According to Flora of North America, Oenothera villosa ssp. strigosa is the locally common erect evening-primrose with relatively small (compared to Hooker’s evening-primrose) yellow flowers.  It is the native member of a complex of difficult-to-distinguish species, encompassed in an inclusive O. biennis in Flora of the Pacific Northwest (2nd ed.)  Following the more recent treatment in Flora of North America, our native plants with relatively open inflorescences (i.e., mature capsules not densely overlapping) are O. villosa ssp. strigosa.  Similar plants with denser inflorescences (i.e., mature capsules densely overlapping), which are also common in our area, are provisionally identified as either O. villosa ssp. villosa or O. biennis, as introductions from the eastern United States and Europe respectively.