If you've installed a pond in your backyard, water lilies provide an attractive aquatic plant. While water lilies appear to float on the surface of the pond, they are actually planted in containers and submerged in your pond. To make the lilies appear to float, plant them yourself and then move them into the pond. Water lilies come either as tubers or as container plants; either can work as a pond plant.
Select a shallow, wide container for your water lilies, using one container per plant. Garden Ideas recommends a container that's 6 to 10 inches deep and 12 to 18 inches wide for each water lily tuber. Choose a container without drainage holes so that soil doesn't leak out into the pond.
Fill your container two-thirds of the way with potting soil. Place a water lily tuber in the pot so that its eyes point downward, toward the bottom of the container, and the tuber is slanted slightly at a 10 or 20 degree angle.
If you're planting a water lily transplant, plant it in the center of your pot and angle the root ball slightly.
Fill in the rest of the pot with soil. Then cover the top of the soil with 1/2 to 3/4 inch of gravel to prevent the soil from escaping into the pond water and clouding the pond water.
Water the newly planted water lily until the soil becomes moist.
Lower the container into the pond. The University of Illinois recommends placing aquatic plants in the water so that 12 to 18 inches of water cover the top of the pot, but advises working up to this gradually. Situate a container with a tuber only 6 inches submerged, then move the container toward the ideal depth as the plant grows. The plant needs light to grow, and the shallow water depth provides greater light.