Answer: Some varieties of Japanese maple are not very tolerant of hot afternoon sunshine. They usually show their distress by developing crispy leaf edges. Some trees outgrow this sensitivity and others do not. If yours is a red-leaf Japanese maple with lacey or dissected leaves, it should probably be planted where it will get some protection from afternoon sunshine.
Japanese maples are also sensitive to salt so if you fertilized your tree when you planted it, or if it is planted in a lawn that you recently fertilized, this, too can account for the crispy leaves.
Finally, soil that remains too wet for too long can suffocate the roots which can show up on the foliage. My suggestion is to water your tree deeply but infrequently. Daily watering will keep the roots close to the surface and keep the soil, especially clay soil, too wet. Dig a well or watering basin beneath the tree. Flood the basin, allow it to drain, then flood it a second time. This will concentrate the moisture over the root system and allow it to trickle down and wet the entire root mass. Water once a week (twice if the weather is really hot).
Best wishes with your Japanese maple!
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