Interesting info Evening primrose opens at dusk and stays open through the night and much of the morning. Usually closes by afternoon.
Botanists have a hard time identifying Oenothera by species because it is highy variable.
I found this related plant in the wet woods, but I haven't been able to identify it yet. A few plants found in wet woods as early as June. More plants found in sunny field as late as August. Varieties found throughout Indiana. Also known from Labrador to Minnesota and from Florida to Texas.