Is there a way to make colliders fall asleep?

I have a normal terrain with lots of trees on it. They don’t tax my graphics, as long as I keep them billboard long enough, etc. But I also need them to have collision. So I created a pine tree prefab with a capsule collider and painted them onto my terrain. My framerate is normally between 40-80, but then it drops ramdomly to 3-5 fps. I know the tree colliders are the problem. (the verts and draw calls are fine)

So the question is, How can I fix this? By putting them to sleep? I don’t really know how that is done. Anyone have an idea?

Rigidbodies can sleep, which they do automatically (when they basically stop moving, depending on the settings you have in the physics manager). Colliders can’t sleep, nor would it be possible for that to happen, since they are never “awake” either.