30 June 2008
Virginia Cooperative Extension, Charlottesville/Albemarle County Office
460 Stagecoach Road, Charlottesville, Virginia 22902
phone: 434.872.4580 fax: 434.872.4578
Daylilies are one of the most used and well-liked perennials. They are easy to grow, provide blooms over a fairly lengthy period, and they are relatively maintenance free. Daylilies are not true lilies. They belong to the genus Hemerocallis, from the Greek words meaning "day" and "beauty" or "beautiful for a day." This is appropriate because each blossom typically lasts no more than a day. Each plant produces an abundance of buds, however, so the total blooming time of a well-established clump may be 30 to 40 days. By selecting early, mid-, and late-season varieties, it is possible to extend the flowering season from May until September.
Daylilies are grown both for their foliage that makes an excellent ground cover and for their attractive flowers that vary in form and color. Petal shapes may be wide, slightly recurved, overlapping, crinkled, frilled, and ruffled. The general flower shapes vary from trumpet- and cup-like to those resembling bells. Daylilies occur in a wide assortment of colors including white, yellow, orange, pink, red, and purple with a range within each color category. There are midget, dwarf, intermediate, and tall forms; thus height may range from one to four feet.
Daylilies are tolerant of drought and flooding; immune to heat stress; tolerant of most soils, full sun, or light shade; and they do not require fertilizer. Daylilies grow best in direct sun or light shade. They perform best with six hours or more of full sun daily. A slightly acidic (pH 6 to 6.5) garden soil with good drainage and organic matter is preferred. Planting may be done between April and September. Spacing generally is two to three feet between each plant (15 to 18 inches between miniatures). Keep plants evenly moist, but not constantly wet. Water should be thoroughly applied following planting until the plants are established. Consistent watering during the flowering period encourages high-quality flowers. A drip-irrigation system is ideal for daylilies. Daylilies usually grow well without fertilizer applications. However, if a soil test indicates the need for fertilizer, apply it in early spring. Avoid fertilizers containing too much nitrogen because excess nitrogen encourages flowers with extremely tall stems that break easily. Mulch is not necessary, but helps to conserve moisture in the soil and control weeds.
Daylilies have a few pest problems. They are prone to slugs, but this can be prevented by the use of slug bait and removal of their daytime hiding places by removing mulch and leaf litter near the base of the plant. Arthropod pests include aphids, spider mites, and thrips. These can be handled by natural enemies, by putting up yellow sticky cards nearby, and removing nearby weeds that serve as overwintering sites. Nematodes can cause some trouble as well. There are varieties less susceptible to nematodes if this is a problem. Diseases include leaf streak, soft rot, and the dreaded rust fungus.
Daylilies are fibrous-rooted, hardy perennials that require a cold-induced period in order to flower the following year. Daylilies can be divided into three categories based on their foliage habits: 1) Dormant types - the plant dies back to the ground following the first hard frost in autumn and grows new foliage in the spring; 2) Semi-evergreen types - the foliage only dies back partially and resumes growth in the spring; and 3) Evergreen types - the foliage is retained year round. In general, evergreen types can only be grown in the South and dormant types in the North. Virginia is capable of supporting all three categories.
There are also three categories of daylily blooming times: 1) Diurnal types bloom in early morning and last until the evening; 2) Nocturnal types bloom in the late afternoon and stay open until the following morning; and 3) Extended types remain open for as long as 16 hours and bloom at sunrise or late afternoon.
Propagation of daylilies is done primarily by division following flowering, although they will tolerate division throughout the entire growing season. Prior to division, cut the foliage back to one-half its length to ease handling and reduce water loss. If you are going to replant in the same location, replenish the soil before planting with well-rotted compost and a fertilizer high in phosphorus for root development. In the actual division process, it is best to begin by digging around the daylily clump with a spade and gently lifting the clump from the ground. Excess soil should be removed by hand or by spraying the root system with water. At this point, the clump can be divided into sections or "fans." Each fan should be planted in a hole that is 24 to 30 inches wide at a depth so the crown is about 1/2 to 1 inch below the soil level. It helps to make a mound of soil in the center of the hole and plant each fan so its roots are spread at a downward angle in the shape of a teepee. Next, the hole is filled in, and the soil is firmed. Each plant is then watered thoroughly to encourage root growth.
Daylilies should be divided every three to six years. Divide the plants when the clumps become too dense, when there is an obvious decline in the quality and number of flowers, or when you want to introduce them to a new location. However, some varieties may grow well for many years without being divided.
For more information about this and other landscape topics contact your local Virginia Cooperative Extension office. The local Virginia Cooperative Extension office numbers are Albemarle 872-4580, Fluvanna 591-1950, Greene 985-5236, Louisa 540-967-3422, and Nelson 263-4035.