bigdog

Cavendish bananas seem to have more trouble than others when trying to maintain the pseudostem intact storing it bareroot. I would recommend potting it up into the smallest pot you can cram it into and still have some soil in it, and storing it in your basement. 70F will be fine. Water only about once per month, or even less. It's not likely to grow many roots at that temperature, so watering it more than that will just cause rot. You can store it dormant at those temps also, but the pseudostem may dessicate significantly. If I could make just one suggestion to you, get rid of the Dwarf Cavendish if you want fruit. It just isn't a good choice for any zone colder than 9b. Try a Dwarf Orinoco instead.

I have stored plants in a closet inside the house before, at room temperature, and they did OK. Yes, temps between 45F-60F are ideal for storing them, but you can get away with higher temps. Just keep them away from your furnace, in the coolest corner you have in your basement. Good luck!