Too much water drowns roots by excluding oxygen. Too little kills by drying them out. Either extreme is a possible cause. Excessive fertlizer applications can burn roots. I suspect the problem is due to a soil moisture extreme. Try to keep the soil evenly moist. If the area drains poorly it may be necessary to dig the plant in November and then redo the bed, raising it up higher, then reset the plant.
Good luck with your Japanese maple. Thanks for the question. Please stop in again soon!
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