Answer: Japanese maples generally do best in morning sun and afternoon shade. Shade cast from taller trees to shield the maples in the afternoon would be perfect. Trees can suffer all manner of superficial wounds and recover without problem. The scrape you describe should heal over all on its own without any intervention. In fact, university studies show that wound dressings actually slow and interfere with the natural callousing over and healing of wounds. Don't wrap the wound and don't apply wound dressing. Just leave the area alone and it should heal up by itself.
Best wishes with your new trees!
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