How could you have an unheated greenhouse in Wisconsin?
I start using it in April when I move seedlings out there that I’ve started indoors. On a sunny day, it’s easily 70-80 degrees in there, the way it is sited.
Then, I grow things out until they’re ready to go into the ground at the end of May.
I also grow salad greens in there in early spring and late fall. This season I harvested the last of my greens around Thanksgiving. Then I give it up for the year, mainly because it’s a PITA to shovel a walkway to there from the house and Winter is my BREAK TIME from the garden. ;) In the middle of summer, it’s 100+ degrees in there and unless I’m growing cactus, nothing much can survive that blast of heat.
Right now it is 34 degrees outside and sunny. It is currently (10am) 64 degrees in the greenhouse.
Check out any of Elliot Coleman’s books. He grows in large, moveable greenhouses in Maine - all winter!
Also Niki Jabbour writes some great books on gardening year-round in unheated greenhouses and cold frames.
My unheated greenhouse gives me a head start in the spring and lengthens my ability to still grow some things into the fall. And it’s my She Shed, LOL!
https://www.eliotbarbara.com/read-our-books/
Niki Jabbour: https://www.amazon.com/Year-Round-Vegetable-Gardener-Matter-Where/dp/1603425683