Daylilies, Hemerocallis spp. are hardy in U.S. Department of Agriculture plant hardiness zones 2 to 9. Like fine wine, they get better with age and like to be left alone. They grow in sunny spots in moist, well-drained soil. Cutting back daylilies doesn’t harm them but it helps make your garden look neater.
"Beautiful for a day" is the exact translation of the genus name Hemerocallis. It describes their lovely blooms that each last for only a day. If you could only have one plant, choose daylilies. There are cultivars for every season to keep your garden alive with lots of pretty yellow, red, orange and copper colored flowers. After the flowers have faded, cut off the flower stem close to the base of the plant.
By the end of the growing season, a heavy frost blackens the top growth of the daylilies so that they slump and fall to the ground. Cut off the dead foliage, leaving 6 to 7 inches of dead growth on each crown helps to keep the plants rooted during winter’s inevitable freezing and thawing cycles. Reliable snow cover or mulch keeps the dead foliage hidden from view until the daylilies resume growth next spring.
Unless you want to give a friend a piece of your daylily plant or it is outgrowing its allotted spot, there is no need to cut back or divide its roots. Like peonies, daylilies improve with age and are better left alone. To divide the plant first dig it up with a spade, but don’t be surprised at the size of its roots. With a sharp knife, or saw, cut down through the roots, taking off a piece. Replant the rest.
Daylilies are tough hardy perennials that tend to live on in old neglected gardens, even after less resilient plants have given up. It is the gardener’s decision whether to cut back the foliage and flower stems. Given the plants penchant for survival, the daylilies won’t care. There really is no need to cut back their foliage or remove faded flower stems. New growth just pushes its way up through the tangle next year.