[Arid_gardener] sealing clay pots
cczaplicki at cox.net
Wed Dec 1 16:16:52 MST 2004
> Hi all,
> I do a huge amount of container gardening, and teach container gardeneing, and
> here are some of my observations.
> When one gets down to what is in any of the sealers, it comes down to plastic.
> And, we all know how plastic deteriorates in our very sunny and warm climate
> (except the last 2 nights!).
> Mexican or other ethnic terra cotta does melt away with watering as it is not
> fired at very high temperatures after being made. (Though if the container
> lasts 5-10 years, that¹s a pretty good bang for the buck!). Italian, some
> European, some American and some of the Southeast Asian pottery is fired at
> much higher temperatures and stays integral for much longer. These pots give
> off a decidedly metallic ring when tapped with a hard object (if they do not
> have a crack!). The other pots are very much like tapping a brick. Not much
> ring or sound.
> For purposes of adequate drainage, I elevate all my terra cotta pots off the
> ground, leaving the hole free to drain. Yes, you do want to see some drainage,
> that is one way to tell if the soil in the pot is being watered properly.
> Elevate on metal pot stands, terra cotta stands, ³pot feet², small clay
> sauces, plastic ³deck protectors², leaving the hole free to drain. I do not
> use wood because of insects; brick is ok if it does not cover the hole in the
> pot. The containers do last longer with air moving around the pot. I do not
> use saucers, either, unless the pot is elevated up off the saucer in the above
> ways (or even using large sized crushed granite).
> Most of the gardening year in the low desert, the evaporation of water out
> through the sides of the pot cools the soil around the roots, helping make
> excellent drainage, and thus helps add oxygen to the soil (when water moves
> out, air rushes in behind it.) We need that air for the roots so they don¹t
> get root rot and for vigorous roots (unless you have a bog plant).
> When I made a fountain out of a terra cotta pot, I used the pottery sealer, 3
> coats, on the inside and outside. I repeated that application every six
> months. The fountain, when I left it behind in a previous home, was staying
> together after 3 years.
> One of the uses of pottery sealer is not for the southwest, but for the areas
> of the country and world where it freezes. Water soaks into the walls of a
> terra cotta container. Temps go to freezing. Water freezes, and all you
> scientists know that ice takes up more space than water. Thus, the pot cracks
> from the pressure of the ice. So, sealing pots in those climates makes sense.
> One can bring all pots indoors before chance of frost etc, but that timing
> varies much in those climates. And, with so little sun, UV radiation has much
> less chance of deteriorating the sealer.
> Make some sense? In summary, I use repeat coats of sealer if I¹m making a
> fountain. I do not use it otherwise, as I want the pots to ³breathe². Cooler
> pots are better for plants most of the year in the low desert. If sealer or
> tar is on a Mexican pot, for instance, it will break down pretty fast anyway,
> not to worry.
> Sorry for such a long reply! Get back with me if you have any comments or
> other questions!
> Cherie Czaplicki
> Master Gardener
> -----Original Message-----
> From: arid_gardener-bounces at CALS.arizona.edu
> [mailto:arid_gardener-bounces at CALS.arizona.edu]On Behalf Of Jacqueline
> Sent: Sunday, November 21, 2004 9:11 PM
> To: michele wronski
> Cc: arid_gardener at CALS.arizona.edu
> Subject: Re: [Arid_gardener] sealing clay pots
> In my experience, clay pots deteriorate when they come into direct
> contact with the ground. Watering the plant in the pot results in
> water attempting to exit the pot at the bottom. If there is a hole,
> the moisture goes through the hole into the ground and the bottom of
> the pot stays moist. Over time the bottom of the pot and the sides
> will crumble - this is worse for pots with holes in the bottom and also
> for pots with textured designs. Not sure why - perhaps they use a
> different type of clay for them than they do for the standard terra
> cotta pots.
> If the pot is raised off the ground (for example on bricks), the
> deterioration is not as big a problem because there is not the moisture
> buildup at the base of the pot. The sealer, in my opinion, makes the
> pot more water conserving (because the terra cotta does not absorb and
> release the moisture), but would not necessarily make it last longer.
> That said, anything that prevents the bottom of the pot from getting
> wet and staying wet would probably make the pot last longer if it is in
> contact with the earth. So to cover your bases if you cannot raise the
> pot, you could put the sealer on the outside of the bottom of the pot,
> as well as on the inside on the bottom and on the sides of the hole on
> the bottom to achieve maximum protection.
> Jackie Rich
> Master Gardener
> U of AZ Cooperative Extension Service
> On Friday, November 19, 2004, at 12:50 PM, michele wronski wrote:
>> > Dear Arid Gardener,
>> > There were some questions about selaing clay pots
>> > a few weeks ago. Some people suggested coating the
>> > pots with Thompson's seal or masonry seal before
>> > painting them a color.
>> > When I called Home Depot about these products
>> > they told me not to use them on clay pots.
>> > Instead I should use a terra cotta pot sealer which
>> > is much more effective at sealing the pots. They
>> > basically told me that Thompson's seal doesn't work at
>> > all.
>> > If I buy terra cotta pot sealer, will this be
>> > worth the money I spend in prolonging the life of the
>> > pot?
>> > Does the pot actually keep from cracking because I
>> > have sealed it? Thanks for the update. Sincerely,
>> > Michele
>> > micheledesigns at yahoo.com
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