If it warms above freezing during the day, but below freezing at night, the constant freeze-thaw would be bad for the plants..
The porch faces south, and it does the constant freeze-thaw all winter. I'm thinking that the porch is out.
The basement sounds more promising to me..is it heated?
The basement is not heated. It's a steady, cool 50-ish degrees year 'round. It's a dug earth basement (original to the house, which was built 150 years ago), very dark, very damp. There's a furnace down there, but it's never used, because I had a pellet stove installed last year, so the basement temperature never fluctuates.
So, cut the pitchers, rinse with rain water, sphagnum, bag 'em up and stuff 'em in the basement. Yes?