I over-winter 'Black Magics' in large buckets of water in my cool garage. Works great and haven't lost one yet. The bucket is filled with masses of roots by Spring.

Thanks Dave. But did your black magics have a bulb or tuber? If I take Elaina out of her pot (a huge tub actually) and find only a mass of roots, are you saying to keep them in a tub of water like you did? I have an unheated garage, but sometimes when I get in my car the water in my water bottle is frozen...

They probably had very small bulbs, but were not really evident. I would dig them, wash off all the soil with a hose. You can probably trim back many of the roots a fair amount. It will generate new ones. I think they all have tubers...albeit very small ones. I have an Elena that I will overwinter the same way. Very similar to Black Magics.

Here's what the Black Magics looked like at the end of the winter after water bucket storage. I think with EEs with very small tubers, this is the best way to overwinter them. They really take off in the Spring when they have this many healthy roots.