My corn plant was left outside an froze. All the leaves died but the plant itself, I think, is still alive. What should I do?
There are many different kinds of “freezing.” There is 30 degree freezing and there is below 0 degrees freezing. There is exposure for a couple of hours and there is exposure for several days or more. The lower the temp and the more prolonged the exposure, the greater the damage will be.
Cold damage affects the foliage first and foremost because the leaves are exposed and unprotected. The roots are somewhat insulated by the pot and soil so roots suffer less damage. That is a good thing because a Corn Plant can suffer extensive foliage damage, but it will recover as long as the roots were not badly damaged by the cold. Only time will tell if the roots are still viable.
In the interim, there is not much you can do. Of course, keep it warm. Trim off all leaves that are completely or mostly damaged by the cold. They will never recover. If the stems coming out of the top of the cane are shriveled, then they are unlikely to recover. Provide lots of very bright, but mostly indirect sunlight, no more than 6 feet from the nearest window. Reduce the watering so that the top third of the soil dries out before you add any water. Do not fertilize, repot or do anything else to try to short-cut what will be a long, slow recovery.
Look for signs of healthy new growth in the next 4-6 weeks. If you see none by then, you can assume the roots have been severely damaged and the plant will not recover.