I would go back and photograph when the sky has dark clouds and ideally with strong direct sunlight hitting the trees(as noted above).
Stunning idea. I think, the best moment for this shot is when the last sun-beams hit the hillock, just before a thunderstorm is sending its lightning strikes to the oak trees (and the poor photographer is facing his cruel fate ). Now you know the reason for those odd-shaped trees!
But anyway, I'm carefully watching the weather-forecasts...