Hemerocalis 'Corky', also known as day lily, is a plant of the lily family. The hemerocalis is a deciduous perennial that flowers from the end of May to September. Hemerocalis 'Corky' produces beautiful bright yellow flowers with brown streaks on the back of the petals. Well known for its hardiness, Hemerocalis is a hardy perennial and one of the longest-lived perennials. To make the flowering last: prune the flower stems after flowering.