I planted a southern magnolia tree in early spring and after a bad heat spell most of the limbs and leaves have turned brown. I put a shade over it to protect it from the sun. How else can I help it make it through the summer? This tree is particularly significant to me because I planted it with the ashes of my dead mother in an attempt to allow her to live on in the form of a beautiful flowering tree.
Watering is very important for new tree plantings, especially during hot dry spells.
Increase watering and mulching with 2 to 3 inches of hardwood mulch will help with moisture retention.
Shading it during the hottest part of the day may help.
Check to see if the limbs snap off or are still pliable. If the branches still bend they may still be alive and viable.
The leaves drying and falling off is the tree trying to protect itself with the stress.
I'm listing some links for you to refresh you on the care.
Time will tell and best of luck.