Although spring is the easiest time to divide your hardy water lilies, they can be divided anytime during the growing season. After a year or two, your water lilies will become pot-bound and need dividing and repotting. This is a great time to start a few more plants for your pond or share your favorite variety with friends.
Step One
Remove the pot from the water lily. Using a garden hose, gently wash away the soil to expose the root system.
Step Two
Examine the tuber. You will see older growth on one end and newer growth (buds, leaves, roots) on the other end. You can simply snap off and discard a large portion of the old section of the tuber. Growing "eyes" may have formed along the tuber. These may be cut off and potted.
Step Three
Using a knife, cut back the tuber on the growing portion of the plant. Smaller varieties, like Perry's Baby Red, can be cut to two inches in length. Larger varieties, like Joey Tomocik, need a five-inch tuber. Many commercial growers trim off all the roots except the emerging new (white) roots. Cut off all new buds and the older leaves. This helps balance the new plant's energy budget. The plant needs to put most of its effort in developing a new root system, not making leaves and flowers.
The older portion of the tuber has been removed.
Step Four
Plant the tuber in good garden soil, not commercial potting soil. If there are large holes in the pot, add a layer of burlap or newspaper before adding the soil. Push the cut end of the tuber down into the soil, next to the pot wall. This provides the most room for the new roots to spread out in the soil. Place two Aquatic Plant Food Tablets halfway into the soil. Press the soil around the tuber to keep it in place when submerged under water. Next, place a layer of pea gravel over the soil. Pea gravel holds the soil in place and prevents fish from digging in the pots. Do not cover the crown (the growing tip of the tuber).
Fill the pot with heavy garden soil. Don't forget to add two Aquatic Plant Food Tablets.
Step Five
Gently submerge the pot into the pond. Some soil will become suspended in the water but will quickly settle out. Newly potted water lilies should be kept in shallow water (up to 12" deep) until five or six new leaves appear. After that, the plants may be lowered into deeper water.
Gently lower the pot into the pond.