I'm in N-Va but 7a, pretty much all cool weather crops can be planted starting next month (or late this month). I grow and overwinter kale, carrots, radishs, leeks, scallions, and garlic super successfully, I put put a layer of fall leaves to insulate the lower stem of the plants and as long as you protect the soil so no freeze/thaw-heave, they should do fine. I have done broccoli as well, those are into their less productive secondary head production. I also plant cabbage and collards sometimes (super hardy like Kale). Mustards and Bok Choy can
make it through mild winters with protection (covering and at freezing
temps). Wet soil that freeze/thaws/heaves tends to kill what I've tried to overwinter. So from that perspective, hard covered (plastic) is good when a snow, sleet, heavy cold rain will melt/soak and then freeze. If you soil has really good drainage, then this is less of a problem. My clay amended with compost sometimes holds too much water, so I've had the problems when we've had inches of snow that melts in the day for a week or two and refreeze and the lower soil never thaw to drain.

Thanks fruity paws. That’s very helpful. I had not considered the freeze/thaw cycle. So this happens with all overwinteted plants, not just root crops? If so maybe I will just put all the cold hardy stuff under plastic instead of row cover, and keep it vented all or most of the time. Then I could put some less hardy stuff under plastic and keep it closed on cold days. I plant in raised mounds of Amended clay and i think it does freeze solid sometimes.

Even super hardy (Russian Kale) has died on me when I let soil get wet (either due to cold rain or snow melts) then freeze/thaw. I have found that if I keep the soil moisture under control, I can get plants through. A multi-day freeze thaw event causes more heave and more root tear. The long hard freeze (without thaw) of the polar vortex, I've had leeks and kale make it through. Cloth does better protecting from the cold. I put plastic to keep precip off or if freezing winds will be there (prevent frostbite), though if you do us auxiliary heat (like an incandescent bulb), plastic hold heat in as well.

I find that each winter seems to present different challenges (snowmageddon crushing things, polar vortex, sleet storms), so be ready to adjust.

I'm in Maryland (7a) but was outside Richmond for over twenty years. I find that my fall-planted onions grow much larger than my spring-planted ones, even though most of the planting maps say we're too far north for fall-planted onions. And everything Fruity Paws said is right for the area. This year I'm trying a variety of bok choy called winter choy that's supposed to be extra cold-hardy, and I'm going to leave some out unprotected to see how it does. I also don't bother protecting my kale. The curly kale pretty much always makes it through the winter for me (even in containers that go through multiple freeze/thaw cycles when the ground doesn't freeze) whereas the smooth-leaved varieties don't do as well (so I just eat it all around the beginning of January).