Thursday, April 21, 2016

Ole? Olla!! Low-Tech, Efficient Irrigation Method

Posted by: Deryn Davidson, Horticulture Agent, Boulder County

In Colorado, water has been in the news a lot recently (and the CO-Horts blog). Most notably, we have the new bill that was passed and is soon to be signed into law, which will legalize rain water harvesting on residential properties (for more information see the previous blog post). So now we all have to figure out how we are going to use this captured rain water. Well, one option I’d like to introduce is the OLLA!! Maybe some of you are familiar with this ancient, low-tech, low-cost, high-efficiency irrigation method, but it was new to me.
I first learned about this ancient irrigation technique in the book “Gardening with Less Water” by David A. Bainbridge. Bainbridge writes that he discovered the olla when reading excerpts from, what he called, “a 2,000  year old Chinese agriculture extension book”. He is referring to the “Book of Fan Shengzhi” which is a collective of agricultural masterpieces written at the end of the Han Dynasty (206BC-8AD) by an important agronomist and scientist of the time, Fan Shengzhi. It was written at the request of the Emperor with the intention of helping farmers who had limited resources learn the best techniques for farming in the Yellow River drainage area. The olla, by its Spanish name, has been used by many, many cultures for cooking, storage, cooling and irrigation.
Okay, so what is this thing?? The olla is a clay pot that, for irrigation purposes, you bury and fill with water which then slowly seeps out. Simple. According to many, it is one of the most efficient irrigation methods around. Because the pot is below ground and has a narrow neck that just barely extends out of the ground, very little water is lost to evaporation or runoff. The water distribution is regulated by the water needs of the plant you’ve buried it next to. As the soil dries the water seeps out of the micro-pores of the clay. When the water demands have been met and the soil is moist, the water seepage stops. This technique can be used on a small scale in a flower pot, medium scale in your veggie garden and even large scale agriculture and landscape restoration projects.

Ollas can be purchased or homemade. To make your own (caveat: I’ve never done this but, plan on trying it) you take 2 terra cotta pots of the same size, seal the bottom of one so that water won’t flow out when it's filled with water, invert the other pot and glue the rims of the two pots together (you can use silicon or any other water proof adhesive). DONE! Now you dig your hole and bury your olla leaving about an inch above ground. Fill with water and find a nice stone to cover the hole for even less evaporation.

Everyone’s soil is little different and different plants will require varying amounts of water so there’s no one size fits all, but you can experiment with how close to place your olla to plants and how often you need to refill it.
Have any of you used this ancient, low-tech, low-cost, high-efficiency irrigation method?? If so, I’d love to hear about your experience!! Ole!


  1. I can't wait to hear from folks who have tried this. One question: Must these be removed from the ground for winter? Terra cotta tends not to hold up to freezes.

  2. Let's all "holla" for ollas! I love how this looks and it is so simple!

  3. Hi, Deryn here...Excellent point about removing them in the winter.!You should remove them, clean them up and store them until the following spring.

  4. A less gorgeous but sort of similar technique: a 2 liter soda bottle, with a TINY needle hole poked in the bottom, and buried alongside your tomato plant (or whatever) up to the shoulder. Should be "planted" when you put in your plant. The tiny needle hole will slowly release water deeply, down at the roots. Refill through the top of the soda bottle as it dries out. Maybe I'll add a rock to the top of mine this year. As the plant grows the bottle is hidden by the leaves - but these ollas are much prettier!