Evening?

 Hooker's Evening Primrose, but in my experience, which is limited, it only blooms in the morning.  The photo below shows the lone blossom surrounded by taller vegetation.  I spotted it while driving along Chandler Road at around 15 mph.  I would never have seen it if it were not blooming.  During the past several years I've photographed this species along this stretch many times, always in the morning.  By noon or some afterwards, the blossoms close and are barely noticeable unless one knows exactly where to look.  The other location in my local travels where they've often been abundant is in and around the ditch that flows along the north side of the Safeway parking lot.  Same pattern - blooming in the morning.  I've barely done any Internet research on this question, but I plan to soon.  I'll start by looking for etymologies for the Family Onagraceae and the genus Oenothera.  Even my favorite field guide for this area says it blooms in the evening.  Nothing like a misbehaving plant to arouse my curiosity.