i'm probably in a similar zone as you call it, i am in sub-tropical where we get frost in winter, the frost can get heavy but generally no worse than medium and not every day av' a few days in a fortnight period.
over winter i grow the brassicas, pak choi, loose leaf lettuce, potatoes, onions, garlic & mustards grow all year here if frost stay on the light side to medium we can keep tomatoes going all winter.
