Daylilies are a hardy perennial that grows from a fibrous root system and not technically a bulb. Daylilies are popular for ground cover in areas such as slopes or foundation gardens, but even ground cover plants can benefit from division. Divide daylily clumps every three or four years to create new plants and promote healthy blooming.
Daylilies should be divided in early spring or immediately after blooming ends in late summer. Spring divisions are most common simply because foliage is not in place yet, which makes handling the clumps easier.
Dig around the outside of the root ball to release the plant without doing major damage to the root system. When the plant is loose, rock it free of the soil. Divide by pulling apart into "fans," small plants that consist of a crown, foliage and a separate root system. Throw away any woody or diseased fans.
Replant fans as soon as possible in well-draining, nutrient-rich soil or keep roots moist to trade or give to other gardeners. Divide every three or four years when bloom production starts to wane and plants seem crowded.