sego lily (sēˈgō) [key], ornamental plant ( Calochortus nuttallii ) of the family Liliaceae (lily family), also known in parts of the West as mariposa lily. It is native to the region W of the Rocky Mts., especially Utah, of which it is the state emblem. It has narrow leaves, beautiful tuliplike white flowers marked with purple, lilac, or yellow, and bulbous roots that were used by the early settlers for food. It is used in Mormon symbolism. It is classified in the division Magnoliophyta, class Liliopsida, order Liliales, family Liliaceae.