When we lived in Ohio zone 4-5 winters were bad. freezing ground,wet conditions,below zero temps every winter. I never did anything for my Basjoo mat,just cut them to the ground and always came right back.
fishoifc - lives North of me 4hrs away down the coast. We both have sand for soil that's it,very dry and hot/humid.We don't just plant them in straight sand
My Basjoo mats here don't seem to like the heat we have here on the coast. No matter how much I water. My other types all do great. They do like to be shaded more down here I noticed as the ones I gave my parents and neighbor's here,has them shaded and they are large.