Answer: If you've just recently planted your tree, I suspect the yellowing and curling leaves are simply a sign of transplant stress, coupled with reaction to the hot weather. Once the tree establishes its root system, it should perk up (although the yellowing, curling leaves will probably be shed). The best thing you can do for your new tree is to water it deeply once a week. I build a water basin or watering well for each of my new trees and shrubs. Fill the basin with water, allow to drain, then fill it a second time. This method of watering concentrates the moisture over the rootmass and allows it to trickle down, wetting the entire root mass.
Best wishes with your new tree.
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