There is always hope. Give it a hydrogen peroxide treatment and wait. Keep the roots fed and watered normally, don't fuss with it. As long as the roots don't die there is hope that a new crown will start off the base.

There is clearly a major difference between being below zero for a few hours in the middle of the night, and being below zero for days on end. This is one of the problems with going by the listed climate zones; the zone is defined principally by minimum temperature, but this does not take into account what the average temperature is. Winter-hardy agaves can survive in places like northern Arizona and Utah, where the record low temperatures are in the -20s F. It snows on plants, and gets really cold (at least for short periods of time). But you need to remember what the climate is like there, if you live in the east. Because the air is dry and it is usually sunny, high temperatures clear freezing on most days, and it is not that common for highs to stay below the 20s. Thus, plants are not usually frozen solid for very long. Additionally, conditions are generally dry, which helps a lot for these plants. Since I live 1-2 zones colder than most succulents get (zone 4, here, it was -22 F this morning), I can't expect many to make it through being frozen solid for several months, then dealing with mucky conditions during snowmelt. So, I'm experimenting with keeping some plants dry and cold in pots in my unheated garage, where it seems to stay between about 5 F to 30 F during the colder parts of winter. This year, I have an Agave parryi, Nanathus transvaalensis, Rabia albipuncta, Echinocactus texensis and a Delosperma on a windowsill in there. After a few weeks of being frozen, I brought them in and defrosted them. They were all OK except the Rabia, which turned to mush. The others went back out, and we'll see how they do in the spring.

Posted accidentally on wrong forum. Sorry This post was edited by gonebananas on Wed, Jan 15, 14 at 18:34

It was not exposed to subzero temperatures at all. What I think happened is that the water got trapped in the leaves, causing the leaves to rot at the base. The root system is vigorous and still looks very healthy, so I will try babying it to see if it can come back. At this point, there is zero top growth and just a nub of a stem left. Thanks for the reply, I will do all I can to aid in its recovery.