Clay Pot Irrigation - a simple adaptation of an ancient technique

Maddy Harland
Friday, 24th May 2013

Want to conserve water but still want to make sure you aren't under-watering your garden? Want to establish a simple greenhouse irrigation system? Clay pot irrigation can save 50-70% of water without depriving your plants.

This is an adaptation of an ancient method of irrigation that is thought to have originated in Africa 4,000 years ago. It uses the porous nature of clay pots to allow osmotic pressure to suck the water into the soil where it is needed. People use beautiful fired pots called Olla with a narrow neck buried in the soil.

Unless you can make them yourself, this may prove an expensive solution so here's an inexpensive and simple alternative.

Get hold of an ordinary 25 cm (10 inch) terracotta pot. Plug the hole with a wine cork. Bury it almost up to its neck in the soil but not too deep so that soil falls into the pot. Fill it with water. Add a terracotta lid.

Plant seedlings or sow seeds 18 inches around the base of the pot. Water will slowly seep out through the clay wall of the pot, directly irrigating the soil around the pot. As the roots grow they will wrap themselves around the pot. The plants takes up almost all the water, and because the water source is now in the ground, evaporation is almost nil.

Keep the pot filled up and you will provide a steady source of irrigation when your plants need it.

I am trying this in my greenhouse between tomato, chilli, basil, thyme, parsley and tarragon plants this summer and see how often I need to replenish the pots and how much I can reduce watering as well.

Two pots left with orange cover & right uncovered

Maddy Harland is editor and co-founder of Permaculture, a magazine that covers all aspects of low impact, intelligent living, from permaculture gardening and regenerative agriculture to green building, technology, transport and community action. For more great ideas please SUBSCRIBE. Every print and digital subscriber get access to ALL our back issues since 1992 totally free of charge. 

More resources

Polyculture: higher yields; less water

Energy Cycling - An Original Permaculture Design Principle

Watch: Patrick Whitefield on the art of watering seedlings and slug prevention

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Deborah |
May 24, 2013 - 4:40pm

Terracotta wine coolers are excellent as cheaper substitutes as well. They are usually found in my area at second stores for 3 dollars or less.

Maddy Harland |
May 24, 2013 - 4:43pm

Great idea! I'll try that too.

Kathleen Weston |
May 24, 2013 - 8:04pm

A friend just emailed me the article on clay pot irrigation. I'm very interested in seeing more. Thank you

William M Scott |
May 24, 2013 - 10:59pm

Most of the terra cotta I see is glazed. Would that work?

Maddy Harland |
May 25, 2013 - 12:32pm

Hi, It needs to be unglazed to be porous.

Peter Adeline |
June 1, 2013 - 8:20am

Hi Maddy,
I'm a local potter, and I'd be interested in making some of these. If you could email me a sketch, photo, dimensions, etc, I'll make some and make you a present of a few. This isn't really a commercial proposition, as I can't compete on price with cheap terracotta imports, and in any case postage of larger ceramics is a nightmare (cost and fragility). Anyway, as a long-time supporter of what you are doing, I'd be happy to just give you some.
Peter

Maddy Harland |
June 10, 2013 - 9:28am

Dear Peter,

That is a really generous offer. At the moment I am using unglazed flower pots - 20 cm and 24 cm wide at the top. An olla can be large - the larger the pot the larger the area it will irrigate - but anything up to 25-30cm tall and 20 cm wide at its widest girth would be very useful. It would be good to experiment as I am finding even unglazed pots do not release the water fast enough. Many thanks,
Maddy

Maddy Harland |
June 10, 2013 - 9:37am
Alasdair |
June 29, 2014 - 2:12pm

I imagine this would help deter slugs too because the surface of the earth around would be dry. They might collect around the pots though.
I notice that since I switched to watering my greenhouses in the morning so that the top of the soil isn't so wet at night, I have much less slug damage.

jmquet |
February 11, 2015 - 8:18am

check this great website for irrigation related guides ...
h2oirrigation.ae
please do check it out....

Stephanie Boucher |
May 16, 2016 - 12:39pm

What was the result of this experiment, Maddy? I'm trying it in my polytunnel now and I'm curious to know whether you thought it worked well enough to continue using clay pots.

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