Oenothera tetragona (Evening Primrose)

Oenothera tetragona
(Evening Primrose) Bright yellow cup-shaped flowers in June and July. Foliage turns a reddish bronze in the fall while basal rosettes of leaves remain evergreen. Native to the eastern North America.  It colonizes via stolons and runners but isn't terribly aggressive. In the wild, it occurs naturally in woodland openings east of the Mississippi River in acidic, typically rocky, but rich soils. Full sun to part shade, average soil. Height: 12-18" Spread: 12-24". Zones 3-8.