How do I handle tree shadows?

Unity Engine
1

I’m making a forest that has one directional light. My problem is that every tree, instead of just the ones in front, have the lighting applied to them. What should I do about this? I’d appreciate it if you guys could tell me EXACTLY how to fix it, since I know nothing about how lighting works in Unity.

EDIT: What I mean is that all the trees are bright on one side, when only the trees in front should be. Pic:

2

Why is that a problem?

–Eric

3

Screenshots?

4

Sorry I didn’t give enough detail. The problem is that the trees are bright when they should be dark.

Pic:

The trees closest to the camera look fine, but the ones in back shouldn’t be bright at the trunks.