I'm with Elaine, do lots of mulch. I look at it this way, you babied the plant all year so why do the bare minimum that MIGHT be necessary to protect it. You want your plant to form a pad and lots of pups. Then you can experiment away.
I've had 4 years with multiple nights below -10F (z5b years) since planting basjoo.
@Bubbles posted a link to a Logee's video in which they mulch a clump of Musa sikkimensis. Logee's is in z6a I believe and I've followed that procedure every year since.
What Logee's did is cut the p-stem to ~12"; add ~24-30" of straw mulch; add plastic sheet; add 12-24" more mulch. You want to mulch 18-24" out from the p-stem.
I transplanted a few last year. One pair of transplants I mulched to about 30-36" and plastic on top but no additional mulch and both survived, see photo. Another I mulched with a few feet of grass clippings and no plastic but it didn't return. I'll try this again this year with plastic on top.
I believe the Logee's video is no longer available but they have a page with directions here:
http://www.logees.com/howtoput...
This is very interesting! P-stems are cut much higher even though it states 12"!
A video on uncovering in the Spring.
https://www.youtube.com/v/Qcc_...
