Why are the flower petals turning brown or falling off recently planted bushes in clay soil of North Carolina?
Gardenia Bushes should be planted in moist and well draining soil.
Clay soil would not be recommend for success with this finicky plant.
Petal dropping and browning leaves can be due to transplant shock.
The plants new roots may be having trouble with the clay soil and it's lack of drainage.
Here are some links to refresh you on the growing and care information.