Hey there, American Scandinavian here...might be of some help. Agree/disagree you can't grow collards, etc. there. Somewhat similar situation. Transplanted California who moved to a state where eating greens/produce year round (or at all) is alien. Plus I now live by choice (California = deadly fires, tourists, taxes), in a beautiful but very rural area and a one hour drive to actual produce, not canned collards (yuck?!) in a can. Yes, I actually saw that in the only store here, one of those lovely dollar stores.
Three years in, I have with the help of husband, a very large garden. Heading into fall with frost predicted in two weeks. In the winter (while much milder than yours), it can get to minus 17. But here's the thing. I harvest many different types of veges year round. This winter I will have: many kinds of lettuces, bok chois, green onions, leeks, beets for beets and above ground tops to steam, spinaches, kale, mustard, radishes, swiss chard, turnips and turnip tops, etc., etc...and, yes, collards in the snow.
How? You know those plastic tubs you buy stateside at the big box stores and pack away stuff in your garage/attic? I make small planting beds that exact size, then plop the tub (minus lid of course) over the small plant or seed area about to come up. Right now it's beautiful fall weather, but as soon as it gets frosty in the evenings, on they go and stay on for the entire winter. They come off or are lifted slightly with a small wooden wedge if I need to
water, to pick my produce, check out for growth or slug removal, or to let the heat out if it gets too toasty warm.
People thought I was crazy here. Until I gifted luscious spinaches and lettuce greens with beautiful red radishes and green and white bunching onions during a blizzard on Christmas day. 😎 They questioned why we didn't have a
greenhouse (on the list but I will still use tubs for a bigger planting area) or a high tunnel (would never withstand our high winds out here on the pasture.) If I were you, I would give it a try. If you don't have great soil, buy two bags of potting soil, cut out plastic in top leaving the plastic sides to hold in the dirt. Plant seed while it is warm
enough to come up. If too late already, put tub over potting mix and warm up soil for a week or so before planting. Then, if this latter, late method, water the seed with warmish water, not outside hose cold water. (Yes, I've had success with this method!)
Obviously, the tubs need to be the clear ones. I would double up the tubs in your area. (As in 2 stacked on top of each other.) We get 75 mph winter winds so you have to figure out a way to anchor the tubs down but still have it easy to get in and out of them. I've often scraped off 5-6 inches of snow to harvest and to let sunshine come through tub. I anchor mine down with either wooden or metal tent stakes pounded into the ground before it freezes, and then attach bungee cords so you can easily access your produce. Very snug. If you don't have access to the tubs, you can probably buy online. I actually got some from Amazon once because didn't want to drive the mountains in bad weather.
Yes, things grow incredibly slow in the cold and you may only get one cutting of collards. That's why you want a small to medium plant going before the weather gets really cold. However, you might be surprised. I harvest loads of tender lettuces by cutting off the leaves about 3 inches up so it can regrow throughout the winter. And, even though just the two of us, I have 76 tubs this year. Yes, I like fresh veges! Yes, I believe my health issue are helped substantially by eating Real Food. Alternatively, you could just use this tub method to speed up your short growing season in the spring/summer. Maybe a tub over growing collards, plus garden shade cloth on top so it doesn't get too intensely hot under the tub. Plus a little
wood wedge to let heat out if you are doing this in summertime?
Our growing season is very short up here in the mountains, too. But with my tub system, my growing season is year round. In fact, I have kale and mustard spinach (yes, a combo plant, yes, yummy) that I've replanted to another area that were planted last fall, survived minus 17 degree blizzards, and are strongly going into their second winter. Of course, you have to monitor when the tubs go on and off for spring/summer. And, I use shade and bug cloths as necessary.
Cold weather
gardening IS possible. Good luck!