Variegated tapioca in zone 8a

I bought several variegated tapioca plants (manihot esculenta) last june. They grew rapidly from 1 to 6 feet in 4 months. By October, they were in decline, after having been repeatedly blown over by gusty autumnal winds. I was afraid to leave the tubers in ground over winter (they're only cold hardy to 30 f), so I lifted them and planted them indoors. I know the nonvariegated cultivar is cold hardy in zone 8a, but it I don't find it visually appealing. Has anyone in zone 8a tried mulching the variegated cultivar and have it survive our winter?

I'm not sure what the ("...they're only cold hardy to 30 f) refers to. If you're referring to the tubers, you should be perfectly safe. Ground temps in my gardens only went below 55f one time in the past 20 years. I know Sumter is a little colder, but I'd be surprised if there was more than 1 degree difference. If you're referring to the foliage, they'll die back every year after the first frost, but the tuber will be fine.