Water lilies (Nymphaea) are beautiful aquatic plants that bloom in large, bright-colored flowers. Water lilies also have large, leathery leaves that float on the water surface. Water lilies serve several purposes in ponds. Aside from adding beauty to ponds, water lilies also provide shade to keep the water temperature cooler during the hot summer and to control algae growth. These aquatic plants also provide hiding places for fish and filter the water. Two main types of water lilies exist: hardy water lilies and tropical water lilies.
Position your water lily in a spot in your pond that receives full, direct sunlight. Ensure that the entire root system of the water lily is submerged in the water, with the leaves and flower resting on the water surface.
Maintain pond water temperatures warmer than 70 degrees Fahrenheit and no colder. Tropical water lilies are especially sensitive to cold water temperatures and shouldn't be exposed to water colder than 69 degrees. Hardy water lilies can tolerate much cooler water temperatures and bloom in water that's 60 degrees or warmer.
Feed your water lily once each month in May through August with an all-purpose, low-dosage aquatic plant fertilizer. Insert the fertilizer tablets in the potting soil to a depth of 2 to 3 inches, following the dosage instructions on the label.
Prune away any old or dead leaves from your water lily during spring. This will prevent the leaves from falling off the water lily and sinking to the bottom of the pond.
Bring your tropical water lilies indoors before the first frost and trim back their foliage. You can keep the tropical water lilies in the pond year-round if you live in a region that doesn't experience winter frosts.
Trim back all the dead leaves and stems from your hardy water lilies after the first hard frost. Sink the hardy water lilies into the deepest part of the pond for the winter.