Once commonly called ditch lilies for their habit of naturalizing along roadside culverts, daylilies (Hemerocallis sp.) are becoming popular in both commercial and home gardens for their tough nature, beautiful flowers and graceful foliage. In addition to the original deep orange or yellow blooms, daylilies are now available in reds, purples, pinks, peaches and vivid combinations. The gracefully arching daylily foliage will often die back in late fall, becoming straw-colored lumps as temperatures drop. Trimming daylilies for winter can keep your yard tidy and your plants healthy.
Remove spent blooms and scapes throughout the growing season. This encourages the daylily to produce a thick, healthy root rather than multiple seed pods. The healthy tuber will support the dormant daylily throughout late fall and winter and provide energy for spring growth.
Clear fallen leaves and other debris from around the plant by hand or by using a rake, giving careful attention to the daylily crown. If fallen leaves are allowed to remain, they may become habitat for slugs, beetles and other pests seeking protection in mild-winter areas. Thick debris also prevents good air circulation and encourages crown rot and other diseases. Rot and fungal diseases can be problematic during wet winters, although daylilies are resilient plants.
Lift dead daylily leaves upright with one hand and cut cleanly across the spent leaves, 1 to 2 inches from the plant crown. Use sharp shears to prevent ragged leaves from shredding during winter storms. For large plantings, a weed-eater may be used. However, some daylilies are evergreen and should not be cut back. If an actively growing daylily is beginning to look ragged, trim the leaves 6 to 10 inches above the ground to encourage new growth. Otherwise, avoid cutting down green leaves; this will eventually starve the plant. Give a growing daylily time to recover by trimming at least six weeks before the first fall frost.
Mulch around newly-cut daylilies to insulate crowns and tubers from the cold. A good layer of mulch, 3 inches thick, will also retain moisture in the soil and prevent the tuber from drying out over the winter. Do not cover the crown.
In cold-winter areas, leave the dead foliage on the plant to provide extra insulation. This will not harm the plant, and the dead leaves can be cut back in spring to prepare for new growth. Freezing temperatures will usually prevent any pest or disease problems.
If an evergreen daylily becomes unattractive, mask them with fall-blooming plants or perennials with interesting foliage.