too late for this method now but next year you could cut back and leave in the ground..add some protection (mulch, straw, leaves etc) my neighbor has been doing this for years..someone here can suggest other methods..I cut then covered mine with a garbage bag full of leaves last year..pic#1 my neighbor's 10 or so years old bananas..pic#2 my 1 year old banana and 2 new this year..

I trim most of the outer leaves, shake most of the dirt off the root ball and stick in a trash bag. Place under the house in a non-heated space that doesn't freeze. Been doing it this way for 50 years. I've got bunches of bananas on 2 of my plants this year in Arkansas.

Had always cut mine down and covered them up. Last year I just left them alone! Not a one of them died! Had to trim leaves off of some of them and they are probably 25 ft tall now so going to cut them back. The ones with bananas on them are huge too and have had several (4 or 5 bunches of bananas) on them this year! Got a pod and 10 hands of bananas on it now! Lots of pups too! Think I will cut them all back this time! I thought with all the water inside they would freeze and it would kill them, but no! The came out early this spring with pods and bananas!

Forgot to tell you that my trunks are probably 12 to 15 inches around on the older ones!