How could you build a snoasis?
backstory: I want to grow a tree that isn't suitable for the winters here. I had a nice tropical tree which I grew from seed in a pot, but it got so big indoors and clearly wanted to go outside that I planted it outside as a reward for being awesome. However, when winter came, I decided to protect it by giving it a blanket and some insulation around its core at the bottom of the trunk. Unfortunately this only caused mold to collect around the base and killed the tree. So... ever since I have idly wondered if there's a way to fashion some sort of insulating box at the ground level, kind of like the groasis that would let it survive a freeze in the winter.