Digging and Dividing Agapanthus
Cut the foliage on your Lily of the Nile to a few inches above ground level.
Using a garden fork, gently loosen the soil around the plant. Be sure to avoid bringing the tines directly under the plant where it might cause damage. If your agapanthus have been planted correctly, the rhizomes should be about three inches deep in hot climates and up to eight inches deep in moderately cold climates. This is done to protect plants grown as perennials from being affected by mild frosts.
Holding the top of the plant with one hand and a long-handled trowel in the other, gently lift the cluster of rhizomes out of the loosened soil. Wash away the dirt with a garden hose.
Use a clean, sharp knife to divide the rhizome sections. Make sure that each section contains at least one strong sprout. Each cluster of roots or rhizomes can be divided only into as many new plants as there are sprouts or emerging stems.
Re-plant immediately in hot climates. In cold climates, allow the divided roots to dry out on newspapers for two or three days. Then line the bottom of a cardboard box with more newspapers. Add a layer of play sand; lay the rhizomes on the sand. Continue to layer as needed then spritz the top of the sand lightly with water. Cover with a layer of newspaper and seal and label the box. Store in a cool, dry place until planting time in early spring.