Missouri evening primrose has lemon yellow flowers that open in late afternoon and close the following morning.
Oenothera missouriensis is a long-lived, drought-tolerant perennial that makes a nice ground cover around taller perennials and shrubs. Or try it in a large rock garden where it has room to spread. Hardy in zones 4-10. Also known as Ozark sundrops and Oenothera macrocarpa.
height 9", width 18"