Because of the extensive root system, a sharp knife may be required. However, cutting the roots with a knife can cause more stress to the plant and should only be done if necessary. Alternatively, use a shovel to dig up the entire daylily clump. Remove the soil from the roots by shaking it or spraying the roots with water. Separate the plants into clumps of two or three. Cut the leaves to about half their height. This will enable the roots to better support the plant without falling over while also reducing the water lost through transpiration.
Replant the divided clumps at the same depth 24 to 36 inches apart. Flowering will be limited next year but will become more vigorous until it is time for dividing again. (Cynthia Domenghini)