Great link, thanks! This is on my "to-do" list for 2009. :)
Rosemary

Here in central SC you can usually grow collards, spinach, snowpeas, and green onions just out in the open. I forget the situation with onions, but every number of years the collards get wilted by cold, and at least a few times in 30 years I've seen snowpeas and spinach get hit.

I left my broccoli plants in the ground when we had our first frost...hadn't got anything out of them and wanted to till in some leaves to set up the soil for the spring. Well, they made it through that first frost, and the second...and are even now green and perfectly fine. By that I mean that while they're obviously not growing, they are not dead either. Surely this can't be normal broccoli behavior?...tolerating 9 degrees F? Should I leave them in the ground and expect them to produce in the spring?!

if they look like they're fine, i'd leave them in for sure. i've seen ornamental kales and cabbages go thru similar temps w.o protection, so why not broccoli? If some of it looks damaged, i'd still be inclined to leave it in.