Every 10 years, the definition of "historic" daylilies changes; in 2010, the American Hemerocallis Society defines the historic daylily as a species or cultivar that was registered with the society before 1980.
Daylilies are natives of Asia. The first tawny daylilies, Hemerocallis fulva, arrived in America with the colonists. H. flava, the "lemon" lily, and a Japanese cultivar, H. fulva "Kwanzo," grew in the United States throughout the 19th century.
A.B. Stout, director of Laboratories at the New York Botanical Garden, conducted extensive experiments on daylilies and created hundreds of new cultivars from 1911 through the 1940s including Flore Pleno and Green Kwanzo in 1917, Europa in 1929, Dauntless in 1935 and a variegated Kwanzo in 1947.
Breeders and hobbyists created hundreds of cultivars in the 1930s and 1940s, providing plants for home gardeners. Pauline Henry, of Siloam Springs, Georgia, contributed hundreds of cultivars, beginning in the 1960s. Stella De Oro, Walter Jablonski’s ground-breaking 1975 re-bloomer, is now an historic daylily.
The AHS awards several prizes each year including the society’s top prize, the Stout Silver medal; Stout’s own Dauntless won the medal in 1954. The society also designates historic daylily gardens.