|Hemerocallis 'Hush Little Baby'|
Daylily is the general nonscientific name of a species, hybrid or cultivar of the genus Hemerocallis (pron.: //). Daylily cultivar flowers are highly diverse in colour and form, as a result of hybridization efforts of gardening enthusiasts and professional horticulturalists. Thousands of registered cultivars are appreciated and studied by local and international Hemerocallis societies. Hemerocallis is now placed in family Xanthorrhoeaceae, subfamily Hemerocallidoideae, and formerly was part of Liliaceae (which includes true lilies).
Daylilies are perennial plants. The name Hemerocallis comes from the Greek words ἡμέρα (hēmera) "day" and καλός (kalos) "beautiful". This name alludes to the flowers which typically last no more than 24 hours. The flowers of most species open in early morning and wither during the following night, possibly replaced by another one on the same scape (flower stalk) the next day. Some species are night-blooming. Daylilies are not commonly used as cut flowers for formal flower arranging, yet they make good cut flowers otherwise as new flowers continue to open on cut stems over several days.
Hemerocallis is native to Eurasia, including China, Korea, and Japan, and this genus is popular worldwide because of the showy flowers and hardiness of many kinds. There are over 60,000 registered cultivars. Hundreds of cultivars have fragrant flowers, and more scented cultivars are appearing more frequently in northern hybridization programs. Some cultivars rebloom later in the season, particularly if their capsules, in which seeds are developing, are removed.
Most kinds of Daylilies occur as clumps, each of which has leaves, a crown, flowers, and roots. The long, linear lanceolate leaves are grouped into opposite fans with arching leaves. The crown is the small white portion between the leaves and the roots. Along the scape of some kinds of daylilies, small leafy "proliferations" form at nodes or in bracts. A proliferation forms roots when planted and is often an exact clone of its parent plant. Many kinds of daylilies have thickened roots in which they store food and water.
A normal, single daylily flower has three petals and three sepals, collectively called tepals, each with a midrib in the same or in a contrasting color. The centermost part of the flower, called the throat, usually has a different color than more distal areas of its tepals. Each flower usually has six stamens, each with a two-lobed anther. After successful pollination, a flower forms a capsule (often erroneously called a pod).
The Tawny or Fulvous Daylily is invasive in some parts of the United States, such as in Wisconsin (Wisconsin Department of Natural Resources). People sometimes plant the Fulvous Daylily and other stoloniferous daylilies, which have underground runners. These kinds can overrun one's garden and can take an appreciable amount of time and effort to confine or remove.
"The Perfect Perennial" 
The daylily is often called "the perfect perennial," due to its dazzlings colors, ability to tolerate drought, capability to thrive in many zones, and requiring very little care. Daylilies thrive in full sun, although certain daylilies require partial shade, depending on color. Lighter shades, such as yellow, pink, and pastels require the sun to bring out all of their color. Darker daylilies, such as some red and purple flowers, need shade because their darker colors absorb heat.
Today, daylilies come in an assortment of shades, whereas they formerly were only available in yellow, pink, fulvous, and rosy-fulvous. Now the flowers can be found in many shades of yellow, pink, red, purple, and melon. The only shades daylilies are not available in are pure blue and pure white, which hybridizers are working on.
Daylilies have a relatively short blooming period, depending on the type of daylily. There are a variety of different dayliles; some of which will bloom in early spring, while other wait until the summer or even fall. Most dayliles bloom for one to five weeks, although there is a type of daylily known as a rebloomer, which will bloom twice in one season. 
Depending on the species and cultivar, daylilies grow in USDA plant hardiness zones 1 through 11, making daylilies some of the more adaptable landscape plants. Hybridizers have developed the vast majority of cultivars within the last 100 years. The large-flowered, bright yellow Hemerocallis 'Hyperion', introduced in the 1920s, heralded a return to gardens of the once-dismissed daylily, and is still widely available in the nursery trade. Daylily breeding has been a specialty in the United States, where daylily heat- and drought-resistance made them garden standbys since the 1950s. New cultivars have sold for thousands of dollars, but sturdy and prolific introductions sell at reasonable prices of US$20 or less.
The Tawny Daylily (Hemerocallis fulva), and the sweet-scented Lemon-lily (H. lilioasphodelus; H. flava, old name) were early imports from England to 17th-century American gardens and soon escaped from gardens. The introduced Tawny Daylily is now common in many natural areas, and some people think that it is a native wildflower. Its nonscientific names include Railroad Daylily and Roadside Daylily, Ditch Lily, and Outhouse Lily, Tiger Lily, and Wash-house Lily (although it is not a true lily). Some people have planted this species near outhouses and wash houses, hence two of its nonscientific names.
Hemerocallis is one of the very highly hybridized plant genera. Hybridizers register hundreds of new cultivars yearly. Hybridizers have extended the genus' color range from the yellow, orange, and pale pink of the species, to vibrant reds, purples, lavenders, greenish tones, near-black, near-white, and more. However, hybridizers have not yet been able to produce a daylily with primarily blue flowers in forms of blue such as azure blue, cobalt blue, and sky blue. Flowers of some cultivars have small areas of cobalt blue.
Other flower traits that hybridizers developed include height, scent, ruffled edges, contrasting "eyes" in the center of a bloom, and an illusion of glitter which is called "diamond dust." Sought-after improvements include foliage color and variegation and plant disease resistance and the ability to form large, neat clumps. Hybridizers also seek to make less-hardy plants hardier in Canada and the Northern United States by crossing evergreen and semi-evergreen plants with those that become dormant and by using other methods. Many kinds of daylilies form clumps of crowded shoots. People dig up such kinds every 3 or so years, separate shoots, and replant only some of the shoots to reduce crowding. This process increases the flowering of many cultivars.
In the last several decades, many hybridizers have focused on breeding tetraploid plants, which tend to have sturdier scapes and tepals than diploids and some flower-color traits that are not found in diploids. Until this trend took root, nearly all daylilies were diploid. "Tets," as they are called by aficionados, have 44 chromosomes, while triploids have 33 chromosomes and diploids have 22 chromosomes per individual plant. Hemerocallis fulva 'Europa', H. fulva 'Kwanso', H. fulva 'Kwanso Variegata', H. fulva 'Kwanso Kaempfer', H. fulva var. maculata, H. fulva var. angustifolia, and H. fulva 'Flore Pleno' are all triplods that almost never produce seeds and reproduce almost solely by underground runners (stolons) and dividing groups by gardeners. A polymerous daylily flower is one with more than three sepals and more than three petals. Although some people synonymize “polymerous” with “double,” some polymerous flowers have over five times the normal number of petals.
|'Beloved returns'||'Green flutter||'Red precious'|
|'Berlin lemon'||'Helle Berlinerin'||'Royal Mountie'|
|'Berlin red'||'Lemon bells'||'Stoke Poges'|
|'Berlin red velvet'||H. lilioasphodelus||'Tetrina's Daughter'|
|'Burning daylight'||'Marion Vaughn'||'Whichford'|
|'Chief Sarcoxie'||'Neyron rose'|
|'Golden chimes'||'Pink damask'|
Culinary use 
The flowers of some species[which?] are edible and are used in Chinese cuisine. They are sold (fresh or dried) in Asian markets as gum jum or golden needles (金针 in Chinese; pinyin: jīn zhēn) or yellow flower vegetables (黃花菜 in Chinese; pinyin: huáng huā cài). They are used in hot and sour soup, daylily soup (金針花湯), Buddha's delight, and moo shu pork. The young green leaves and the rhizomes of some (but not all) species are also edible. The plant has also been used for medicinal purposes. Care must be used as some species of lilies can be toxic.
- Hemerocallis citrina Baroni (syn. H. altissima Stout, H. coreana Nakai)
- Hemerocallis darrowiana S.Y.Hu
- Hemerocallis dumortieri E.Morren
- Hemerocallis esculenta Koidz. (syn. H. pedicellata Nakai)
- Hemerocallis forrestii Diels
- Hemerocallis fulva (L.) L. (H. sempervirens Araki, H. sendaica Ohwi and H. aurantiaca Baker are now treated as varieties of this species) – Orange Daylily, Tawny Daylily, Tiger Lily, Ditch Lily
- Hemerocallis hakuunensis Nakai (syn. H. micrantha Nakai)
- Hemerocallis hongdoensis M.G.Chung & S.S.Kang
- Hemerocallis lilioasphodelus L. (syn. H. flava (L.) L.) – Lemon Lily, Yellow Daylily
- Hemerocallis littorea Makino
- Hemerocallis middendorffii Trautv. & C.A.Mey. (includes H. exaltata Stout as H. m. var. exaltata)
- Hemerocallis minor Mill. (syn. H. sulphurea Nakai)
- Hemerocallis multiflora Stout
- Hemerocallis plicata Stapf
- Hemerocallis taeanensis S.S.Kang & M.G.Chung
- Hemerocallis thunbergii Barr (syn. H. serotina Focke, H. vespertina Hara)
- Hemerocallis yezoensis H.Hara
- Hemerocallis nana W.W.Sm. & Forrest
Two hybrids are recognized:
- Hemerocallis ×exilis|Hemerocallis ×exilis Satake = H. fulva var. angustifolia × H. thunbergii
- Hemerocallis ×fallaxlittoralis|Hemerocallis ×fallaxlittoralis Konta & S.Matsumoto = H. littorea × H. thunbergii
A number of hybrid names appear in the horticultural literature but are not recognized as valid by the World Checklist of Selected Plant Families. These include:
- H. ×hybrida
- H. ×ochroleuca
- H. ×stoutiana
- H. ×traubara, H. ×traubiana
- H. ×washingtonia
- H. ×yeldara, H. ×yeldiana
See also 
- Arlow Stout - pioneer in the hybridization of daylilies
- Siloam daylilies - over 450 daylily cultivars registered by Pauline Henry.
- Sunset Western Garden Book, 1995:606–607
- "International Daylily Groups". American Hemerocallis Society.
- "Weeds of Wisconsin" U.S. Department of Agriculture. retrieved 10-26-09.
- "Dayliles Frequently Asked Questions". American Hemerocallis Society. American Hemerocallis Society, Inc. Retrieved 12 June 2012.
- Daylilies undated info page at University of Nebraska. Accessed August 1, 2007.
- RHS Plant Selector Hemerocallis 'Beloved Returns' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Green Flutter' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Red Precious' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Berlin Lemon' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Helle Berlinerin' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Royal Mountie' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Berlin Red' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Lemon Bells' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Stoke Poges' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Berlin Red Velvet' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis lilioasphodelus AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Tetrina's Daughter' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Burning Daylight' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Marion Vaughn' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Whichford' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Cartwheels' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Missenden' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Chief Sarcoxie' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Neyron Rose' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Corky' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Nova' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Golden Chimes' AGM / RHS Gardening
- RHS Plant Selector Hemerocallis 'Pink Damask' AGM / RHS Gardening
- World Checklist of Selected Plant Families, The Board of Trustees of the Royal Botanic Gardens, Kew, retrieved 2012-02-09, search for "Hemerocallis"
|Wikimedia Commons has media related to: Hemerocallis|
|Wikibooks has a book on the topic of: How to Grow Daylilies|
- The American Hemerocallis Society
- Australian Daylily Society
- Canadian Hemerocallis Society
- Ontario Daylily Society
- Hemerocallis species by the Drs. Lobeck has species, hybrids, and cultivars; links; terms and Latin meanings; images and history of hybrids
- DaylilyDB Daylily Database — Largest online collection of community submitted daylily photos, searchable by cultivar, hybridizer, color, and registration year, providing data and photos.