I’m toying with the idea of setting up a trench greenhouse at some point, in order to be able to overwinter tropical or semi-tropical perennials (cough banana plants) more easily.
I love the way the Russians did it with citrus – link here:
And I’m thinking it would be a good first stage to get seeds that are used to my soil, which I can then plant in abundance with a little less cold protection each generation, until I’ve finally bred things that can handle my winters without protection. Bananas especially, but there are an awful lot of other not-cold-tolerant fruiting perennials I’m interested in, too.
What do you think would be a good way to set one up? Would it be enough to dig down only two or three feet in order to give some perennials that are only one zone away enough protection? That seems like a good proof-of-concept to see if I really want to do it on a larger scale later.
How would I keep the walls from collapsing? What kind of lid would I use? What would be simple and easy to make with stuff I could find or make easily?
If we can come up with something like that, it would be useful to lots of us who want to start the process of working on locally adapting perennials that are usually only able to live in a zone or two warmer than our own.
Any ideas?