Two years ago we planted artichokes in our garden. This is their first winter as mature plants. They've put out side shoots which I want to separate, but I'm nervous about it.

Last winter the plants died back when the weather got cold and didn't grow again until spring. I thought that was normal. This year they died back too, but then they started growing again. Now it's a week before Christmas, and the plants are two to three feet tall. Our recent frosts haven't fazed them a bit.

Is it safe to divide these plants while they're growing? If not, what can I do?