I would if I were you. The collards will likely survive regardless, but a little insulation would help to guarantee that. That's probably marginal for the mustard greens and broccoli unless they're a particularly hardy varieties (someone correct me if I'm wrong). I've successfully overwintered all of these under Ag-19 row covers here in NC for the last few years, but when temps drop into the teens I've always added an extra layer of row cover just to be safe.

Thanks for your quick response.

The collards will survive easily. The other ones I am not sure and I would guess that they will die.

The mustard greens should be fine if covered. Not sure about the broccoli.

I just harvested savoy cabbages--while they can take it down to 10 degrees, we're expecting 10-15 below zero. Hasn't been that cold here in well over 20 years.

zachey, while it's probably too late for you to make some tunnels they really are the best types of covers. I've started using EMT for frames and will be expanding my use of them late this winter/early spring.

I started experimenting late fall trying to keep rosemary outside. First I had the small tunnel then added the larger tunnel. I wasn't confident enough to keep my 2nd year rosemary plants alive during the deep freezes we've had so far this winter so I moved some of them inside and the rest to the old school coldframes.

So far this is the best tunnel that I have.
{{gwi:12342}}

Those crops will survive the cold, but they will come back better and faster when the weather warms if you cover them. If you don't have a plastic cover, just cover them with newspaper or cardboard weighted down on the edges. If they get wet, no biggy they will still protect your plants.

For future reference... we too experienced the cold. On 2 consecutive days, temperatures reached 19 deg F lows and we were below freezing for 18 hours each day. Broccoli, cauliflower Brussels Sprouts all survived. However, the cauliflower leaves do look a bit droopy and the plants may take a bit longer to recover.

This post was edited by grandad on Fri, Jan 10, 14 at 13:39

Single digits Tue. and Wed. here. 4F. My turnips and mustard greens are yellow but still alive after we finally UN-thawed. My collards are droopy but still green.

I didn't/couldn't cover them because the cold snap kept me at work all day preparing for it and repairing the damage later there.