Even though the patina on a terra-cotta pot -- whether it's encrusted with whitish salts or a smattering of lichen -- may be beautiful, you will provide a better growing environment if you sterilize your pots. Sterilizing pots rids them of the bacteria, fungi, or diseases that are present.
How to Sterilize Terra-Cotta Pots
1. To prepare terra-cotta pots for planting, soak them for several hours to overnight in a solution of ten parts water to one part bleach. Always wear gloves when working with bleach.
2. After the pots have soaked, scrub them inside and out with an abrasive sponge or brush until the patina is gone. Rinse off any residue. Your pots should now be as good as new.