It will likely depend upon the circumstances surrounding how the tree fell if it will be covered by the homeowner's policy or if you should make a claim through your own auto insurance carrier.

If the tree fell on your vehicle due to neglect by the homeowner, such as it was a diseased or dead tree that the owner knew should be cut down but did nothing, then it would normally be covered by their homeowner's policy. If it fell on your vehicle due to a storm or another "act of God" then normally their homeowner's would not cover it and you would need to place a claim through your own comprehensive insurance coverages.

If the tree did not fall on your vehicle but you ran into a tree in the middle of the roadway then again it would depend upon how the tree got there, as well as state laws regarding this type of situation. If the tree was cut down by the owner and they failed to get it out of the road then their homeowner's may accept a claim for your damages. If it fell in the roadway due to a storm or issues out of control of the home owner then likely their insurance would deny a claim.

If you ran into the tree in the roadway then this would go under your own collision cover if you had to make a claim with your own car insurance provider since you would have collided with the tree. To find out which insurer you should place the claim for your damage speak with both the agent of the homeowner's policy as well as your own auto insurance provider.