I agree bubble wrap and insulation don't work without a heat source, I do believe it is possible to
obtain some heat from the ground. This was discussed in a previous posting by OlafHenry. [Citation needed]
Last year, I was able to save a 4' basjoo stalk through our Pennsylvania winter. It wasn't as cold as some years, but still there is usually a few days of arctic chill. Some days, the highest temperature was below 20F and we even had some nights in the single digits.
My original thread on this is here:
Uncovered my basjoos in Pennsylvania!
I think it is possible to save individual stalks with the insulation method, however its probably not practical for a large mat with multiple stalks. Like the ones Cincinnana is showing.
Based on my expereince, if the corm is large enough, basjoo plants can recover their previous year's height very quickly. So the extra effort to save the stalk will only be noticed in early spring....
erik