IMHO, if your intent is to try to overwinter inside anyway, you have little to lose, you'll be digging your plant up anyway. Hopefully, you've mulched the plant earlier in the year. As long as the frost has not penetrated the soil/mulch down far enough to cause the root mass to freeze, and the root still appears to be firm and healthy, dig it up and carry on with your plans. If the root appears frozen, well, it's an opportunity to head to the nursery for something new next spring! Hope the root is still cozy and protected under your mulch!
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