Nemastylis nuttallii

Nemastylis nuttallii, the Nuttall's pleatleaf, Ozark celestial-lily or pine woods lily, is a plant species native to Arkansas, Missouri and Oklahoma in the south-central United States. Some authors have mistakenly called this species "N. coelestina".
"Nemastylis nuttallii" is a bulb-forming perennial herb up to 40 cm (3 feet) tall. Stems are usually unbranched. Leaves are very narrow and linear. Flowers are pale blue, opening in the evening.