide array of colors including shades of blue. Additionally, most tropical types are pleasantly fragrant.
Hardy water lilies are day blooming and most flowers close in late afternoon. On the other hand, tropical water lilies come in two types relative to blooming habit. Day bloomers, like the hardy types, open in mid-morning and remain open until late afternoon. Night bloomers open at dusk and remain open until mid-morning of the following day. This is an added benefit for gardeners who work away from home during the day and wish to enjoy their water garden in the evening.
Water lilies should not be crowded. If the pool or tub is small, plant only one or use dwarf varieties. Crowding water lilies not only reduces the number of blooms, but the abundant number of lily leaves may entirely cover the surface of the water. Exposed water not only makes the pool more attractive, it is necessary for good air exchange if fish are kept in the pool. If excessive foliage develops, it should be cut and removed. Always remove older leaves and stems first and allow about 40 percent of the water's surface to be exposed.
May is an ideal month to plant hardy water lilies. Do not plant water lilies directly on the bottom of the pool. This makes them more difficult to maintain. Instead, plant them in tubs or containers that are then submerged into the pool. For standard types, a container that holds about one cubic feet of soil is ideal. For dwarf varieties, a container 9 to 10 inches in diameter is adequate.
When planting, handle water lily rhizomes and tubers along with their roots carefully, since they are quite brittle. After the rhizome or tuber has been planted, the container should be placed into the pool so that the crown is 10 to 12 inches below the surface of the water. Dwarf varieties should be located so they are five inches below the water's surface. Blocks or bricks may be places under the container to position it properly.
Water lilies grow well in fairly heavy clay soils low in organic matter. They are, however, heavy feeders. Special fertilizer tablets formulated for water lilies are available at nurseries or garden centers that stock water garden supplies. Alternatively, they can be ordered online. Water lily tabs are made from slowly soluble materials that are not quickly released in water. Fertilizer tabs should be placed in the soil before placing the plants into the pool and, later, according to label directions.
Before the danger of frost in the fall, tropical varieties, as well as hardy types in shallow pools or tubs, should be removed from the water garden. During the winter, they should be kept moist and, in the case of the tropical types, relatively warm. The latter can be accomplished by removing the soil to expose the plant's roots and tuber. After dusting with a fungicide, place the roots/tuber in moist sand and maintain at 60o F. Alternatively, the entire plant and container can be brought indoors. After trimming back most of the leaves, place the container in a large aquarium or small plastic pool maintained at 60o F.
Water lilies are afflicted by very few diseases and pests. Dogs do not eat water lilies but often harm them when taking a dip in the water garden. Turtles tend to snack on lily foliage and produce scissors-like cuts in their leaves. Koi have been known to nibble on lily foliage as well.
Hardy (rhizomatous) water lilies should be divided when they become crowed in their container. Normally, it takes four or five years for this to occur, depending on the vigor of the plant. Key indicators that it is time to divide include reduced blooming or leaves pushing out above the surface of the water.
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REVISED: February 21, 2017