Originally Posted by edwmax

Humm ... The average low temp for your area this past month is 47 deg F and the minimum temp was 35 deg F (10/26). I'd say your nanas have shut down (stopped growing) for this winter. Thus the leaves have turned dark and wilted. The fact all the other trees have dropped their leaves too helps bear this out. The precipitation for October was less than 1 inch, so unless you are watering the plant, stop.

Next the label indicating a plant is 'cold hardy' is only indicating that a "Mature" plant's root will tolerate cold temps to that indicated and/or the USDA Zones given. Young tender plants are not cold hardy until they mature. The cold temps at which leaves will drop is different ...

Next ... 'Cold Hardy' Cavendish bananas are listed for USDA Zones 8 to 11 (may be 7 for some varieties). Your growing zone is 6 or 5 and outside the low temperature tolerance of the Cavendish banana. You need to protect the corm if want this plant to grow next spring.