My favorite gardener constructed this nifty little low tunnel to extend the growing season. We should be able to harvest spinach almost all winter.
I’m not sure how this stacks up environmentally, since what you’re looking at there is a lot of plastic. Sure, it’s heavy duty plastic that should last multiple growing seasons, but still.
It may be better than buying plastic bagged spinach shipped in from California, but the greenest option would be to just eat local spinach during the regular not-extended-with-tunnels growing season. That said, it will be fun to get something out of the garden when fresh, local produce is scarce.