Hortiscope: Heat stress causes trees to drop foliage

Q: I planted five arborvitaes in large pots last fall. About a week ago, they all turned brown. However, there is a little green on the exterior layers. The summer heat has been brutal, but I have been watering regularly. Is this just a simple case of heat stroke? Is there anything I can do to save them?

By: Don Kinzler, INFORUM