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Sealing ceramic pot for edible fruit?

Posted by Emerita MN (My Page) on
Sat, Jan 11, 14 at 17:44

I have a dwarf kumquat arriving in 3 days and I am planning on getting a dwarf meyer's lemon soon. We want aesthetic pots because the plants will be in the living room 6 months of the year. I want heavy pots because when the plants go outside and get taller they are at risk of blowing over. Planter availability in Minnesota is limited in January but a farm supply store was selling 13-19" blue glazed pots at a very good price ($8-$15 which is less than a plastic equivalent costs). I bought 5 thinking I could use others for outdoor flower planters until it's too cold for anything to live outside (so slight risk of freezing), and for purely ornamental trees (yucca, ficus). The planters are made in Malaysia and glazed on the outside and upper 1" of the inside, but the rest of the inside is unglazed. They appear baked (temperature unknown), however, when I drop a teaspoon of water on the inside it beads at first but eventually soaks in, so they are not sealed.

Given the unknown nature of the glaze, our desire to eat any fruit produced, a desire to weather-proof the pots not being used for fruit for early spring and late fall outdoor ornamentals, I am wondering about sealing the inside. Will this work? I have read various suggestions for acrylic, polyurethane (spar or regular?), sealant paint used for basements.

What about for sealing pots for ornamentals only?

How about not only keeping water out of the pot material but also potential glaze chemicals out of the soil (and plant, and us)? Safe? There's no way the people at the store are going to know what's in the glaze.

I thought about trying to use plastic pots as liners with the big pots as decorative holders, but then the trees would end up in pretty small pots (10" or so?) for their targeted 4-5' height. The planters aren't suited to nest standard pots.


Follow-Up Postings:

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RE: Sealing ceramic pot for edible fruit?

Unless I knew with certainty that the glaze was stable and safe, I wouldn't put edibles of any kind in glazed pots. Maybe you could seal the inside with something safe (whatever that might be), but, given the difficulty in truly assessing the risk, I just don't see the point in taking any chances with an unknown glaze (either for your health or for the health of the trees).


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RE: Sealing ceramic pot for edible fruit?

How about lining the pots with a heavy plastic bag? That should minimize the loss of volume while separating the pot from the soil in a stable and reversible manner. Put the bag in the pot. Fill w/soil, trim the top, pierce the bottom via the drainage holes, push a few wicks in.


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RE: Sealing ceramic pot for edible fruit?

Or you could use the terra cotta as cache pots and get some really cheap plastic pots to go inside them. This would also make them easier to move as terra cotta full of soil is very heavy. I do this so I can change the displays around seasonally.


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RE: Sealing ceramic pot for edible fruit?

How could outside glazing be harmful. We use all kinds of coffee cups, mugs, dinner plates .. with glazing. !!!

Second : sealing the inside is , IMO, totally unnecessary plus it could actually cause contamination.

JMO


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RE: Sealing ceramic pot for edible fruit?

Pottery intended for food typically uses glazes without lead or other contaminants. I have read that inexpensive pots (these were!) are fired at low temperatures which require special low temperature glaze which may contain lead or other heavy metals. There was a scare a few years ago about cookware from outside the USA using lead glaze. I don't know what's in the Malaysian glaze but since the pots are for plants there's unlikely any control. The pot interiors are permeable (I tested with a few drops of water which soaked in) so I am concerned if water can reach the exterior glaze from inside that there may be long-term transfer of lead or cadmium (which I don't know is _not_ there) or whatever to the inside.

Plastic liner pots is a good idea but it's hard to find ones to fit the containers without dropping in size so much I am losing 1/4-1/3 the volume of the container. I'll hunt around since you are right, it does make them much lighter to move if it can be done as two pieces, but this isn't exactly the best time of year to go hunting for pots in Minnesota!

I bought water-based acrylic finish and painted on 2 layers. I did this to all the pots so they are generally sealed against water soaking into the pottery (I could end up storing empty pots outside in freezing temperatures). For one of the fruit trees I also lined the pot with a piece of old shower curtain so there's now 3 layers between the plant and the pot. At least the plant is happy now and if I can find a plastic liner pot that fits I can transfer it later.


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RE: Sealing ceramic pot for edible fruit?

I'm with seysonn on this one - to a point.

In fact, some cookware and dishes do have lead in them (I read up on a lot of this stuff a few weeks ago when I was trying to figure out a suitable replacement for a pet's water bowl that has worn-off glaze.) and I don't think you're necessarily in the clear even if something is made in the US. Besides, even if you could guarantee your dishware was safe, could you guarantee that items from restaurants, friends/relatives, etc. were?

http://www.dhs.wisconsin.gov/lead/doc/Porcelain and Ceramic2.pdf

And about that shower curtain according to this site (which may or may not be reliable) there are plenty of issues there too: http://watoxics.org/files/VolatileVinyl.pdf

Anyway, my point is if it were me I'd use whatever pot I felt like and pat myself on the back for increasing and varying my fruit intake. In my opinion unless you're already doing everything else you can to be healthy as far as diet, physical activity, and prevention/early detection of health issues then worrying about any negligible risk of lead contamination from pots is a waste of time.


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RE: Sealing ceramic pot for edible fruit?

It is good to be careful about food safety but sometime it gets into false phobia area. IMO. .

Let just assume for a moment that there is a trace of lead in the glaze.

-- First what are the possibility that it might leach into the soil ? That is it has to penetrat through the ceramic wall of about 3/8" thickness.
-- Assuming that it does, is it going to be water soluble , so the roots will take it up?
-- Assuming that it is water soluble and it will be taken by the roots, will it end up in the edible part of the plant ? at what quantity that be be considered a health hazard ?


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RE: Sealing ceramic pot for edible fruit?

Just as an update--I did some reading about lead and cadmium contamination in soils and in both cases fruit is the way to go. Lead exposure from contaminated soil is usually via inhalation of dust or ingestion of soil particles. It isn't readily taken up by plants and when it does it tends to be in the roots and leaves but not in the fruit. Cadmium is taken up more easily than lead; however it is also mainly in the roots and leaves but not in the fruit. Of course there could be other stuff in the glaze, but at least for these the lemon is probably safe.

Here are a couple links:

Cadmium (old paper)
Lead (handout from UCD)


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RE: Sealing ceramic pot for edible fruit?

Thank you for all the postings everybody, and the extra research sf_rhino. As I mentioned earlier, I have already applied two coatings of acrylic to the inside, mostly to prevent water from soaking into the ceramic, but it will act as a barrier. I liked the idea of using liner pots which I already did with one plant a few years ago. It does make it easier to move around and more flexible in changing planter-plant combinations from indoor to outdoor seasons. However, the planters and the pots are very different shapes, in particular the base diameter. These plants will need decent size containers and I would lose too much volume with liner pots, or I'd have to buy much larger planters for modest size pots. As a compromise I re-lined one of the planters with a plastic bag (+ the acrylic seal), then trimmed the bag down to soil level so it is almost invisible (and will be when I get something decorative to cover the soil). This will add more barrier but also make it easier to transplant at some stage.


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RE: Sealing ceramic pot for edible fruit?

Hi
I use this to seal my papercrete pots:

Here is a link that might be useful: liquid glass


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RE: Sealing ceramic pot for edible fruit?

Unless you're going to subsist on only the kumquats and lemons you grow in these containers, I wouldn't be concerned.


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