Water lilies are an iconic addition to any aquatic environment, transforming a pond surface with lush foliage and vibrant blooms. These plants contribute to the pond ecosystem by shading the water, which helps regulate temperature and reduce algae growth. Planting them in deep ponds requires specific preparation and technique for successful establishment. This involves selecting the appropriate hardy variety and meticulously preparing the container before addressing the logistical hurdle of submergence.
Selecting Lilies and Preparing Containers
Selecting a hardy water lily variety is the first step, as tropical types require warmer, shallower water to thrive. Large cultivars such as Nymphaea ‘Attraction’ or ‘Charles de Meurville’ are often suited for greater depths, sometimes tolerating up to five feet of water once mature. Always check the specific depth requirements for the chosen variety, as tolerance varies significantly among cultivars.
The container must be wide and sturdy to provide stability and room for the rhizome’s horizontal growth pattern. A container at least 14 to 16 inches in diameter is recommended, providing enough space to establish the root system before division is needed. Avoid mesh baskets for deep ponds, as the soil can leach out, clouding the water and depleting the plant’s nutrients.
The planting medium must be heavy and dense, ideally a clay-based garden loam or commercially available aquatic planting soil. Standard potting mix or compost should not be used, as their lighter density and high organic content will float and contaminate the pond water. Fill the container about three-quarters full with the heavy soil, pressing it down firmly to remove trapped air pockets.
After planting the rhizome, cap the soil surface with a one-inch layer of pea gravel or coarse sand. This prevents clay particles from washing out when the pot is submerged and deters fish, particularly koi, from disturbing the soil while foraging. The weight of the soil and gravel also contributes to the container’s stability on the pond floor.
Proper Rhizome Planting Technique
The orientation of the water lily rhizome within the prepared container is important for healthy growth. Hardy water lilies typically grow horizontally, so the rhizome should be positioned at a 45-degree angle, not vertically in the center. The cut or oldest end of the rhizome should be placed firmly against the side of the container.
The growing tip, or crown, is the point where new leaves and flowers will emerge, and it must face upward and inward toward the center of the pot. This placement allows the new growth to spread across the container’s surface. Ensure the crown remains at or slightly above the soil line and is not buried by the planting medium.
Burying the crown can lead to rot and inhibit the plant’s ability to sprout new shoots. The rest of the rhizome should be covered just enough to anchor it securely in the heavy soil. Once positioned, gently firm the soil around the rhizome, taking care not to damage the growing tip.
Methods for Safe Submergence in Deep Ponds
Lowering a heavy, newly planted container safely into a deep pond requires a controlled approach to prevent the soil from dislodging or the pot from tipping. One effective method involves a harness system using strong rope or chain attached to the container’s handles or looped around its base. This allows you to slowly and steadily guide the pot to the pond floor from the edge.
Gently tilt the pot as you begin the descent, allowing air trapped in the soil to escape slowly. Rushing this process can cause a sudden rush of bubbles that dislodge the gravel cap and cloud the water. Once the pot reaches the bottom, the harness can be retrieved, leaving the planted lily undisturbed.
Another method, beneficial for establishing new or young plants, involves gradual submersion. Newly planted lilies should initially be placed in a shallower section of the pond, with only 6 to 12 inches of water covering the crown. As the leaf pads grow and reach the surface, you can progressively lower the container deeper over several weeks.
This gradual adjustment ensures the plant does not expend too much energy stretching its stems to reach the light, a common stressor in deep water. You can utilize submerged platforms, cinder blocks, or aquatic shelving to create temporary, adjustable depths. Moving the pot to its final, deeper location should only occur once the plant has demonstrated vigorous growth and established a full canopy of surface leaves.
Post-Planting Fertilization and Depth Adjustment
Water lilies are heavy feeders and require supplemental nutrients to support robust leaf production and continuous flowering. Long-term care involves regular fertilization using specialized slow-release aquatic fertilizer tabs. These tabs provide a steady supply of nutrients without dissolving immediately into the water column.
The fertilizer tabs should be pushed deep into the soil medium, placed near the edge of the container and away from the rhizome. Placing them too close to the growing tip can cause chemical burn, potentially damaging the new growth. Fertilization is recommended every four to six weeks during the active growing season.
Seasonal depth adjustments are necessary for the plant’s health, especially in colder climates. In early spring, raising the container closer to the surface can warm the water around the rhizome, stimulating earlier growth. Conversely, for winter dormancy, the pot should be lowered to the deepest part of the pond, typically below the freeze line, to protect the rhizome from ice formation.