How to use Ollas (sub-irrigating clay pots) to save water

I just put in a set of Ollas at one end of a vegetable bed to help keep my fall greens watered through our hottest, driest months here in Northern CA.  Searching the forums, I didn't see anything about Ollas, so I thought I'd start a new thread!

I'm attaching some pictures so you can see how I laid out the bed, buried the ollas and filled them with water.  (This is my first post with pictures - am I doing it right??)

Ollas work because they're made from porous terracotta and seep water gently into the root area underground, losing very little to evaporation.

I make the ones in the pictures.  You can see the ollas here on my website.

There are also tons of tutorials for making low cost DIY ollas from cheap terracotta flowerpots and caulk.  It doesn't have to be expensive!  (Also - if you buy 6 or more from me you automatically get 25% off, 12 or more and you get wholesale pricing - contact me through the website to inquire about a quote!)

Have you tried ollas?  What plants do you find work best with them?

Once I posted the thread, I found links to related topics!  (Of course.)

Here is the existing thread on Ollas, last updated about 7 years ago.

And here is another one, with pictures of the DIY, 2 flower pot method.

Although you found some other threads, thought i'd pop in with one thing about the terra cotta pot ollas, which was basically that you have to REALLY do research to get that one to work.

At least in the USA, there are a lot of 'terra cotta' pots that aren't actually fully terra cotta. They are terra cotta with a cement inner core, and that core ends up preventing the water from getting through, basically. I've had more than one business that I asked about their terra cotta pots, they assured me up and down were 'real' terra cotta. I tried them, didn't really see much benefit and ended up digging them up, and then a big windstorm came by and blew them over, shattering them, and they all had cement in the middle of the terra cotta. :-/

I know there are real terra cotta pots out there, but a lot of places don't really mean much by the term except that the outside is terra cotta, best I can tell.

Word has it that the really good ones are made from clay containing sawdust, rice hulls, or some other lightweight fine biomass that burns away on firing and leaves voids that the water can seep through. A friend of ours is taking pottery classes and she plans to do some experimenting to find what sort of mix works best.

shauna carr wrote:They are terra cotta with a cement inner core, and that core ends up preventing the water from getting through, basically. I've had more than one business that I asked about their terra cotta pots, they assured me up and down were 'real' terra cotta. I tried them, didn't really see much benefit and ended up digging them up, and then a big windstorm came by and blew them over, shattering them, and they all had cement in the middle of the terra cotta. :-/

This makes me so mad! As a potter and someone who makes real honest-to-goodness terracotta pots, it honestly never occurred to me that someone would do something like that!  Yikes.  

What *is* common, even with real terracotta, is that barium carbonate is mixed into the clay to help the surface finish look smoother. (True terracotta can get milky streaks on the surface.) When we were developing our clay recipe, I took that poison right out.  And now we get streaks occasionally, but I know there's no poison in the clay or in my studio.

Phil Stevens wrote:Word has it that the really good ones are made from clay containing sawdust, rice hulls, or some other lightweight fine biomass that burns away on firing and leaves voids that the water can seep through. A friend of ours is taking pottery classes and she plans to do some experimenting to find what sort of mix works best.

In properly fired clay, the clay itself should be plenty porous.  But if you're firing hot, and the clay vitrifies, you would need some other type of void.  

I'd worry that porous clay with extra voids would be too leaky and empty too fast!  But like all things pottery and gardening, there are a million variables.  Perhaps certain soils do better with extra leaky pots?

This may help your friend as a starting place: In my experience, RedArt terracotta (a common clay body in the US) fired to cone 04 is just right for the combination of porosity and strength.  Once you get to cone 5, it's completely vitrified and non-porous.  Vitrification starts around cone 02, so that might be a good place to start with a semi-porous body with extra voids.

I have this pot that I acquired somewhere, not sure if it is decorative or meant to be used.  It isn't terracotta, but it is porous.  Maybe I should play with it.

Hey all!  I'm adding an update to my post above.

Last week we had one of the hottest weeks ever here in California.  It was HOT!  We went to the mountains overnight to escape the worst of the heat and I expected to find totally dead lettuce when we returned.  But the lettuces I had planted around the new ollas (pictured above in the first post) were totally fine, perky even!

It also helps that these are heat tolerant varieties, Australian yellow (https://ortakitchengarden.com/products/australian-yellow-lettuce-seeds) and Brown goldring (https://www.wildgardenseed.com/product_info.php?products_id=84).

Here are pictures of my lettuce (watered by ollas) after 2 really, really hot days:

Anne Fletcher wrote:Hey all!  I'm adding an update to my post above.

Last week we had one of the hottest weeks ever here in California.  It was HOT!  We went to the mountains overnight to escape the worst of the heat and I expected to find totally dead lettuce when we returned.  But the lettuces I had planted around the new ollas (pictured above in the first post) were totally fine, perky even!

It also helps that these are heat tolerant varieties, Australian yellow (https://ortakitchengarden.com/products/australian-yellow-lettuce-seeds) and Brown goldring (https://www.wildgardenseed.com/product_info.php?products_id=84).

Here are pictures of my lettuce (watered by ollas) after 2 really, really hot days:

Aaaahhhhh, thank you for this info about your lettuce. I figured I just couldn’t grow lettuces during the summer in New Mexico but this gives me hope. I’m totally ordering those lettuce seeds!