Bark Has Split on Chinese Elm

Answer 1

If the bark has split clear down to the interior wood, then it needs to be sealed to keep insects out and prevent disease. There is a tar like product called Tree Wound Sealer on the market. Most garden centers have it. I believe ACE hardware carries it as well. Apply such a product to the split working it well into the split. Once done sprinkle it lightly with a fine sand to help make it less sticky, thus it will stay in place better if anything brushes against the treated area.