White crust on pots

GzhaFebruary 3, 2014

Has anyone seen a white crust on your pots? Any ideas what this could be?

I've noticed some on two 12"-wide pots. They're almost like snowflakes in appearance. It turns to a dust if you touch it.

On one pot, it appears like a horizontal band on the middle (fattest) part of the outside of the pot. But it also runs along the interior of the top lip (not in contact with soil).

The close-up photo (which is the interior of the top lip) shows about 3 inches width. Btw, those black spots you see are part of the design. It's just the white crust that's of concern.


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Here's a second photo.

    Bookmark   February 3, 2014 at 1:00PM
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tapla (mid-MI z5b-6a)

Several years ago, I found some large ceramic serving bowls at Big Lots. They were very attractive, with a nice drip glaze on them, and came in sets of 3 or could be purchased individually. I bought several sets and a few from broken sets, then drilled holes in all of the bowls. Our bonsai club was having a fund raiser, so I purchased 4 lots of 20 dwarf conifers to sell at an art fair. I potted up the bowls with 1, 2, or 3 dwarf conifers, depending on their size, I did this in late April. I also kept a few of the conifer dish gardens for myself.

As the art fair became a memory, I noticed that none of the conifers were doing well - at all! In fact, all seemed to be dying. On examining the bowls I noticed there was some saort of material weeping through the walls of the bowls. I thought that very strange, for 2 reasons. The first was, I assumed that because the bowls were glazed ceramic, they would be impermeable to gas and liquids. I was obviously wrong on that count. The second thing that struck me as strange was the fact that something phytotoxic was used in making the bowls. It's possible that what was poison to plants might also be poison to people, and had I used these as serving bowls might never have noticed what was coming through the walls of the bowls.

End of the story is, I lost all of the plants I had in the bowls, even though I flushed the soil and repotted into terra cotta. These weren't cheap plants, either. Even at wholesale they were $20 each. My main concern was for the poor people who bought them at the art fair. I had no way of knowing who they were and have always felt really guilty about that whole deal.

It's possible that the material forming on the walls WASN'T phytotoxic, but did affect the pH of the soil significantly and in doing so killed the plants - I'll never know. Big Lots wouldn't give a refund, BTW.

All that to say I'm not really sure what's on your pot. I'm not sure if it's precipitants that were once dissolved in the soil solution and were deposited there after the soil solution made its way through an unexpectedly porous glaze, or if it's a chemical in the clay that attracts moisture from the air and forms chains of crystals like you're seeing.

How long have you had the plants in them? Are the plants doing ok, or do they seem to be suffering?


    Bookmark   February 3, 2014 at 5:39PM
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Wow, that's pretty scary. Now I'm even more glad that I made the decision to place plastic pots inside glazed ceramic pots instead of placing my plants directly into the ceramic pots (it was more because all I can find is ceramic pots that have non-removable saucers... was creating drainage issues). I guess that's the "anything to make a buck mentality," even if it has the potential to be hazardous.


    Bookmark   February 3, 2014 at 6:10PM
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Hi....I know that you really have to watch out for pots and dishes, ceramic things that have lead in them.....I have heard of people buying coffee mugs and other dishes that contain lead...ceramic and glazed dishes and pot from other countrys can contain lead....I remember when I did ceramics if I did dishes or anything that was going to be used with food had to be glazed with a different kind of glaze that did not contain lead...could lead in the glaze on your pot cause this??? totally just a guess here....linda

    Bookmark   February 3, 2014 at 8:33PM
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The plants in both ceramic pots are inside plastic pots. One plastic pot fits snugly inside the ceramic pot, so the walls touch at least at one point (but most of the ceramic pot is fatter). In the other pot, the plastic pot doesn't touch the walls of the ceramic pot at all.

They've been in the plastic pots since we got them from the store about 4 years ago. They have been undergoing a slow death since then. Dying leaves have outpaced new leaves. Thinner and thinner foliage. One is now dead. But my guess it's due to inappropriate lighting and/or watering.

    Bookmark   February 4, 2014 at 11:51AM
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tapla (mid-MI z5b-6a)

Read through the link I'll leave below and see if anything about the way you're caring for your plants jumps out at you.


Here is a link that might be useful: An overview

    Bookmark   February 4, 2014 at 9:54PM
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