Hi. My J-maple’s leaves are turning reddish and brownish and are drying up and curling at the edges. It is in a shady spot next to the house, and hasn’t gotten much rain. I have been watering it daily.
The Toronto Master Gardeners get many questions on problems with Japanese Maples – often brown and curling leaves. Below is a link to the response to a question asked earlier this August which I think you will find helpful:
You may also find the following fact sheets from Landscape Ontario of use: