This year I planted 4 artichoke plants - 2 violettos and 2 imperial stars. The violettos didn't produce anything, but one was in far too shady of a location. One imperial star produced, but the other didn't.

I've moved some plants and the neighbor trimmed her tree, so I'm optimistic that next year will be better - if I can overwinter the plants. That's the challenge (the seed company states the Violetto is zone 6+ but I don't believe it). I'm in Ann Arbor, Michigan, and think these plants need some TLC

I've seen some people say leave the plants out and exposed until after frost and they start dying off then trim to a few inches above ground. Then mulch, cover with a box, and mulch more.

Last year I kept one alive covered with a clear storage container and a string of xmas lights, and am frankly more optimistic about this route - especially when the weather drops into single digits.

What do you think? How low can the temperature go before I need to supplement? 30? 20?

Or am I better off just mulching like there is no tomorrow?