White Evening Primrose, Oenothera caespitosa, is also called Tufted Evening Primrose, and is a hardy perennial for desert landscapes in both the Tucson and Green Valley areas. In fact, this tough plant can handle temperatures well below zero. It is native to the west, and found in elevations from 4500 to 7500 feet.
While cold hardy is a plus, this plant can also handle our desert sun provided the drainage excellent. The White Evening Primrose hates poor soils and heavy clay, and will die out.
The flower show is what makes this plant special. The huge 4 inch diameter white to light pink flowers appear in the spring and summer, opening in the late afternoon and fading the next morning. The flowers are fragrant, adding another dimension to this petite plant reaching only about 1 foot tall and wide.
Reference: Mountain States Wholesale Nursery and Gregg Starr Nursery Plant Info Sheet, 1999.