I haven't read much about this, so I want to pass along my success and with overwintering spinach and having some available to eat for much of the late fall and late winter/spring. Growing up around here, I have never heard of doing it without a good cold frame. But, I was not a gardener then, and I know there was not as much in the way of tech materials to push the seasons.

In February of 2022, I noticed that some of my fall spinach survived the winter under a blanket of AG19. I knew I needed to try repeating that on a larger scale. So, last season I seeded a full 20' double row. It was after the potatoes came out, I think early/mid August. Germinating spinach is tough in that heat, and my huge bag of seed was getting old, but I put drip tape right over it and got some up. It took a lot of weeding too, but I cut a few good piles of spinach last autumn. After the last cutting, probably mid-Nov, I covered it with a sheet of AG19. When I picked it up in the end of January, there was more spinach ready to cut. There has been enough for a few salads a week since then. The only problem has been keeping it weeded, since the spring weeds like purple dead nettle love that protection as much as the spinach does.

Zone maps for here say 6b/7a, and the last two winters have been fairly mild. No ice fishing around here this year. About one week or so last year, in some coves. I think that direct seeding the spinach is also part of the key to staying alive over the winter. A transplant will not have roots as deep, and will have a rootball made of potting soil. I feel that the lighter mix would probably freeze harder. I have not tried fall transplants - they may work as well, that is just my thoughts on it.

I have 4 week old starts in the basement - while I may plant them out soon, the leaves are only about the size of a quarter. Probably May will be the earliest leaves picked from them. That is nearly 100 days after I started picking this overwintered stuff. So, I encourage everyone to try this, if you are close in climate. I am at 40.4N and last frost date is something like May 8 around here. It has been nice having fresh spinach for the past two months. (Yes we just ate some tonight, boiled 3 minutes in salt water with a white sauce with finely chopped venison pastrami mixed in.)

Very nice! I bet this would work for arugula too, but you might want to start it later.
I bet you could do Purple Sprouting Broccoli in SE PA.
Commonly grown in the UK, plants are started in the fall and they produce purple broccoli spears in spring. Way earlier than anything you could start in spring, afaik. They are extra hardy too. I have some in my greenhouse this year.

Purple sprouting broccoli, okay that sounds good. I was wondering what else would overwinter for early picking around here. Fall planted green onions is something I've never tried either, though I'm concerned about the those allium leaf miner for that. I've read that bug is spring and fall and affects the fall planting worse that the spring? But it would be nice to have green onions now. What we call "oniongrass" is really popping up now and if it were in a tended bed I could see picking it this past month.

I know I could do more with a cold frame, but this was as easy as throwing a sheet over the last cutting in fall, and walking away. The only problem is the spring weeds love it too - the adjacent, uncovered rows were practically weed free until this week while the covered row had weeds in late January.

The spinach row, Sept to yesterday

I overwintered some spinach by accident and meant to do it again, but have not been organized enough in the fall to do bed prep and planting. That year, I planted a fall lettuce bed one year, covered it with plastic row cover and we ate lettuce into early snowfall. I had planted spinach at one end, but the plants were too tiny to harvest that fall. Heavy snow and cold came and I never took the plastic off. It was sagging and covered with snow. The next spring, the small spinach started to grow again (lettuce was dead) and we had tremendous spinach early. We always have very cold sub-zero temperatures every winter, so spinach can take a lot of cold.

Even in the frozen north, that's cool. It has been mild here for 2 years with little snow. I wasn't even sure if how well this would work up in the northern tier of PA - that is 5A in parts.

I'd say a couple layers of agribon may be better than plastic, but maybe not. For sure, I started this row when the potatoes came out in mid August, and it was tough to get the 5 yo seed started in that heat. I seeded heavily and did every trick I could think of, including drip tape right over it. But it did the job and sunk those roots deep.

This year I may well lay down black mulch for the spring weeds. I can cut one with two lanes that match the double row, and just lay that over for winter, after the last cutting. Then the spinach rows would be the only place for weeds to come up, instead of the whole row width.