Your backlighting doesn't work for this image, the green is hardly noticeable, it is too dark. Try lighting it from the front or side for better colour.
Nice idea, but you need some sort of light source shining up on the leaves, like fill flash or even a flashlight. The dynamic range, the difference between highlights (sky) and shadows (leaves), is too much for your sensor to capture and this doesn't work as a silhouette.
The backlighting of the sky did not maintain the green color of this leaf. Perhaps if you had put a reflecting board below it with your camera in between, it would have lit the comp up better.