Clear lighting data

Hello,

I am having problems clearing lighting data from the terrain trees.
have tried the generate lighting/clear baked data pull down with no success.
looking at the provided image, on the left you can see which objects where in a shadow.
project was originally made in unity 4

thank you

 

I have also found that if i replace a tree it has the correct lighting, but i dont want to have to replace all the trees.