When sourcing large ceramic pots, the firing temperature is the most critical factor. Ensure the supplier uses high-fire stoneware or porcelain (fired at 1200°C or higher) to ensure frost resistance and low porosity. For outdoor durability, the water absorption rate should be less than 3% to prevent cracking in freezing temperatures. Additionally, verify the glaze thickness and lead/cadmium content, especially if the pots are intended for edible plants, ensuring compliance with FDA or REACH standards.