Daylilies (Hemerocallis) are part of the Hemerocallidaceae family, along with phormium. Though "lily" is part of the common name, the plants are not true lilies. They are members of the Liliaceae family. Daylilies are distinguished by the fact that individual blossoms last only a single day.
Native to Japan, China and Korea, daylilies were mentioned in the writings of Confucius (551-479 BC). For centuries, the Chinese grew the plants for their beauty and medicinal value. Their status as ornamentals was confirmed when Chinese author Chen Hao-tzu described them in a 1688 gardening treatise.
Daylilies probably traveled from Asia to Europe in traders’ caravans traversing overland routes or in ships that docked in cities such as Venice. The name "hemerocallis" was bestowed on the genus by Linnaeus in 1753.
Hemerocallis fulva, the common tawny daylily, and Hemerocallis flava, the "lemon" lily, came to America with 17th century colonists. The tawny variety quickly escaped the garden and spread widely. Beginning in the early 20th century with the work of A.B. Stout, daylily hybridizing took off. There are now thousands of hemerocallis varieties registered with the American Hemerocallis Society.