Oenothera fruticosa (O. tetragona) looks like this. This is one of those genera that is not settled, however, with there not being a consensus unless something recent like the Flora of North America project has laid the matter to rest.
Sundrops, Oenothera fruticosa. http://xrl.us/nnt9 URL to pictures of mine. http://xrl.us/nnt9 Common Names: COMMON SUNDROPS · EVENING PRIMROSE · GOLDEN SUNDROPS · NARROWLEAF EVENING PRIMROSE · SUNDROP · SUNDROPS Detail is here. Description of Sundrops. http://xrl.us/nijt http://xrl.us/nijt Durgan.