Ok so the grass with a moving “Sun” (Directional Light) it causes the grass to light up intensively, I made the grass a 2 sided materiel, that didnt help. I have no clue what is going on with it.
As you can see above, the sun is behind the camera, it lights up the grass wrong. Does anyone know why this is doing it?
Bump, since no one is helping
BUMP AGAIN FOR NO ONE RESPONDING. For [redacted] sake, is anyone going to help with this? Seems like anything i place onto the landscape, does not get affected by any shadows caused by anything, terrain takes shadows, but the foliage does not, i place an object and it did not cast any [redacted] shadow. I checked to make sure that it was check to have cast dynamic shadows, and even static shadows, messed with it’s settings as well. http://i.imgur.com/fLHaKyc.png BUMPED
i bump this also…
got the same problems 
I know this is old but I managed to fix my issue like this by changing the landscape to two sided, putting a cub under my landscape and rebuilding the lighting. Hope this helps.
