A perennial herb with grasslike leaves growing from a bulb. Flower a six-pointed star borne at the end of the branches, to 2½ inches across, sky blue or blue violet. One to two flowers emerge from a common spathe (a sheathlike leaf); each flower blooms for only one day, in the morning, and then closes in the afternoon. Blooms April-May. Leaves 3 or 4, very narrow, long and folded (thus the name “pleatleaf”), clasping the stem. Root a bulb deeply underground, often in sticky clay.
Similar species: Nuttall’s pleatleaf (N. nuttallii), of the Ozark Plateau, occurs in similar habitats but apparently does not grow together with celestial lily. Its leaves are narrower than celestial lily’s, and its flowers are more purplish blue and open in afternoon and close at night.