For over a century, daylilies that escaped from colonial gardens grew in fields and lined country roadsides. From a few original cultivars, scientists and hobbyists have made the daylily a star of the perennial garden. Today, hybrid daylilies are available in a variety of colors and flower types completely unlike their Asian forebears.
Daylilies are native to East Asia and were most likely brought to Europe in the 16th century along Renaissance trade routes. Of the dozen or so species grown in Europe's gardens, three types became important to the development of the modern daylily. Linnaeus classified two of these plants in his "Species Plantarum," published in 1753. They were Hemerocallis Lilio Asphodelus flavus "a" and Hemerocallis Lilio Asphodelus flavus "b." Today they are known as H. lilioasphodelus and H. fulva. H. lilioasphodelus is often called called H. flava, or "lemon lily." H. fulva is the common tawny or ditch lily. These two Chinese daylilies and a Japanese species, H. fulva "Kwanso," classified in Kaempfer's "Amoenitatum Exoticarum" in 1712, formed the basis for early experimentation in hybridization by A.B. Stout at the New York Botanical Gardens.
Today's daylilies are one of three genetic types. Diploid plants have two sets of chromosomes. Their flowers are smaller but come in a wider assortment of shapes. There are more pink and double-flowering daylilies. Tetraploids have four sets of chromosomes. They are generally larger flowered with sturdy scapes, the stems that hold flowers. They are larger plants in general with more intense colors; their larger collection of genes makes breeding for color easier. H. fulva "Kwanso" is the only known triploid daylily with three sets of chromosomes; it is a large, late-blooming double-flowered plant standing up to 4 feet tall. Once grown, hybrids are classified by size, color, color pattern, texture, branching habits and time of bloom during the season and day. Newer hybrids also include semi-evergreen and evergreen varieties that grow in frost-free growing areas.
In addition to descriptions of types of daylilies using size and color, varieties are classified according to flower type. The Tawny and lemon lily species have simple triangular flowers: six petals gently curving away from the center. Many Siloam hybrids are typical circular types, filling the entire area around the center. The trumpet type resembles a true lily, flaring outward from the center. Star flowers have long, pointed petals. Spiders have petals that are at least four times as long as they are wide. Unclassifiable or irregular petals are called informal types. In addition to overall shape of the flower, individual petals may be flat, opening straight out around the center, or recurved, curving back like a Turk's cap true lily. Three or the entire six-petal layer may be ruffled around the edges. Double blooms have a second set of six petals that may be or may not be similar to the first.