Answer: Lots of things can cause premature yellowing on your Autumn Blaze maple. Overwatering is one concern, as is excessive heat which can stress your tree enough to cause premature color change. Over ferilization can do the same. When tree roots are stressed the problem usually shows up lower down on the tree and works its way up (as opposed to diseases which tend to affect all plant parts all at once) which is what leads me to believe you are dealing with root stress. Maple trees should be watered deeply once a week to encourage deep root growth. If the roots are shallow and you water your lawn daily, the soil can remain too saturated for healthy root growth. Soil contains a combination of moisture and oxygen. Too much moisture drives out the oxygen and essentially suffocates the roots. So, while you probably do not want to stop watering your lawn on a regular basis, you can do both your tree and your lawn a favor by watering for longer periods of time, but at less frequent intervals. Since it's the height of the summer season now, it will be difficult to wean your turfgrass off of daily watering so I'll suggest that next spring you adjust your watering schedule and maintain it all growing season long. In the meantime, your maple will probably continue to change leaf colors and the brown leaves should fall off. I think it will recover and I think it will perform as expected next spring and summer if you change your watering schedule. Best wishes with your landscape!
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