Hi, 

This is typical on lave leaf plants at the end of the summer, especially with the high heat and drought conditions we had this past season. 

Did you supplement irrigation this summer? If not, it would be a good idea to water periodically this fall to help it into winter. We are supposed to get some rain this week, but it has been a pretty dry month so far. You could give it a good soak today by laying a garden hose on a slow trickle at the base for about 20 minutes. 

You can review out Watering Trees and Shrubs page for further guidance. 

The leaves will fall off this autumn and should be fine next spring. 

Emily

They are on the higher water requirement end but also just the LACE (sorry for the previous typo) leaf is delicate in full sun and the dark leaves soak up more heat. Are you feeling the soil after the lawn irrigation to see if its wet around the maple? It needs to be moist about 6 inches down to sufficiently reach the root area. If the irrigation is only running in the lawn for about 15 min. twice a week then it would not be enough. Are they spray heads? Is it reaching the tree? Are you doing it by hand or with a sprinkler? If you use a watering can or bucket, how much are you giving it?

Yes that probably wasn't enough time then. Just feel the soil under the mulch about 6 inches down. You can use a screw driver or garden stake to be able to get through hard soils.

That should be sufficient. You can check the soil after that time and see if it has soaked down enough then. The link for the Watering Trees and Shrubs page should can help explain more. Established trees need about 1 inch of water a week to not be drought stressed.