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How to Prevent Heavy Metal Contamination From a Pot?

I bought some large, used oil vases that I want to use to grow herbs. I am concerned about the old paint and whether the clay might have some heavy metals. Is there a good way to line the inside of the pot in a way that would minimize soil contamination by the paint and clay inside the pot?



Comments (26)

  • war garden
    last year

    try having them tested first

    westes Zone 9b California SF Bay thanked war garden
  • ken_adrian Adrian MI cold Z5
    last year

    yes.. pot in pot is just about always the universal recommendation for huge pots ... usually because they dont have a drain hole or some such ...which one would think that if they held oil.. there arent holes in the bottom.. eh ...


    will you be eating the herbs ... if not.. why is this an issue.. just plant in them and dont worry about it ...i mean really.. arent we talking olive oil or something.. who would put chemical oil in a pot like that??? ... do yo know the history of the pots???


    presuming you arent putting some rare plants in them.. just experiment.. if you loose a couple bucks on some parsley.. so be it ....


    i also wonder why you would grow short squat herbs in tall pots like that .... maybe im missing something her ...

    ken

    westes Zone 9b California SF Bay thanked ken_adrian Adrian MI cold Z5
  • beesneeds
    last year

    Depending on where you are and the jugs, think twice about them for planting outdoors. If they don't have holes for drainage, it's likely water would accumulate in the jug. If water accumulates, it could get icky and that can be a bother to drain out after a while. If they held oil, it's likely the inside is less water permeable than raw terra cotta. If you live somewhere a bit on the dry side or the jugs will be out of the rain it might not be as much of an issue. I wouldn't be overly concerned with potential heavy metals from the paint. It looks pretty well off and not much left. But if you have concerns, you can get the paint or perhaps scrapings of the clay tested.

    So, if you can use them, use inserts. You might need to put a stand in or fill in the jug for the insert pot to rest on. You might find an insert pot of the right size to just fit into the top well. Might still be the better part of wisdom to have someting inside for the insert pot to rest on.

    Tall pots like that can be nice for a mini raised bed to trim herbs off of. I bet a lettuce bowl would look good like that as well. Perhaps consider nasturiums since they are edible, pretty, and you can get some that will spill over the sides of the pot.

    westes Zone 9b California SF Bay thanked beesneeds
  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    last year
    last modified: last year

    Good advice here about heavy metal mitigation. An interesting thing to note is that a research paper has just been published on the use of neoprene rubber as a barrier for soil-borne lead. Turns out it doesn't work. It actually absorbs lead and leaches it out on the other side, very effectively. Neoprene rubber is commonly used for garden weed and root barriers and I think even self-watering planters. That being said, I suspect hard plastics will be more impermeable. But a test would be smart.

    westes Zone 9b California SF Bay thanked daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
  • Fori
    last year

    Those pots are awesome!!!!!!!


    (Where did you get them and are there more? 🙂)


    I'd just do the pot insert so I wouldn't need so much potting soil. I think the height makes them great for herbs.

    westes Zone 9b California SF Bay thanked Fori
  • westes Zone 9b California SF Bay
    Original Author
    last year

    @war garden Let's assume the clay and the paint contain some bad things. The question was how I could minimize transfer to the soil.

  • westes Zone 9b California SF Bay
    Original Author
    last year

    @floral_uk z.8/9 SW UK I am open to using plastic pots, but the hard part of that solution would be getting a shape that uses enough of the available space for roots. A plant like Sage gets very large and must have a root system to match.

  • westes Zone 9b California SF Bay
    Original Author
    last year

    @ken_adrian Adrian MI cold Z5 All three pots have holes.

    I will be eating the herbs, hence the reason I am wanting the soil to be food-safe.

    I am growing hanging versions of Rosemary and Thyme, so giving them some vertical room to hang down was my thought. The pots are also decorative and would be easier for a standing person to pick from.

  • gardengal48 (PNW Z8/9)
    last year

    " A plant like Sage gets very large and must have a root system to match. "

    It doesn't have to. I grow culinary sage in a container - and not a very big one - and that keeps the plant size quite manageable and more than adequately productive. And many grow rosemary and bay in containers as well and they get far bigger than any salvia!! Like anything else grown long term in a container, you will have to root prune and repot on a routine basis.

    westes Zone 9b California SF Bay thanked gardengal48 (PNW Z8/9)
  • Fori
    last year

    I don't know anything about those grow bags but I'd be looking at them...

    westes Zone 9b California SF Bay thanked Fori
  • westes Zone 9b California SF Bay
    Original Author
    last year

    @beesneeds Nasturtium looks like a winner for many applications, and I ordered some seeds.

  • westes Zone 9b California SF Bay
    Original Author
    last year

    @Fori I got them at a local estate sale, and I do think I picked out some of the best ones.

  • westes Zone 9b California SF Bay
    Original Author
    last year

    @gardengal48 (PNW Z8/9) Okay, but the point would be that these Genera of plants all do have large-enough root systems that giving them some room would be appropriate. Do you have any thoughts on how you would line the containers or what kind of inserts you might use to give the roots some space to grow?

  • gardengal48 (PNW Z8/9)
    last year

    And I will say again that it is unnecessary to have to accommodate the pot to the root system of the individual plants. I grow trees in containers not much larger than those and some even smaller! Think of it as practicing bonsai but not so extreme :-) Proper and frequent root pruning, refreshing or replacing of the potting media, proper fertilization and judicious top growth pruning are far more important concerns than pot size!

    I would also not be concerned about using any inserts. I doubt they are the slightest bit necessary.

    westes Zone 9b California SF Bay thanked gardengal48 (PNW Z8/9)
  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    last year

    If the large containers don't have drain holes, why in the world would you want to suspend a smaller pot inside of them? You'll just end up with a puddle of dirty water at the bottom. Maybe a deep one. Growing plants over a pool of bacteria-infested water usually isn't smart. It is not hard to drill into masonry or terracotta pots, though it helps to have a masonry drill bit. Don't need many holes. If you ever retire the pot for gardening, and want something that holds liquid, such holes are easy to patch.

    westes Zone 9b California SF Bay thanked daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
  • gardengal48 (PNW Z8/9)
    last year

    " All three pots have holes. "

    Drainage - in this case - is a moot point :-) The focus now is the size of the insert....or whether an insert is necessary at all.

    westes Zone 9b California SF Bay thanked gardengal48 (PNW Z8/9)
  • westes Zone 9b California SF Bay
    Original Author
    last year
    last modified: last year

    @daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa) The pots all have holes. My original question was never about how to provide drainage. The original question was about how do I prevent heavy metal contamination of the soil.

  • floral_uk z.8/9 SW UK
    last year
    last modified: last year

    My main reason for suggesting inserted pots is entirely to do with the difficulty of removing a plant from a narrow necked container. In the past I have ended up smashing a pot to extricate a plant. I do not think contamination is an issue worth fretting about with these jars. I have many terracotta pots and I often use inserts. Both insert and pot always have drainage holes. You need less soil and you can swap plants around easily.

    westes Zone 9b California SF Bay thanked floral_uk z.8/9 SW UK
  • daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
    last year

    Good that they have drain holes. A poster below suggested they didn't, and you didn't say otherwise, at least until the next day, now that I look back. The only way to prevent contamination of the soil by the pots is to prevent the pots from touching the soil. But I still think you'd be smart to get the pots tested. I would think that your local extension would be able to point you to a lab.

    westes Zone 9b California SF Bay thanked daninthedirt (USDA 9a, HZ9, CentTX, Sunset z30, Cfa)
  • gardengal48 (PNW Z8/9)
    last year

    Test the pots if you like. But I think it is an unnecessary effort and expense. Unless the pots glow in the dark, there are not enough heavy metals in concentrations high enough to be of concern. These were originally intended for food storage to begin with. Anything done to them over the decades is unlikely to alter that attribute significantly. Even if painted at one time, that has eroded or worn to the point where it is a non-issue now. And the porousness and the frequency in which terra cotta containers get watered ensures that whatever potential contaminates might have been involved are routinely leached out.

    Plastic may not leach heavy metals but it does leach as well. If contamination of edibles is a concern for you, I would be more concerned about what kind of impact non-food grade plastics used in the garden are having. Phthalates are present in ALL plastics, even food grade plastics.

    westes Zone 9b California SF Bay thanked gardengal48 (PNW Z8/9)
  • beesneeds
    last year

    What size openings are on those jugs? Pick an insert that might be snug to an inch smaller than that opening. You won't need more than 12-16 inches in depth for most herbs. Plastic nursery pots are fine for growing food plants in. Look around at small garbage cans- often those can be drilled for drainage and can offer some different sizes than nursery pots. Many plastics are safe for growing food, look for 1,2,4,5, and avoid 3 and 6 number codes.

    westes Zone 9b California SF Bay thanked beesneeds
  • lgteacher
    last year

    Plant roots grow out horizontally much more tha vertically. You can easily grow rosemary, which I grow as shrubs, in a pot half that depth. Use the pots as cache pots with a smaller pot inserted in tthe top with something holding it up - inverted flower pots or whatever you have handy. You won't have to worry about what metals may or may not be in the clay pots. That's the advice most posters above are giving you.

    westes Zone 9b California SF Bay thanked lgteacher
  • floral_uk z.8/9 SW UK
    last year
    last modified: last year

    The inserts I use have a lip so they don't need support from below. They just rest in the top of the outer container. Something like this. The lip is hidden by the plants and soon weathers anyway.


    You can just see the insert edge in the fruity pot. You can't see it at all in the larger one.


    westes Zone 9b California SF Bay thanked floral_uk z.8/9 SW UK
  • carolb_w_fl_coastal_9b
    last year

    Maybe I missed it being mentioned, but you can place an empty upside down pot inside, before inserting the one you'll be planting in - to support the upper pot.

    westes Zone 9b California SF Bay thanked carolb_w_fl_coastal_9b
  • westes Zone 9b California SF Bay
    Original Author
    last year

    @carolb_w_fl_coastal_9b I was thinking of just putting some bulk lava rock at the bottom of the pot and setting any internal pot on top of that. It would prevent the tall narrow pots from getting top heavy and spilling over.