Water lilies (Nymphaea) depend on the aquatic environment they inhabit. “Watering” a water lily means managing a small-scale ecosystem. These aquatic plants require specific parameters of depth, quality, and temperature to thrive and produce their signature flowers. Successful cultivation involves maintaining a stable and clean aquatic habitat.
Establishing the Proper Water Depth and Environment
Hardy water lilies typically thrive when placed so the crown of the plant is submerged 18 to 24 inches below the water surface, though this range can vary based on the specific cultivar size. Smaller or dwarf hardy varieties may only require 12 to 18 inches of depth, while larger types can handle up to four feet. Maintaining the proper depth is important because it regulates the temperature of the substrate, protecting the rhizomes from overheating in direct, intense sunlight.
Tropical water lilies, by contrast, generally prefer a slightly shallower placement, thriving with 12 to 24 inches of water above the planting container. When initially planting, it is often necessary to place the container on bricks or a submerged shelf to keep the crown closer to the surface, especially for young plants. As the plant grows and produces longer leaf stems, blocks can be removed incrementally to lower the container to its final, optimal depth. This gradual lowering ensures the leaves are not overly stretched trying to reach the water surface, which can stress the plant.
Maintaining Water Quality and Temperature
Water quality is a direct factor in the overall health of the aquatic environment and the water lily itself. Water lilies generally prefer a neutral to slightly acidic pH range. If using municipal tap water, which often contains chlorine or chloramine, it should be treated to remove these chemicals, either by using a commercial dechlorinator or by allowing the water to sit exposed to the air for at least 24 hours to allow chlorine to dissipate.
Water temperature is a significant factor, determining when a plant will begin active growth and bloom. Hardy water lilies start to grow when temperatures are around 60°F, while tropical varieties require the water to be above 70°F for optimal blooming. Rapid temperature fluctuations can shock the plant, which is why sufficient water depth helps stabilize the thermal environment. Any water lost to evaporation must be replenished regularly using aged or treated water to maintain the established depth.
Seasonal Water Management
Managing the water level through the summer is a continuous task, primarily due to evaporation. It is important to top off the pond or container slowly with treated water to avoid shocking the plant’s roots with a sudden influx of colder water. Consistent replenishment ensures the water level remains within the target depth range.
Winter preparation differs significantly between the two types of water lilies. Hardy water lilies require no special protection if they are planted deep enough in a pond that the rhizome is below the frost line. If the planting container is in a shallow pond that might freeze solid, the entire container should be moved to the deepest part of the pond or stored in a cool, dark location, such as a basement, where the temperature stays above freezing (around 40 to 50°F).
Tropical water lilies cannot tolerate freezing temperatures and must be brought indoors in colder climates. One method involves inducing dormancy by removing the tubers after the first frost, cleaning them, and storing them in damp sand or peat moss at temperatures above 50°F. Alternatively, the entire potted plant can be moved into an indoor aquarium or tank with water kept above 60°F, where it can continue to grow slowly under supplemental light until spring.