When deciding what type of container is best for growing your plants, you’ve probably at least considered traditional unglazed terracotta pots. They’ve long been a staple of at-home gardening, and for good reason: They’re relatively inexpensive, can be reused, and are porous, allowing for an exchange of air and water.
But they also have a tendency to develop white stains on the outsides of the pot. And while some people consider that part of their rustic charm, others find the film unsightly and want to get rid of it. Either way, here are a few ways to remove the white residue from the insides and outsides of terracotta pots.
What is the white residue on the outside of terracotta pots?
The white film or crust that forms on the outside (or inside) of clay terracotta pots is soluble salts. Hard water (which includes most tap water) contains salts and minerals. When you use it to water your plants and it eventually evaporates, it leaves behind these salts and minerals as a white residue — kind of like what happens on shower heads.
Meanwhile, if you have softened tap water, you can still see that white stuff on the outside of your terracotta pots. But in this case, it’s likely caused by your soil fertiliser, which contains minerals. Because these clay pots are porous, the minerals from the soil seep through the pot and can appear as residue.
How to clean the white reside from terracotta pots
If you really want to thoroughly clean the pot, your best bet is to do it when the pot is empty. Otherwise, depending on the condition of the plant, you may want to consider removing it from the pot for the cleaning process — especially since there are probably also soluble salts on the inside, too.
Here are three common methods:
Make a solution of one part vinegar to 20 parts water. Soak the pots in the solution for about 30 minutes, then scrub any white spots and residue. Rinse thoroughly with plain water, then allow the pot to dry.
Make a solution of one part bleach to nine parts water, and use it to scrub the inside and outside of the pot. Rinse thoroughly with plain water, then allow the pot to dry.
Make a paste of baking soda and water and use that as a spot treatment to scrub off the white residue.
Is it OK to leave the white residue on the pot?
While it’s always a good idea to remove the white film that forms on the inside of a terracotta pot (to prevent the soluble salts from getting into the soil), leaving the residue on the outside of the pot is generally fine. According to an article in Horticulture Magazine, “salts on the outside of the pot will not harm the plant.”