They're not as hardy as regular cabbage, but I wouldn't worry about covering or harvesting until the weatherman says it's going to fall to about 27/28.

We usually hit 24 or so degrees every year, 19-21 degrees every few years, and between 15-17 degrees every 15 or so years, and our winters are usually really wet, if this information helps!

@6:00 am this morning it was 26 and dropped down to 25 right at sunrise. Thank goodness it did not get down to the forcasted lows, I just checked on my citrus trees and it looks like the frost cloth saved them so far, and my blooms look alright too. It is above freezing as I write this, just one more night and it will begin to warm up.

They are supposed to be very hardy, so I'm guessing being dry may have been the cause. Anyways there is residual snow from christmas until usually the middle of March here so I really doubt dryness will be an issue. My plan is to use either leaf bags, dried leaves with a tarp over them or just dried leaves since the snow insulates pretty well. I am aware that with most plants, their first winter is their toughest, especially if they are growing in pots. Were the pots buried into the ground at all? If you left the pots simply sitting on top of the soil without burying them into the ground, that will cause the root balls to freeze which restricts the water to the plant. The only exceptions I've seen are fruit trees, blueberry plants or alliums which don't seem to mind getting their roots frozen solid.