or day lily Any plant of the genus Hemerocallis, in the lily family, consisting of about 15 species of perennial herbaceous plants distributed from central Europe to eastern Asia. Members have long-stalked clusters of funnel-or bell-shaped flowers that range in colour from yellow to red and are each short-lived (hence "day" lily). Daylilies have fleshy roots and narrow, sword-shaped leaves that are grouped at the base of the plant. The fruit is a capsule. Some species are cultivated as ornamentals or for their edible flowers and buds