Oenothera fruticosa is a day-blooming member of the Evening Primrose family. It produces basal rosettes, and single 15 to 30" rigid stems that are lightly pubescent, tinged with red, and bearing lance-shaped alternate leaves. The flowering stems are terminally branched and produce an abundance of bright yellow poppy-shaped flowers that are up to 2" in diameter. Individual flowers are short-lived, but the blooming period is long, extending for 2 months or more between late-spring and mid-summer. As fall progresses, new basal rosettes will form that will persist through winter, and acquire purple and bronze hues as the cold weather sets in.

Narrowleaf evening primrose is a care-free species and a good choice for tough spaces. It is shallow-rooted and will spread via stolons that are just below the ground's surface. It is however non-aggressive and its spread can easily be controlled by plucking out unwanted plants. Its preference is full sun, but it does remarkably well as a filler plant shaded by taller growing perennials, where the evergreen rosettes will also serve as a green mulch. It is not particular about soil, and will thrive in rich, moist, well-drained ones, just as readily as in poor, dry ones. [source: izelplants.com]