Many aquatic plants grow from rhizomes or roots planted deep in the bottom of pond dirt or muck. In the garden pond, landscapers anchor these roots and rhizomes in clay containers or baskets filled with soil. Part of the work of cleaning a pond in spring involves splitting the roots of overcrowded plants or separating rhizomes that naturally replicate through division. Doing so can help overcrowding in ponds and make your plants healthier.
Time plant division for early spring when the weather is still cool and plants are dormant. Plants divided while dormant are less prone to shock from the division.
Remove the plant from the pot and rinse off the roots or rhizomes.
Cut the root ball or rhizome in two to four pieces. Cut water lilies along the natural breaks between the rhizome of the plant.
Fill a plastic aquatic net basket two-thirds full of a soil formulated for aquatic plants.
Place the root ball in the center of the basket.
Fill in around the sides of the plant with soil until the soil line is 1 inch from the top of the container.
Top off the soil with coarse sand. The sand will anchor the soil into the basket.
Water the container and place it back into the pond. Discard, give away or repot the remaining divisions of the plant.