This message was edited Friday, Aug 16th 12:56 PM
Oenothera caespitosa maybe? http://www.desert-tropicals.com/Plants/Onagraceae/Oenothera_caespitosa.html White Evening Primrose being one common name.
It is oenothera, but probably speciosa=Alba- Showy primrose the leaves are thinner and not as fuzzy as shown in caespitosa. I got my start from one of the people at the farmer's market who grows loads of flowers on the farm, but usually only the common name is known. It is open during the day and into the evening.