I have several varieties of Japanese Persimmon that are 5-10 years old. Many of them have cracks developing on the trunk; the outer layer of bark seems to split open from the ground upward. The trees continue to bear but the cracks eventually stress the tree. What causes this and what should I do?
The potential damage of the cracks will be dictated by how deep the cracks are. It is not uncommon for trees to "sluff" off the outer bark. The outer bark is composed of non-living cells and as the tree grows this bark cracks and is shed by the tree. If the cracks are deep and go all the way to the wood of the tree then you may have a problem. Such cracks are normally caused by freeze or cold damage. Painting the trunks of the trees with white paint tends to reduce the amount of this type of damage. So check to see how deep the cracks are; if they are just superficial don't worry about them. If they are deeper, then paint the lower trunks with a white latex paint. This should help with further cracking unless it gets really cold.