Tree coliders in unity

I have painted trees from the terrain inspector onto my world, and I was trying to add colliders so my player does not walk through trees. I have tried using mesh colliders and capsule colliders and nothing works. I placed the prefab of a tree into my game and then added a collider and placed it back into the project window, then went on edit trees and selected the tree with the collider but it is still not working. the trees are LOD trees but im not sure if that has something to do with it. could someone help me please, I am new to unity and really struggling, I have looked at many tutorials

 

Are the trees in the background, or separate game objects?

 

I'm not sure what you mean, the trees are terrain trees, i painted them using the terrain inspector