I used to have these plants growing in my dorm room. I needed to add some more herbs to my collection, so I dug up most of the previous plants, took the soil from the pots, and mixed it with home depot potting soil. I watered them like normal and found this white stuff growing all over the top of the soil and on the pots. I'm guessing mold but I have no experience with plants so I figured I'd ask first.

I'm wondering what this white stuff is, if there's a way to get rid of it, and what's the best way to prevent it from growing again?

White spots on a pot White specks on soil Mesh white stuff over soil Weird white clump near rim

  • How long have you used this terracotta pot? Does the white stuff on the outside feel gritty or organic? Dec 31, 2017 at 18:31
  • Looks like just salts. Especially Calcium salts. not a problem. Jul 5, 2020 at 12:10

1 Answer 1


Definitely Mold spores, my suggestion to you would be to ditch the current batch of soil and any remaining from most recent purchase and buy bag of new reputable brand potting mix. I venture to say that it is not appearing on the outside of the blue glazed pot?, but is the moisture leeching through the un-glazed terracotta. Firstly allow the pots to dry out in sun for a good few days (this is to allow the Terracotta to dry out) then take each of the pots and soak them overnight in a bucket of white vinegar or bleach solution (this is to kill mold spores inherently leeched into the porous terracotta) Allow the pots to dry thoroughly before you start the process of replanting. Given the porosity of terracotta, you could (if you want) paint the insides of the un-glazed ones with Bondcrete, I am in Australia so not sure of branding, but it is a waterproofing membrane to stop moisture leeching through brickwork, or a co-polymer floor sealer would probably do just as good. In essence both are just liquid plastic (for want of a better word). I hope this helps May I suggest slightly less in the watering department and remove excess water from tray after about an hour as any excess moisture will only help promote molds

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