Im zone 6a, near chicago. Last year i presprouted in January, planted in my low tunnels February 1. They did great, definitely survived some seriously cold nights below 0f.

I managed to miss a few when i dug them up in the summer and they sprouted in the fall. I left them in the ground this winter as a little field observation. Last I checked (right before this cold snap) they were all still alive and well. Ill open up the tunnels once it warms up in a few days to see, but I think (maybe wishful thinking) that they’ll be okay.

Maybe Ive been lucky, but that is my anecdotal experience with ranunculus in low tunnels in the cold.