Oenothera macrocarpa

Oenothera macrocarpa (syn. Oenothera missouriensis), the bigfruit evening primrose, Ozark sundrops, Missouri evening primrose, or Missouri primrose, is a species of flowering plant in the evening primrose family Onagraceae, native to northeast Mexico and the south-central United States, where it is found in calcareous prairies and limestone outcrops.