How to extend growing season in Southern Minnesota?

Don't know if this will help but even if you get 1 new idea from it that makes it a winner:

https://www.motherearthnews.com/organic-gardening/growing-season-zmaz94jjzraw

https://www.gardeners.com/how-to/season-extending-techniques/5063.html

https://www.motherearthnews.com/organic-gardening/garden-know-how-extend-growing-season-zmaz07fmzsel

You're not alone! Here's tips from the extension agency: https://extension.umn.edu/planting-and-growing-guides/extending-growing-season

Nice site. I like the interactive map.

One thing you did not mention is putting tomato cages around any and all plants and wrapping them with plastic to help them extend the season. Farmer friends of mine in Iowa did this to all their plants in the vegetable garden and it really boosted their growth! Here is where it was applied it to some new planted trees: https://www.hometalk.com/diy/grow/plants/cages-for-more-than-tomatoes-37288024

Cages for More Than Tomatoes

I did that one year in the spring, it worked great 'cause I was able to plant some stuff I started indoors too early. I used 10 foot ½" conduit and made a 3/4 inch plywood form to bend it, then covered with 4 ply plastic.