Oak trees.

Oak trees start their leaves as a lime green colour, we call this coming into leaf. They are only open a few days before they rapidly change to a much darker green. The oak tree pumps things through the leaves that are relatively indigestible, meaning that the small larvae that were nibbling them haven't had the opportunity yet. So by doing this the oak leaves have a greater chance of surviving to then go on and photosynthesise, allowing the tree to take the energy from the carbon dioxide, sunlight and water.