Day lilies (Hemerocallis spp.) welcome summer with a burst of color. Each plant sends up several stems, each adorned with many blooms. Day lilies grow in U.S. Department of Agriculture plant hardiness zones 3 through 10. Most day lilies flower over a period of several months, so summer flowering often lasts into fall. Depending on the variety, day lilies may go dormant in winter or the foliage may remain evergreen. Cutting down the plants correctly helps clean up the bed and ensures the plants survive the winter and return next year.
Cut back each flowering stem as the last bloom wilts throughout summer. Remove the stalks at their base, cutting through them with shears or a knife.
Trim back the foliage on deciduous day lilies as the leaves die back naturally in fall or early winter. Remove each leaf near its base as it yellows, or wait for all the leaves to die back and prune them off all at once.
Prune out dead leaves, whenever you see them, from evergreen day lily varieties. Cut out dead, yellowed or damaged leaves at the base where they emerge from the main plant. Avoid cutting out any healthy green foliage.
Spread 2 inches of fresh mulch over the day lily bed after cutting back the dead foliage in fall, or after the first frost if you grow evergreen day lilies. The mulch insulates the soil and protects the roots of the day lilies from winter temperature fluctuations.