Answer: If this is a brand new tree, I would strongly suggest you contact your retailer for advice, especially if there is a warranty.
A newly planted tree can go into shock for a variety of reasons such as being transported in an open vehicle, planting deeper than it grew originally, overwatering so the soil is saturated/sopping wet, being allowed to dry out at the roots, accidental herbicide exposure, overfertilizing, and abrupt change from shady location to a sunny one.
Make sure the tree is planted no deeper and no higher than it grew originally. Mulch with several inches of organic mulch over the root area, do not allow it to touch the trunk of the tree.
Do not fertilize, this would just add more stress.
Water as needed to keep the soil slightly moist like a wrung out sponge, not saturated and not dry. Use your finger to dig into the soil and see if you need to water. If it is still damp, do not water yet. When you do water, apply it slowly and thoroughly at the roots. After watering, wait a few hours and then dig down to see how far the water went; sometimes it can be surprising.
I hope this helps you trouble shoot. The best thing you can do to try to help it recover is water correctly.
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