10 very cold hardy vegetables (zone 3a!)

I would add one more. Mustard greens are tough. Even when the plant completely freezes, the leaves can be used. They resume growth at only slightly above freezing. Low light levels are more of a problem here than freezing is. Mustard grows in dull conditions that most plants don't survive.

I would add Jerusalem Artichoke and ground nut since they can winter in the soil and be harvested if you can dig them up.