Water lilies are the final frontier of the gardening world, says University of Missouri Extension horticulturist David Trinklein.

Many admire them. Few grow them.
Water lilies are the final frontier of the gardening world, says University of Missouri Extension horticulturist David Trinklein. While they may appear exotic and fragile, water lilies are tough and durable, Trinklein said. Many gardeners think they’re difficult to grow, but Trinklein says that is not the case. “Once established, water lilies flower well into the summer and provide an exotic addition to any landscape.”
Neophyte gardeners might want to think small when starting a water lily garden. Large pools with fountains and waterfalls are impressive but more challenging, Trinklein said. Small, preformed plastic pools or tubs are an easy way to grow lilies with success. The ubiquitous whiskey half-barrel planted with a dwarf water lily is an ideal way for beginners to gain experience with water lilies, he added.
To thrive, water lilies need abundant sunlight—at least six hours per day. As a rule, the more sunlight, the better, said Trinklein. Lilies need sunlight for growth and to warm cool water.
Tranquil waters suit them best. Fountains or other features that create turbulent waters reduce lilies’ performance, he says.
There are two basic types of water lilies: hardy and tropical. Hardy lilies grow from rhizomes and are day bloomers that close their blossoms each evening. Excellent choices for beginners, they can be left in pools that do not freeze solid. Water should be at least 24 inches deep.
Tropical lilies are considered showier by most. Some bloom during the day and others bloom from dusk through early morning the next day. Gardeners who commute to work for the day may enjoy lilies that bloom when they are home, Trinklein said. But that enjoyment does come at a price. Tropical water lilies are a bit more demanding.
Tropical water lilies grow from tubers and are not winter-hardy in Missouri. The tuber must be removed from the water garden every fall and stored inside for the winter in an environment in which it is kept constantly moist. For best results, plant tropical lilies mid-to-late June in Missouri, or after the water reaches 60 degrees Fahrenheit. Tropical lilies are available in many colors. Their elaborate flowers often are fragrant, making for a delightful evening walk through the garden, said Trinklein.
Do not crowd water lilies. Exposed water improves the appearance of the garden.
Plant them in heavy soil (not potting soil) in pots that are submerged in the pool. Avoid soil mixes with perlite, vermiculite or peat. These light mixes will float out of the pot. Carefully handle brittle rhizomes and tubers. Plant so that the crown is 10-12 inches below the water’s surface once the pot is submerged. Do not place on the bottom of the pool. Place dwarf varieties no more than 5 inches below the water’s surface.
Water lilies are heavy feeders. Aquatic plant fertilizer tablets that release nutrients slowly are available online and in garden supply stores. Use according to label directions.
Few diseases and pests affect water lilies. Dogs may harm them when taking a dip in a water garden. Turtles tend to eat their leaves and koi may nibble on their foliage.
Divide the rhizomes of hardy water lilies when they become crowded, quit blooming well and leaves push above the water. It usually takes four to five years for this to happen.