Comfrey in zone 4b

Howdy All! I am new to the forum, and somewhat new to permaculture. I am working with a small 1/10 of an acre bacon strip urban lot in Northern NY. This past winter was a killer, with no less than two polar vortexes, bringing actual temperature down to -30 F before wind chill was factored into the equation. I don't think that soil temperature got down quite that low, being that it was buried under more than a foot of snow and ice. Anyhow, everything that I have read on comfrey suggests that it is only hardy to -15 F, so I would not be surprised if the climate up here is too cold for comfrey to overwinter as a perennial.

So, I have two questions:
1) Will comfrey seeds will survive the winters up here? The USDA says that I am in hardiness zone 4b.
2) Will comfrey started from seed have a long enough growing season to be viable? This year, the ground was covered with snow until April 9th, so if the conditions of this past winter becomes the New Normal (good Lord I certainly hope that it doesn't!), I will have a growing season of maybe 5-6 months before everything is buried under snow again.

I'm in zone 1b and it seems to do pretty well here without any parka.

My mother grew it from seed as an annual every year in solid Zone 1, winter temps to -70 and outdoor growing season from May 15 to Sept 5 or so. She grew enough to dry and make poultices and tea. However I don't recall her ever getting seed from it, though she might have; I was just a kid and hated the garden for the most part because garden equaled work.

Thank you everybody. I new that snow insulated the soil, but I didn't know how well. I am going to start with the Russian Hybrid this year, and if it works, I will probably try 'true' comfrey next year.

It's made a couple winters here in Fairbanks for me...hopefully will be coming up again soon, now that the snow's melting.