Deebie, I agree, skip the plastic. I only grow two gingers, the 'White Butterfly' and the 'Shampoo'. The butterfly did well last winter but the shampoo was very late coming up and even then, had really stunted growth. The butterfly has bloomed well and the shampoo won't. I covered them both with a foot or so of oak leaves and nothing more.
The shampoo is in mostly shade, and I'm going to move it this fall so that it gets much more sun. At least that will help warm the soil better during the winter months.
