Answer: The roots of your plant are hardy to about 20F but the top is tender so expect it to die back. I would either dig and pot it up for overwintering in a semi protected spot such as a garage, or mulch the base with a couple of feet of leaves enclosed in a wire ring, or a foot of compost piled at the base. This way when the top dies back at the first freeze the base will survive to resprout the following spring.
Best wishes with your banana tree!
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