Unprotected, they normally croak at 20F, and guess what, it hit 19F this year in Seattle. I am not utterly sure mine are dead, but I don't see any shoots coming up. Normally they are evergreen, and with relatively mild winter temps AFTER the killer freeze, they should have shown up by now.
Yerba Stella, supposedly extremely hardy, also MIA.
One thing that went wrong was that there was no snow cover and the ground actually froze. Killed a lot of things not used to that. Another thing that goes wrong is that our winters are normally damp, and freezing weather followed by mild damp weather makes a lot of things ROT. Sometimes things will survive at first only to be killed as the rot goes down into the ground and kills the bulb/root/tuber/crown.
I have a variety claimed to be coldhardy to 0F, which does not sound credible, but if it is any coldhardier than other varieties, I'll give it a shot. Also supposed to not require "vernalization", meaning that it can bear the first year from seed if started early. I've got 3 seedlings sitting in the hoophouse. The variety is called "Emerald". It's an F1 hybrid, supposed to be vigorous and productive.
Artichokes by the way are quite attractive plants, like gigantic blue-flowered, "architectural"-looking thistles. Some people here grow them as ornamentals in their perennial borders.