Well, I waited too long and the temperatures dropped down into the 20's Fahrenheit. The tops of our radish crop were frozen to mush. Most looked like they still had live growth at the center, but when I cut two "rejects" for dinner they had frozen areas in the root itself. I'm crossing my fingers that some of the "selects" will be okay enough to replant in the Spring for seed production. The "selects" are the most pigmented ones. Here are some examples of rejects that (although poorly shaped and sized) still had the coloring I'm shooting for.