Tree colliders

How can I make my tree have colliders?
The main problem is that my trees aren’t a normal tree with billboard leaves.

EDIT: I found out that my problem lies in the treeprototypes, because when adding it through them them at runtime there isn’t a collider, but when manually adding it to the terrain using the brushes there is colliders.

It is this kindoff tree:
alt text

In the prefab for your tree, put some kind of collider on it. Then in the terrain, check the box that enables tree colliders.