A daylily is a flowering plant in the genus Hemerocallis. Gardening enthusiasts and professional horticulturalists have long bred daylily species for their attractive flowers. Thousands of cultivars have been registered by local and international Hemerocallis societies. Hemerocallis is now placed in family Asphodelaceae, subfamily Hemerocallidoideae, but used to be part of Liliaceae (which includes true lilies). (source)