My Basjoo's are established but past winters ( except this past winter ) I just mulched and left them as is. Cleaned up the dead leaves. Stalks survived and I had instant bananas in Feburary. This past winter we hit single digit temps ( first time in 15 years) and it knocked all mine down to the ground. I thought I lossed them all but all sprung back ( from ground level ). In my first year I built a 4 FT fence around mine, filled with leaves and covered with plastic. You can try this method but its a lot of work and if not done right will rot if water gets in. My Basjoos have done pretty well with the occasional 20 degree nights and one or two nights in the teens. However no match for 9 degrees although the corms survived .

Another method to protect them is to collect bagged leaves, either your own or from your neighbors. You have to wait until the leaves start falling but usually you can get them in late fall before the extreme Winter temps comes in. Lay them around your stalk and you can stack the bags up and tie them together to keep them in place. Come Spring, haul them to the street for pick-up.Easy placement and clean-up. Basjoos are cold hardy so you have time to collect leaves before Winter sets in.

I'd really like to guarantee, as much as I can, that the stem survives this winter. I hadn't thought about the possibility of rot. Do you think I could dust it with a copper fungicide just prior to insulating with leaves? I was going to top everything with a huge black garbage bag to keep the water out, then cover with some reed screening so it doesn't look too ghastly.

Not sure about the fungicide. Main thing is to keep insulated and dry. Put enough insulation around on the ground to protect the corm. I have read on here some people stringing Christmas lights around palm trees and banana trees and turning them on only when needed.