1. Cut off all the excess foliage which can't survive the winter anyways
2. Shrink wrap all the trunks
3. Add additional insulation if necessary
4. Stick a cut open plastic barrel over the entire banana stem
5. Fill the barrel with leaves
6. Add additional leaf bags with leaves if the stem is too long
7. Shrink wrap the entire set up to keep it stable
Here's the musa mekong giant which was much easier to over-winter since it is still very small.
The musa basjoos are a lot bigger so they require a little bit more work, but it will be well worth it if I am able to save most of the pseudo-stem to the banana plant can pick up growing where it left off this year instead of dying back to the ground.
I use leaf bags on many of my other plants such as elephant ears to hopefully get them through the winter and come back next spring.
Here's a semi-tropical plant that grows like a banana that lacks a pseudo-stem.
I am also saving all my bhut joloka hot pepper plants by sticking many of them in the same pot, and I will eventually place them by a window indoors. If I can over-winter these plants this way, I should be able to get a much faster start and faster harvest with next year's peppers. They were 3ft tall before I cut them back, and that would take up too much window space.
This one was in its pot the whole time, and not huge like the rest so I didn't cut it back.