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Missouri Environment & Garden


David Trinklein
University of Missouri
Plant Science & Technology
(573) 882-9631

Daylily: America's Favorite Perennial

David Trinklein
University of Missouri
(573) 882-9631

Published: June 13, 2012

Few garden flowers give so much pleasure while "asking" for so little as does daylily. In the quest most gardeners pursue for a "no maintenance" plant, daylily is about as close as one can get. Indeed, it often is mused that "daylilies thrive on neglect". Couple their ease of care with the myriad of flower colors, types and sizes available and it is little wonder why daylily is America's most popular perennial flowering plant. June is the month most daylily cultivars are at their best and a great time to enjoy this colorful, carefree plant.

Daylily belongs to the genus Hemerocallis. The latter is derived from the Greek words hemera (day) and kalos (beautiful), and makes reference to the fact that the showy flowers of this plant rarely last for more than 24 hours. Taxonomic authorities recognize 18 separate species of Hemerocallis. Unlike other members of the Liliaceae (lily) family daylily does not grow from a bulb. Instead, it produces fleshy roots that serve as a repository for food reserves. Daylily is a clump-forming plant with strap-like leaves that vary in size according to cultivar. Its flowers are perfect and in parts of three, as is the case with most monocots.

Daylily is considered to be native to China, Japan and Korea. The first written record of daylily dates back to 2697 B.C. and indicates Chinese ancients used it as a source of food and for its perceived medicinal properties. The latter included using daylily to solve a range of problems from relieving pain to uplifting the spirit. Indeed, in Chinese literature the word for daylily and "forget-worry" are synonymous.

Later, daylily was taken to Asia Minor where, in 70 A.D., the Greek herbalist Dioscorides made reference to a species of Hemerocallis that still is grown today. Over the years, daylily continued to be touted for its medicinal properties and was mentioned in several European herbals in the 16th century under a variety of (now-obscure) names such as Lilium non-bulbosum. Daylily was assigned its current botanical name in 1753 by the Swedish naturalist Linnaeus.

By the late 1800's many daylily species could be found in American gardens. However, it was the work of geneticists and plant breeder Dr. Arlow B. Stout that started daylily on the path to the popularity it enjoys today. Dr. Stout, considered to be the father of the modern daylily, received plants and seeds from China in 1924 and began a program of breeding and improvement. His work not only resulted in the development of hybrid daylily cultivars but also produced an understanding of the genetics of the genus Hemerocallis. The work of Dr. Stout did much to encourage both professional and amateur plant breeders to hybridize daylily. Their efforts have resulted in an astounding 72,092 daylily cultivars registered by the American Hemerocallis Society according to its 2011 database.

Such a multitude of cultivars requires the use of a sizeable glossary when attempting to describe daylily flowers and distinguish one cultivar from another. Terms such as single, double, spider, circular, flat, informal, triangular, star and recurved are examples of a few of the many terms used to describe flower form. Additionally, flower color and/or pattern are described by terms such as self, blend, polychrome, bi-tone, bicolour, watermark and eye zone. A complete listing of terms associated with daylily can be found at the following web address: http://www.daylilies.org/ahs_dictionary/dictionary.html.

Although it has been said that daylilies thrive on neglect, the fact is that proper care will produce more robust and attractive plants and flowers. Daylily is a full-sun plant and should be located where a minimum of six to eight hours of direct sun is received daily. However, a bit of late afternoon shade does help to preserve flower color and longevity. In shady exposures abundant foliage but very few flowers are produced.

Daylily prefers a medium-heavy garden loam, although it can tolerate a wide array of soil textures. Soil of any texture should be improved by incorporating liberal amounts of organic matter in the form of well-rotted manure, compost or peat moss before planting. Good soil drainage is important for optimum growth and performance; however, daylily will survive in extremely dry or excessively moist conditions. Plants growing in the latter easily succumb during severe winters even though the same conditions are tolerated during the summer.

Like any plant, daylily requires nutrients but additional fertilizer should be applied sparingly since too much nitrogen can be detrimental. Daylilies growing in very rich soils require little (if any) additional fertilizer. In average garden loams the application of a complete fertilizer such as 5-10-5 in the spring of the year when new growth starts usually is adequate. In extremely poor soils or soils that leach easily, a follow-up application of fertilizer might be warranted. When applying fertilizer, avoid spreading it on the leaves of the plant. This can lead to the accumulation of fertilizer at the base of the leaf and result in tissue burn when the fertilizer is wetted. Soil pH should be maintained around 6.5 for optimum nutrient availability.

As previously stated, daylily is fairly drought-tolerant. However, adequate amounts of water result in an increase in both flower number and size. Water especially is important in the spring when the plants are forming scapes and setting buds and, later, when plants are in bloom. Thorough (deep) watering that penetrates eight to ten inches into the soil is preferred over frequent, light watering. Overhead watering during the day can cause open flowers to spot and wilt. Therefore, if applied overhead, watering early in the morning is best.

Daylily is subject to attack by a variety of pests and diseases but most do only minor damage. Aphids, thrips and spider mites are the most common insect pests. Crown and root rot, leaf streak and daylily rust are diseases that can be problematic. Proper sanitation including the removal of garden debris at the end of the growing season can help to prevent pest problems.

Weeds can be controlled through the use of mulches which also to preserve soil moisture. If organic mulches are use the improvement of soil structure is an added benefit.

As do most clump-forming perennials, daylilies require periodic division for best garden performance. The frequency of division depends largely on cultivar and growing conditions. Cultivars known for their reblooming tendency such as 'Stella de Oro' should be divided relatively frequently. This helps to force new growth throughout the growing season which is the primary factor that causes a daylily to rebloom. Daylilies can be divided (or planted) any time the ground is not frozen; however, late August through September is the most ideal time.

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REVISED: June 13, 2012