Answer: Sounds as though your new topiary is suffering from transplant shock coupled with the summer heat. There's not much you can do to help it along other than watering deeply once each week. It is likely to look droopy until the roots establish themselves. If you can provide some temporary shade from hot afternoon sunshine, that might reduce the stress.
Just for future reference, it's always best to plant or transplant trees and shrubs during the cooler months of spring and fall - even if you purchase them in the dog days of summer. Cooler temperatures reduce the stress of transplanting and allow the roots to become well established before hot weather arrives.
Best wishes with your new plant!
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