My midtown Toronto mature Japanese maple has shrivelled crisp leaves. All of the leaves! Everything else in my flower garden is fine, so it seems the watering system must be working. I was away for 3 weeks and came home to this problem. What is it and what to do? Thank you.
Thank you for contacting Toronto Master Gardeners. There are two possible causes for the shriveled leaves. The first is leaf scorch. Although your sense is that your watering system is adequate, this has been a dry summer. From your picture, it’s not clear where the tree is situated but if it is near pavement, the reflected light can cause the leaves to scorch and shrivel. Since this environmental factor can’t be controlled, it’s best to avoid planting susceptible trees, such as Japanese maple or flowering dogwoods near pavement.
The other possibility is verticillium wilt. This fungus lies dormant in soil and enters wounds in the roots. The fungus restricts the flow of water to the branches and leaves. The branches blacken and leaves become shriveled. There is no cure for the disease. Trees can survive for a few years with minor symptoms but will eventually die. Unfortunately since your tree is covered shriveled leaves, this means that the disease is quite advanced. If this is the case, the tree will have to be taken down and disposed of in the garbage. If you decide to replace the tree, it would be important to select a species of tree that is resistant to verticillium wilt. You would also want to plant the new tree slightly away from where the Japanese maple was situated.
To help you decide how to best deal your Japanese maple you might consider consulting with an arborist. Landscape Ontario can provide a list of qualified arborists