Unglazed pots make great planters because they absorb water from soggy soil. Over time this extra water will evaporate and function as a kind of air conditioning for the plant in summer. While this is ideal during hot weather, it is a disaster during winter. Make sure you clean and store these pots inside a garage during winter.
Glazed planters are often glazed on the outside, but often not on the inside or underneath. If you have not used a second, smaller container inside the pot for the plants and the pot is filled with soil, we really recommend you to always keep these pots elevate and move them indoors during winter.
Completely glazed pots are easiest for upkeep. Almost all of our antique glazed pottery was traditionally used as rice wine containers and were fired at high-temperatures. This means they had to be able to withstand ice cold weather while the wine was fermenting. If you remove all water and cover the pot, then these pots should be fine during winter!
Our experiences with antique pots
Because most of our pots are antique, we cannot guarantee that pots won’t sustain winter damage. But in our experience, the quality of our pots are high enough to withstand wintery temperatures. We have many antique pots in our own garden for more than 15 years; glazed and unglazed, without plants, or used as planter with an easily removable second container. We take the steps described above to take care of them and, in all those 15 years, not one pot was broken during winter or other extreme weather you can get in Western Europe!