If you are wondering how this one turned out, please see the top image.
I lightened the sky, greyed out the distant shrubberies and lightened the shadows a bit to be more airy. I also moved the top of the tree further from the edge and made the silhouette more random. I also added brilliant light green over the yellow of the ground in light.
I tried to think of the principles of landscape painting which are that the sky is always the lightest mass (unless it is a sunny beach), the ground is next in value and the trees and upright masses (such as mountains) are darker in value. Things get more bluish and greyer as they go back in space. Although I liked the bright colour in Version #1, I think it has a more realistic feel now, what do you think?