A broad category of clay bodies fired below 1200 degrees Celsius. Because it never reaches vitrification, the fired clay remains porous and must be glazed to hold water. It is prized for its plasticity during throwing and its ability to take bright, low-fire glaze colors, though it chips much easier than stoneware or porcelain.
Heard on the job
The terracotta planters are just unglazed earthenware so they'll breathe and let the roots dry out.
Insider tip
Since it remains porous, leaving an unglazed earthenware pot outside in freezing weather will cause it to crack as trapped water expands.