My favorite time to photograph flowers is late evening. I try to get to my site as the sun touches the horizon. I shoot until the sun is gone and the cool blues of twilight have taken over.
For those of you who do macro/flora photography, this might come as a surprise. Macro photographers often like the diffused lighting of a cloudy afternoon. After all, diffused light results in more saturated colors.
Check out this black-eyed Susan image, taken around 11:00 AM on a cloudy autumn day:
Notice how the yellows and reds pop off the screen.
But there is a certain magic that is produced by evening light. A magic that cloudy light just doesn't offer.
I'll leave you with an image that I captured a few nights back. It's an aster, taken at sunset.