I'm in Eastern Ontario zone 4/5 and we often get wickedly cold, bitter winters with lots of snow. I'd like to know if I should dig these plants up, or just leave them overwinter and cover them with lots of straw. Maybe it's too late to dig them up, though the roots seem rather close to the surface. Right now the ground is frozen, so I would imagine no digging would be possible, but it's supposed to warm up a bit in the coming days. (Rain, and wet snow). If they were dug up at some point, when should that be (as in, what's the point of no return when the cabbage would be damaged by the cold?), and would they be stored in a cold, dark shed, covered, and/or pruned? Or would they be potted and put in a window like Geraniums? Thanks for any input.