Water lilies (Nymphaea) are aquatic flowering plants that form the visual centerpiece of many ponds. They require periodic maintenance to ensure vibrant blooms and healthy foliage. Transplanting, which involves repotting and division, is necessary every two to three years. This is because the rhizomes become pot-bound and nutrient-depleted, leading to diminished flowering and smaller foliage.
Determining the Right Time and Materials
The timing of the transplanting procedure influences the plant’s recovery and subsequent bloom cycle. The most favorable period is in late spring or early summer, just after the plant has broken its winter dormancy and new growth is appearing. This window allows the lily to establish new roots in fresh soil before the peak heat of summer, minimizing the shock of division.
Before lifting the plant, gather all necessary materials. You will need a new, larger container, ideally an aquatic basket or solid pot at least 14 inches in diameter. The planting medium should be heavy clay soil or a specialized aquatic planting mix, as standard potting mixes are too light and will float. A sharp, sterile cutting tool, such as a large knife or pruning shears, and slow-release aquatic fertilizer tablets are also required.
Step-by-Step Guide to Dividing and Repotting
The repotting process begins by carefully lifting the old container out of the pond. Once removed, take the entire root ball out of the old pot, and wash all the soil away from the rhizome structure. Inspecting the rhizome is crucial for identifying the healthy, firm growing tips, often called “eyes” or “crowns,” which are the points where new leaves and flowers emerge.
Use the sharp, sterile tool to cut the rhizome into sections. Discard the old, soft, or spent center portion that is no longer actively growing. Each new division must be a piece of firm, healthy rhizome roughly four to six inches long and contain at least one visible growing tip. Trim away any old, yellowed, or damaged foliage and roots to direct the plant’s energy toward new growth.
Repotting technique differs based on the water lily’s type (hardy or tropical). For hardy water lilies, which have a long, horizontal rhizome structure, fill the new pot halfway with the heavy soil mix. Lay the rhizome horizontally, with the cut end placed against the side of the container and the healthy growing tip pointing toward the center and slightly upward, ensuring the tip is just above the soil line.
Tropical water lilies grow vertically from a central crown. Their rhizome should be positioned vertically in the center of the pot, with the entire crown remaining above the soil surface. Regardless of the type, press fertilizer tablets into the soil near the roots at this stage, providing nutrients for the coming season.
Top the container with more soil, leaving a small space at the rim, and gently tamp the soil down to remove any trapped air pockets. Spread a final layer of clean pea gravel or small river stones, approximately a half-inch thick, over the soil surface. This gravel layer prevents the planting medium from floating out into the pond water and keeps fish from disturbing the newly planted rhizome.
Submerging and Initial Care
Gently lower the newly repotted water lily into the pond to avoid a sudden rush of water that could dislodge the soil and gravel. Initially, the container should be placed in a shallow area, where the soil surface is covered by only a few inches of water.
Keeping the division in shallow water temporarily ensures the water temperature is warmer around the crown, stimulating faster recovery and the emergence of new leaves. As the water lily produces new pads and begins to grow vigorously, the pot can be gradually moved to its final, deeper location in the pond. This transition should occur over a few weeks, allowing the plant to acclimate fully to the deeper pressure and cooler temperatures. Monitoring for new, healthy growth is the best indicator of a successful transplanting.