Keeping Mold Off Clay Pots - Knowledgebase Question

Lillian, AL
Avatar for michey
Question by michey
May 18, 1998
I have planted a variety of plants in old clay pots. I let the soil dry before watering but I have a constant band of mold on the pots. The pots are outside so ideally the sun would prevent the mold but it's very humid. I don't have time to scrub the pots every couple of weeks, nor do I want to invest in new pots. Do you know a way of keeping the pots pretty?

Avatar for lawrensarthur
A comment from lawrensarthur
September 30, 2017
Try water and chlorine bleach @ 50/50 in a 5 gallons bucket and let them soak for several hours. Then scrub w vegetable brush and soapy water. Be sure to rinse well before using them.

Name: Debra Coury

Avatar for dlcoury23
A comment from dlcoury23
September 30, 2017
Try using Dawn dish detergent & water (50/50). Allow to sit several hrs. brush off. I use this on our flagstone which is in humidity & doesn't get enough hrs sun each day to keep mold from growing

Answer from NGA
May 18, 1998
Part of the beauty of terra-cotta pots is the character they develop as they age. Some of this character is in the white streaks and green mold that they develop. Since terra-cotta is porous, moisture is constantly being drawn from the soil to the outside of the pot where it evaporates. This is good for the roots of your plants but it also sets up just the right environment for mold to grow. The mold is relatively harmless, and outside of sealing the pots inside and out, there' s no real way to prevent it. You could put your plants into plastic containers and place those containers into the terra-cotta pots. That way the decorative pot will remain dry and free of mold.

Name: Phillip williams
(Zone 7b)
Answer from phillipawill
September 30, 2017
As a microbiologist, I might suggest that since your pots are exposed to the sun, at least part of the day, and given the speed with which the discoloration seems to reappear after washing, that what you may have growing on your pots is not mold but algae. Algae is always some shade of green. I know of nothing that you can use to prevent algae or fungal growth on your pots (for any length of time) which could not also possibly harm your plants. The use of a chlorine wash on an empty pot will work, but only for a short time until nature reinoculates the pot.

Name: Greg Bogard
Winston-Salem, NC (Zone 7a)
Avatar for Sscape
Answer from Sscape
September 30, 2017
I agree with NGA about the look of old, weathered pots. However, if you reuse these pots, and there is white, slimy mold on them, it would be best to wash that mold off. That kind of mold can run rampant and cover the roots of your plant. That would not be bad except for the fact that the mold waterproofs the roots--so they can not absorb water. Your plant will die from dehydration. The best way to get rid of that mold is the first suggestion: 50/50 water/ chlorine bleach. After the soak and rinse---let them soak in straight water for an hour or two to get the rest of the bleach out---then let them dry completely before you use them.

Avatar for micharo
Answer from micharo
September 30, 2017
As others have said above, it's the nature of unglazed terra cotta. If you want a cleaner look you should go with glazed pots.

Avatar for alfredenewman
Answer from alfredenewman
October 1, 2017
Perhaps you could try sealing the inside of the pots

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