Pots made of clay or concrete are more likely to withstand freezing weather in the cold winter months without cracking if they're sealed on the inside.
Here's what you do.
Coat the inside walls and bottom of the container with a paint-on roof coating (not to be confused with roofing bull). Use an inexpensive paintbrush with nylon bristles to apply the coating.
Let dry thoroughly before filling coated pots with soil and plants. Your pots won't crack and it will give them a longer lifespan. It will also slow down the salts from making their way to the exterior of the pots so they won't turn " salty white" as quickly.
Pots made of clay or concrete are more likely to withstand freezing weather in the cold winter months without cracking if they're sealed on the inside. 
