A terrific low water use plant, capable of withstanding the beating sun and gravelly or sandy soils. Missoula is on the western fringe of this species' range, but they are well-suited to the drier conditions of the Valley bottom. The giant yellow flowers open in the evening and close in the morning (but it happens pretty slowly, you'll see the flowers, I promise). This plant forms a tight rosette of narrow toothed grey-green leaves and doesn't spread, so perhaps plant a couple for more visual impact. This is a good candidate for a sunny roadcut  or rock garden. 
 
Plant yellow evening primrose with low-growing drought tolerant companions like its paler cousin tufted evening primrose, cushion buckwheat, shaggy fleabane, alberta penstemon, and prairie junegrass .