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Mold on Clay Pot?

Posted by Sugi_C 10a - SF Bay Area (My Page) on
Mon, Mar 11, 13 at 18:19

The first photo is on the day I repotted this ficus on March 1.
Growing Ficus

A little back-story:

This pot, which I actually like a lot, originally housed my Calathea -- which has been my most problematic plant this season (which eventually just required a drastic soil change and repot into a much smaller pot). As none of the problems were disease-related, I simply washed the pot with soap and water -- and let it dry. I did notice a lot of salt accumulation white marks on the bottom half of this pot when the Calathea was in it.

The size was nice for my Ficus so while changing the Ficus to gritty mix, I grabbed this pot to house the plant. As mentioned, that was March 1.

Come March 8 -- I took an update photo.
March 8, 2013: Rubber Plant
I didn't notice it when I took the photo, but you can definitely see the beginning of mold.

On March 10, I was watering the plant when I noticed a significant amount of fuzz and peering in, I spotted the mold.
Given my clean freak side -- my immediate action was to run for a paper towel and wipe it clean, then run for another with a few drops of pure bleach on it, and wipe it clean again.

And then, I sat there --- with the question of why/how there was mold on this container, and only this container, inside my house. It only occurred to me then that I should have taken a photo of it first; it's not like it was going anywhere.

Anyway, I forgot to post yesterday to ask this question -- but today, it's back -- photo below. It's milder than what I cleaned off yesterday, looking like a layer of dust that's piled on for months, but unless only this container is collecting all of the dust in this city -- the mold is growing back. This is in spite of the bleach I cleaned it off with!

Anyone have experience with what might be going on? I can easily chuck the pot, yes -- and I have triple-checked all of my other clay pots and there is no dust, mold or fuzzies on any of them. It's just this one pot.

Follow-Up Postings:

RE: Mold on Clay Pot?

How would I handle suspected mold About the same way I would handle mold if it where growing in my basement Call someone who can determine or confirm and suggest proper mold treatment.
Is that a fiberglass pot by chance ?

RE: Mold on Clay Pot?

It's a regular painted clay pot.

RE: Mold on Clay Pot?

A spritzing of hydrogen peroxide and water, perhaps?


RE: Mold on Clay Pot?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Wed, Mar 13, 13 at 17:37

A few years ago, I was all excited because I found these beautiful drip glazed serving bowls at a Big Lots store. They came in a variety of sizes up to about 3 gallons (packed 3 in a nest). I drilled drain holes in them, and made several dish gardens of dwarf conifers, thinking to enjoy them while small & then turn them into bonsai candidates as they grew and were transplanted. I notices the same type of fuzzy growth on the outside of these pots ..... and they were glazed with fired ceramic - at least I thought they were. Within a very short time, it became evident the plants were struggling - something I'm not used to seeing. I removed all the plants from the pots and repotted, but they all died. I still wonder what was in the pots that killed the plants. Whatever it was, it wept through the walls, so it certainly would have gotten into anything that was served in them.

A long story, I know ...... and I'm not saying your pots are doing exactly the same thing mine were; but it does LOOK like the same thing I experienced. I probably lost 12-15 dwarf conifers, which frustrated me mightily. ;-)


RE: Mold on Clay Pot?

Josh -

If bleach didn't kill it - would hydrogen peroxide even come close to harming it? I really need to get some just to keep around in case I need it. I was reading on one of these forums that spraying a diluted version onto plants/soil wasn't harmful. Thanks!

Al -

This was the same rubber plant I had emailed you about, if you recall. Incidentally, all those basal stems? I cut 'em off per your advice and now am rooting them, or attempting to root them. :-)
One week post-planting, they're doing nicely so far. Nothing's dead, and all seem to hold back a little when I tug lightly.
Propagating Ficus cuttings
I am curious if those stems will root the same way as cuttings. Not all of them had leaf nodes low enough to actually plant into the soil.... no bueno?

Going back to the mold....
I was envisioning the same fate for it with the pot killing the plant, even though it didn't seem affected at all at this moment, but anything that will grow back from bleach scares me just a little. Hearing your story, Al, and knowing the plants died despite repotting....I'm worried. :-(

So yesterday morning, she got pulled from that pot, and repotted into 5-1-1 in a new pot. I didn't feel like making more gritty mix and I absolutely wasn't going to reuse that mix in the molding pot.

Favorite: Ficus Elastica

Most interesting was that in the last few weeks, it had grown longer roots. I could tell because they were so gloriously white/clean compared to the washed off roots I had planted originally!

BTW, I love, love, LOVE 5-1-1. I'm going to say I usually throw in about a half part more soil than actual "1 part" but something about watering and hearing the soil absorb liquid is very satisfying. The gritty mix DOES actually remain quite moist for a surprisingly long time -- but it doesn't "slurp up" water like the soil. :-) But wow, those clean roots were impressive.

RE: Mold on Clay Pot?

The fungus you see is only a fraction of the fungus that is present. There is likely growth either into the material of the pot (if it is sufficiently porous) or through cracks in the pot and separations between the pot and the glaze.

Swabbing the whole thing down with bleach or hydrogen peroxide will really only kill what is on the surface. As long as there is moisture present and a carbon source you will continue to get more fungal growth. If you want to save the pot your best bet is to let it dry out and then heat sterilize it. Ideally if you get the whole thing to 65C/150F for a half hour or so that should more than do it. The lowest setting on your oven could work and shouldn't effect the paint/glaze even if it wasn't fired on. Just make sure not to get the pot wet while it is hot otherwise it will probably crack.

RE: Mold on Clay Pot?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Fri, Mar 15, 13 at 11:56

You guys are going forward with the premise that it's fungal, but in my case it was a chemical reaction with/between the materials the containers were made from.


RE: Mold on Clay Pot?

That is very true. If you sterilize it and the stuff comes back in a day or two, it is most likely chemical.

In either case it may actually be occurring because of the soap/detergent that you used when you washed the pot. Soap is a surfactant and can disrupt layers of certain varnishes/oils/waxes/etc. used as sealants. A dilute dish soap should be fine, but unless you have a real reason to, I'd wash things in warm water and nothing else.

Al, I'm shocked that those bowls were intended for use with food. If it killed your trees it couldn't have been good for your body! With all of the reports about lead and other nasty stuff being used to make toys I guess I shouldn't be all that surprised at toxic serving bowls.

RE: Mold on Clay Pot?

  • Posted by Sugi_C 10a - SF Bay Area (My Page) on
    Fri, Mar 15, 13 at 16:43

Rhino, thanks for the suggestions on how to fix the issue. I chucked the pot out, though -- but good to know for future reference.

There are too many pots in the world for me to deal with one strangely odd one that grows fuzz. I give myself enough issues experimenting with plants, haha, and creating problems WITHOUT a mold issue!

RE: Mold on Clay Pot?

  • Posted by tapla z5b-6a mid-MI (My Page) on
    Fri, Mar 15, 13 at 18:06

Rhino - exactly what I was thinking about potential toxicity to humans.


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