"Winter Kill Temps For Cold Hardy Vegetables" is an article I ran across yesterday and since a big cold wave is running across the country, I'm posting this in case it's useful to anyone. It's a great article written by Pam Dawling on the Sustainable Market Farming site.

https://www.sustainablemarketfarming.com/2021/04/14/winter-kill-temperatures-of-cold-hardy-vegetables-2021/

Just thought I would mention that my favas here were blackened and killed completely by frost, when the brassicas only wilted a little and then kept on going. That surprised me because I thought favas were hardier.

Thanks @GoDawgs, very helpful article.
I’ll be covering my favas in addition to a few other things.

Some of those lows they give are way below the ones I've found they can survive. Maybe they mean actual killing temps, and I'm thinking die back temps? The Tatsoi was always the most cold hardy for me, which I figured was because they are very low to the ground, and fairly tightly leafed, compared to most of the other taller, loose leafed greens. They would survive into a brief, but not sustained, low of 18 or 19. Looks like I'm getting even lower than that next weekend (2 nights at 16°), so I'll be cutting back all of my greens and pulling those snow peas and sugar snap peas (they have already stopped producing). I still have some covered, but that's all.

Good article.

For the first time ever I covered my leaf lettuce and I don't know that it's growing much but I figured that this cold snap would end it so I was able to pick enough to made salads for Christmas Eve dinner.

December 2022 by Brownrexx, on Flickr

There just seems to be a huge difference in the effect of frost depending on other factors, like how warm the ground is, how wet, etc.

We had a frost in early october that was "heavy hoar" I mean everything was covered in white. I expected squash and buckwheat to be completely killed, but actually it was the upper canopy that was covered in actual frost, that was killed. The plants lived on below that cap of frost. Squash plants even produced a few more in the weeks after! (I cut off the damaged leaves, which otherwise would've rotted everything). I put it down to the soil being extra warm from the crazy hot summer we had.

In another patch, the buckwheat was sown later with some daikon and mustard. Small plants of buckwheat killed outright by frost, but the young daikon has been looking alive every time I've checked, in spite of numerous frosts and days of light snow cover. Eventually some rodent started nibbling on the leaves, but they may still be green out there today.

There's still a somewhat wilted old psbxkale in a pot by the back door, that looks like it would revive and grow new leaves, and the Yod Fah was amazing after bearing tons of seed, they were shooting out new flowers as soon as a frost passed, all fall. They seemed to hate a cool breeze early in the spring but boy they got hardy when full grown.