Great article! I have several concrete urns, but am unable to bring them into the house or turn them over. I live in zone 5a. Because of the danger of ice collecting inside and expanding, thus cracking the urns, I put styrofoam peanuts inside before adding dirt for my plants. In the winter if water accumulates, freezes, and expands, it will crush the peanuts before exerting pressure on the concrete. Several of my urns have seen many winters and have not cracked yet. A local statuary store suggested this, and their customers have had good results also.