Oenothera missouriensis
Large, showy, yellow poppy like 4" flowers bloom June to August. Grows 8-12" tall. Long dark green foliage to 12" wide. Effective groundcover in dry sites. Attractive seedheads. For contrast in texture pair it with Coreopsis.
Full sun in average, well-drained soil. Great for hot, dry areas. Drainage in winter is important.
Evening Primrose, Ozark Sundrop