| Family | ONAGRACEAE |
| Genus species | Oenothera oklahomensis (Norton) Hitchc. sect. Megapterium |
| Bibliography | Monde Pl. Rev. Mens. Bot. 7: 148 (1898) |
| Native Range | s. Kansas to n. Texas |
| Primary Biome | Temperate |
| Habitat | stony grassland |
| Altitude | 200-500m |
| Description | glabrous, leaves green, often reddish, 7-11cm, elliptic to lanceolate-elliptic, carnose, margins sinuate, conspicuosly denticulate, acute, flowers solitary, petals 4-6cm |
| Size | 5-30cm |
| Color | yellow |
| Bloom | spring, early summer |
| Ca | |
| Type | perennial |
| Cultivation | sunny site with a deep, drained soil alpine house, rich, drained soil, sun |
| Propagation | seed in spring, barely covered, germ. 1-3 months, 18-21°C division in spring; cuttings in late summer |
| Synonyms | Megapterium oklahomense Norton, Rep. (Annual) Missouri Bot. Gard. 9: 153 (1898) Oenothera macrocarpa var. oklahomensis (Norton) Munz Oenothera macrocarpa ssp. oklahomensis (Norton) W.L.Wagner |
| Territory | 7 Northern America 74 North-Central U.S.A. (KAN Kansas, OKL Oklahoma) 77 South-Central U.S.A. (TEX Texas) |