Posted: 07/11/2012 at 20:10
We grow a huge number of things in pots, and find that it is far more the pot that you need to protect rather than the plants. I had camellias in very large clay pots for several years untilt he very hard winter of a couple of winters ago - then lost them - well, it did get to -25 so not surprising really.
I don't use bubble wrap because it catches water between the bubbles and these hold water which then freezes, Newpaper, hessian, fleece, old curtains - whatever is absorbent and warm for the few that really do need it. Of the list erhat you gave, I would say all are fine outdoors - if it gets to below -15 then a bit of fleece will protect the pots. We have 65 hostas in pots, and although we have lost the odd pot, rarely a hosta. Tulips I regard as annuals now, plant now, enjoy in spring then do it again in autumn - daffs last longer but eventually give up in pots.
Clay pots will stand alot, but glazed ones will give up if there is any sort of crack in the glaze where water can get in & greeze = yjod eill then push the glaze off the pot. Plastic pots get bitterly cold, and I would rarely use them out of doors in the winter. The new resin pots seem good, though I have not had a great deal of experience with them yet.