My Japanese maple’s skin is peeling off. Is this a disease?
Thank you for contacting the Toronto Master Gardeners with your question about your Japanese Maple. It’s difficult to be sure about what’s happening with your tree based on your picture but here are some suggestions.
It doesn’t look like your tree has any disease but it’s difficult to be sure without seeing the whole tree and having more information about its age and the growing conditions in your garden. Did you notice any symptoms or anything out of the ordinary during the growing season last year ? Did it leaf out normally and retain its leaves until the fall ? A common disease with Japanese Maples is Verticillium wilt. Usually the first signs of this disease are sudden yellowing and browning of leaves and wilting of the leaves and branches, usually on one side of the tree. This disease is caused by a fungus called Verticillium dahlia that lives in the soil and infects the roots, then spreads through the plants vascular system into the branches. It causes the plant cells to plug themselves so that water can no longer reach the leaves. This disease can also enter the tree through wounds (which your tree does appear to have) on the branches and trunk. There is no cure for it. You can check to see if the branches and trunk are still alive and well by scratching the bark with your fingernail, starting at the tips of the branches and working your way back and down the trunk. If there is green wood below the bark, the tree is viable in that area. If not the dead wood should be pruned out (pruning tools must be sterilized so as not to spread the disease as you prune). Here is more information on Verticillium wilt :
Another possibility is injury related to the weather. Japanese Maples are quite vulnerable to cold temperatures, to freeze / thaw cycles, and to winter sunscald especially if the tree is exposed to sun from the southwest. All of these conditions can cause bark to crack and peel. Often the tree will heal itself from these injuries, but the problem is secondary injury from birds looking for insects or insects that bore into the exposed trunk or animals like squirrels and rabbits that chew on the bark, all of which could lead to disease. There appear to be wounds that have begun to heal on your tree trunk (looks like some callus has formed around the edges of the wounds). Were these wounds there last year ? They may heal themselves, but you should inspect the tree regularly for insects and signs of disease in these wounds. There are products available at garden centres that can be used during the winter to protect young trees from animals that want to chew the bark.
Finally, it looks from your picture that your tree might be planted too deeply. This may or may not be related to what is happening with the trunk, but it could cause problems down the road. The roots of a tree that is planted too deeply don’t grow and develop properly which affects the health of the entire tree, and the bark at the base of the tree that should be exposed to the air can rot from disease. Trees should be planted so that the flare at the base of the tree where the roots start to spread out is flush with the soil line, so you should be able to see the top part of the flare. Also it looks like there is mulch right up against the trunk, which will also lead to disease and rot. You can push the dirt and mulch away from the trunk until you can see the flare. If this is below the surface of the soil, then you could consider replanting in the fall so that the tree is at the proper depth. Mulch should be kept about 6 inches away from the trunk.
You might want to have a certified arborist take a look at your tree to provide a second opinion. The Landscape Ontario website can provide a list of arborists in your area :
Japanese maples are such beautiful trees. Good luck with yours!