Thanks, JRP. This image was taken in a horticultural conservatory here in Milwaukee called the Domes about 3 pm (I think) in the afternoon. The sun was diffused through the dome that enclosed all the flora and fauna that is on display in one of the domes. There is a display dome (this one with spring flowers), a desert dome and a tropical dome.
The angle of the light where these lilies were planted was such that when I got down very low to the ground and pointed the lens up toward the lilies the sun was behind them and shining through them. The sun flowed between the lilies and the wall behind those plantings thus giving me the contrasting dark background.
This is one of reasons why it is so important to get low to the ground and discover how the light plays out. I thought it was pretty cool use of the existing light--pretty exciting results.