I've been growing aloes since the late eighties at my home in Apache Junction, Arizona. On January 14, 2007 we had a very severe freeze. It was below freezing for several hours. The coldest it got at our home was 21 degrees Fahrenheit. When we got up that morning and looked at the plants outside it was awful! Aloes were frozen solid like Popsicles. As they thawed out the yard had a strange smell. You could see where the plants were damaged, some had dark green wrinkled areas on the leaf tips and some plants turned all limp and wilted. My 15 gallon Aloe helenae froze solid. Over the months its stem died and I cut away the crown. As of November 2007 the crown appeared to be rooting in, but I can't be certain yet if it will survive. We lost SO MANY plants! I dumped probably hundreds that were in pots. I had more empty pots than plants. The ones in pots were hit hardest. Plants that were damaged would look like they were recovering, then they would die. I saved a large aloe dhufarensis, a large aloe fleurentinorum, two old aloe pachygaster and a small aloe speciosa by cutting away the crown. I set them in soil in pots after the cuts had healed and they eventually rooted in. I learned if I saw an aloe that was thin when others near were fat it's stem or roots had died. I have a medium aloe africana that way that I need to cut the crown off of. The most tragic loss was a large Aloe ramosissima that flowered three times. The hardiest aloe was the big aloe littoralis. It had very little damage. We were unprepared for such a hard freeze. No one knew or suspected it would happen. The plants that were left were the ones that were able to survive the hard freeze. We learned the hard way which plants were hardy and which were not.