According to the “Eat the Weeds” website: Depending on how cold and how much snow there are quite a few edibles possible in winter. Sorrel can often last through a mild winter. Some radishes and wild mustards can take quite a freeze and stay alive.
Hardy little chickweed can germinate under snow so when the spring melt comes it is among the first green plants.
An info rich website: via Winter Foraging | Eat The Weeds and other things, too.