Good morning! I live in Oklahoma zone 7A. I'm curious how the folks in Oklahoma heat their greenhouse(s) in the winter? I've got tropical plants I need to house in my greenhouse once it's built. I have an avocado tree, and 9 pineapple plants. Of course I'll plant vegetables and fruits in the greenhouse, but my concern is how to keep the greenhouse warm for tropical plants.
I've enlisted a neighbor's son who owns an excavator, because the floor of the greenhouse will be 4 feet below the surface. My greenhouse will be built over the hole, steps put in. So I'm hoping the earth helps keep the greenhouse warm.