I was surprised that the leeks didn't survive. They are there but they are very mushy. When I tried to pull one up, even after loosening the soil under it, it just broke apart and left the mushy top in my hand. I did not mulch the leeks and I don't think that I did in prior years. I know that we harvested a lot of leeks after winter last year. I suppose the cold, cold weather just did them in.
A Google search brought this:
In colder areas, extend the harvest season by mulching deeply around plants (up to 1 foot deep) before a hard freeze. You could continue harvesting leeks until they are locked frozen into the ground, but don’t let that happen. Dig them first and store. Freezing would be the method of choice - a minute of blanching first.