Actually, the ground here usually freezes very deeply. In my 51 years of life, this is only the third time that I can remember that that for the most part, the ground stayed thawed through the winter. And this season the ground did freeze a few inches, but the frost came out when the thick blanket of snow fell. And your definitely right, Polly, that unfrozen wet soil through is not good for lilies, especially Asian species.
Re: overwintering pots
I made some wood box frames that I wrapped in hardware cloth to keep the varmints out. When the ground freezes permanently, I will fill the boxes with the potted materials, everything from cactus to lilies to alpines and miscellaneous. Cover loosely with a tarp to keep the rain/ snow off until early to mid December, and then put them to bed with a light blanket and waterproof plastic over that.
This is a pic, although quite old, I used to do a lot more insulating, which I found to be mostly unnecessary now. Plants, even in pots, are much more cold hardy than you'd think, if the soil is dryish.
