From my experience that overwintered stuff gets tough, bitter and earthy tasting. However, chickens will eat them.

It's heart breaking to hear and see. We didnt have much of a winter the previous two years and I lost three garlic varieties and one (ajo rojo) hanging on because of a lack of storms.

Some nice nitrogen ingredients for the compost :-) That's how I justify tossing anything in the garden that's still green.

When I've had lettuce over winter, it has started out very small and turned into nice little heads. You should get some good mustard greens but I agree lettuce is probably going to be tough. I would try cutting it off to see if base re-grows as tender heads.

You could try cutting it at the base and see if it grows back, why not right?

It is not a negligible difference what "+2 zones" looks like same time of year; can't wait to be there! :)

Still, even in 4b, I have some spinach that has survived winter so far, including a few bouts of -25°C. Some plants were under cold-frame, some under snow. I don't think I'll be keeping these plants though, but will be transplanting seedlings I'm in the process of starting indoors.