Try using some peat humus in the soil. I used a rototiller and mixed that in. Works great. Also, see this thread:
http://forums.gardenweb.com/forums/load/ohioval/msg082024138104.html?7

Ok thanks, what I'm really trying to focus on is whether musa requires average good drainage or sharp drainage? I can add lots of stuff with my Mantis tiller... chopped leaves, more mushroom soil, some sand, and compost from my composter bin.

Well, it seems they can grow just about anywhere, according to info. at this thread -

Here is a link that might be useful: here

Hello, Some of my basjoos have been in the ground for years. I have a few that I lift for insurance (along with some sikkemensis) before I replant in early spring , I dig a hole and dump a bag of composted sheep manure in. I plant directly on to of this. Robert

My personal experience has been average drainage is just fine. I have clay too, and I think I threw some amendments in there but I didn't knock myself out. My basjoo is next to the south wall of my house too - that's a great spot.

I suspect many of us are getting ansy to uncover our banana plants and see what's left, if anything.

It figures, of course, that the ONE YEAR I decide to give it a shot at leaving one planted, is the ONE WINTER that's gonna be colder and longer than the year before.

Oh well, April can't come fast enough for me. LOL

Good luck to one and all.

I have clay too. I prep my area by hoeing off all the weeds and digging a hole. It seems like in this zone, it's more important to cover them well in the winter than anything else!
One thing though, if it's a low spot in your yard where water puddles in the spring, don't plant it there.

Organic Matter!! Just load that hole up with tons of composted, organic matter, and your banana will thank you. I'm not sure about the pH, but I do know that my eating bananas did poorly in my very low pH soil of 5.1. My M. basjoo did fine, but it was in a different area of the yard.