Aranon

I live in Nebraska and last night our temperature hit the mid to high 20's so all the leaf growth on the basjoos have died and turned brownish, the pstem looks fine though. For our 5 day forecast it looks like our highs will be mid 50's to low 30's at night, should I cut back the stem now? This will be the first time I try to overwinter bananas. I have lots of grass clippings from mowing all summer and quite a bit of leaves as well, should I cut the stem back a few inches to the ground and pile the leaves/grass on them? I see lots of methods on overwintering them, some seem more complicated then others.

I planted them by cutting holes in between rubber matting (the kind used to stop weeds) The matting is fairly thick, would I need to place the matting over the grass/leaves? or in between? I have included some pictures showing the plants and the mats they are growing in.