I have dissected a scots pine that had ivy all over the ground . The tree was the healthiest scots pine I have seen. So some trees may be companion plants and some not. Again, other than blocking sunlight from needles and leaves I know of no published research showing that ivy kills trees. I personally do not like ivy growing on trees. The reason is because it covers up defects and signs of a high risk of hazard situation such as cracks and so on.
Does anyone have data (peer reviewed published papers) showing that ivy kills trees. I would like to read it and place it in my dictionary for all to read under hard to get docs.
Sincerely, John A. Keslick, Jr. Arborist