If we get a light overnight frost, I'll re-cover them. If we get a deep freeze, I'll put them in the garage overnight. I've had wintersowing years when my seedlings lived in my garage for days at a time. I've had to park my car outside in the cold, sometimes snow...
Most years, this stuff isn't necessary. Mother Nature tends to handle things well without much intervention from me. This is my 7th year wintersowing, and I guess if you do it long enough, you see it all.
What was I thinking sowing all this stuff? I don't think I have space to plant half of it if it grows
A lot of the seeds were pretty old, and in some cases I only had a few seeds, so when all is said and done, I guess it might not be all that much.
Karen