What is an olla?

Slow release watering around growing plants

How to make inexpensive ollas using terracotta pots. A clever way to keep plants watered in both the greenhouse and outdoors. Full video at the end

Using an Olla is a great way to keep plants watered, especially in dry regions and in the height of summer. The way they work is by slowly releasing water directly to plant roots under the ground. This saves a lot of water since very little of it is lost to evaporation on the soil’s surface. Being slow-release it also means that you water your plants less.

Although you can purchase purpose-built Ollas, making your own using terracotta pots is both easy and inexpensive. In the video and instructions below I show two ways that you can convert ordinary plant pots into low-tech watering solutions for your own garden.

Materials Needed for this Project

The first way is very easy but much more of a hack than the second. The more permanent solution involves sealing the bottom of your pots with concrete. For this project you’ll need:

  • Terracotta Pots
  • Saucers to act as Lids. Use plastic ones if you want to reduce water loss.
  • Mounting Putty (also called BlueTak)
  • Cement & sand to make concrete — or just get this pre-mixed bag

An Ancient Way to keep Plants Watered

I don’t think anyone really knows how long ollas have been used to water plants. Being made from simple unglazed pots, they could have been around since the invention of pottery. Known more commonly throughout the American south-west, ollas are used to keep plants alive in arid climates. They’re useful in any growing climate though, especially in the hotter months.

The way they work is simple. Terracotta is porous and when a pot is filled with water, the moisture wicks through the terracotta. If you leave the pot in the open air you can see moisture beading up on the surface of the pot. It does the same thing when buried, keeping the soil around the pot moist and perfect for growing plants.

The Easy DIY Olla

If you buy ollas ready made for the garden, they can be beautiful items but also very pricey. Always on the look out for a low-cost solution, I’ve thought up two different ways to create my own using ordinary terracotta plant pots and saucers.

The first way is by plugging up the hole at the bottom of the pot with BlueTak — I used a generic white mounting putty as you can see in the photo below. There’s a piece stuck to the pot from the inside, and another from the outside. If I wanted to, I could remove the putty and reuse this pot as a planter in the future. This type of putty is non-toxic and safe around edible plants.

It’s also been suggested over on my YouTube channel to use a cork in the hole.

Putty seals the hole at the bottom

A More Permanent DIY Olla

The second way to make your own olla is to fill the bottom of your pot with about an inch of concrete. You make concrete by mixing one part of cement with two parts sand, and just enough water to get it moist but not sloppy. For a single olla you need about 1/2″ cup of cement and 1 cup of sand.

Pour the concrete into the pot, making sure to plug up the hole with a bit of putty first, and let it harden for 24 hours. If you wet the terracotta pot beforehand, it can create a better seal. I also opted to put a piece of paper underneath while my pot dried, just in case some of it leaked out.

Concrete seals the bottom in this more permanent solution

How to use Ollas

When your ollas are complete, bury them into the ground where your plants will be growing. Put them in all the way up to the rim and then fill the pots with water. Put the saucer on top as a lid and then refill with water when needed.

My ollas are in the greenhouse and they leak out about an inch of water per day. You can tell that they’re working if the soil around them looks more moist than the surrounding soil. Eventually, plant roots will find the source of the water and will grow around and into the exterior of the pots.

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Clayola Egypt’s low-tech watering setup can keep your houseplants or garden watered when you’re away.

The use of unglazed terracotta pots, also known as ollas, for efficient ‘drip’ irrigation in gardens goes back thousands of years, and is a proven low-tech method of conserving water while delivering moisture directly into the soil. And although it’s easy enough to build your own olla watering system with clay plant pots, sometimes you want a ready-made option, and one with some additional functionality, which is what Clayola Egypt has developed and is selling through Etsy.

The Clayola self-watering system, which comes in a set of 6 clay pots that are unglazed on the bottom to let water seep through, yet have a glazed top to minimize evaporation, is designed to be connected to a water reservoir in series, which then keeps the pots full of water for up to a month at a time. This makes the Clayola system a great option for a hands-off house and garden plant irrigation setup that could help make weekend trips or vacation time a bit easier, as it can keep plants watered automatically, with no expensive sensors or hardware required.

“As water evaporates from a plant’s leaves, it draws water from the soil and as the soil dries up water is drawn from the Clayola to the soil. In Effect the plant extracts the water it needs from each clay pot. After a while a plant’s root system will find the source of water and literally hug the Clayola, allowing for maximum water use.” – Clayola

Each of the Clayola pots, which measure 12 cm tall by 8 cm wide, has a lid that incorporates two connectors (one input and one outflow) that join the pot to the water supply and to the next pot in line, and a simple gravity siphon system inserted into the water reservoir (such as a 5-gallon water carboy) keeps the water level in each pot topped off automatically. According to the company, a 20-liter container of water can keep 6 to 8 plants watered for several weeks in the summer, and more than a month in the winter. It’s also recommended to connect a reclaimed water source, such as harvested rainwater or air conditioner condensation, to the water tank as a way to further conserve water.

The pots are handmade in Egypt, and can be shipped worldwide, with a set of 6 pots priced at about $30 plus shipping. More information can be found on the company’s Facebook page.

H/T Springwise

I’m the first to admit, I’m a massive bit of a nerd. I love my technology.

But sometimes, low-tech solutions deliver the most elegant, beautiful solution to a problem.

One of the biggest problems in my garden is water.

Summers are brutal here in Perth. Water is scarce, so we have water restrictions.

I can’t afford the $5000 or so for a bore, or equivalent for a greywater system right now. Retrofitting water tanks to this house would also be $$$, I collect as much of the rainfall as I can, but it’s gone all too soon.

Even the most sophisticated, drip reticulation system can only be switched on twice or thrice a week. And if we get a total sprinkler ban (it happens), then reticulation becomes completely redundant and we are only allowed to water by hand using a hose or watering can.

An ancient water-wise solution.

Luckily for me, farmers have been facing very low rainfall, average soils and warm climates for millennia. And a few years ago, I found Urban Homestead. The Durvaes family have been using ollas in their raised beds in their Pasadena, California garden for many years, with great success. Their plants thrive and their water use is minimal. It was the first time I had ever encountered ollas and I was immediately smitten. Ollas are an ancient form of irrigation, used for over 4000 years.

Traditionally, ollas are rounded terracotta vessels with a narrow neck. They are submerged into the soil, with just the neck protruding. Once filled with water, the olla seeps water into the surrounding soil, directly to the roots, right where it is needed. Obviously, no water is lost to runoff or evaporation.

Ollas are easy to move!

You can use ollas in large pots and the garden bed. I rotate my beds around, so the ollas can be moved easily enough too.

Plus, ollas are perfect if you are renting. You can dig them up and take them with you.

Great idea right?

Indeed yes!

But, Ollas are EXPENSIVE.

Getting traditional ollas shipped from the US equated to about $100 an olla!

Ouch!

For a while, I couldn’t find them in Australia. But a quick Google search for “ollas + Australia” will produce a few results for suppliers in Australia.

Again, ouch! While much cheaper than the US sites, Aussie-ollas are still pricy. I wouldn’t get much change from $200.00 to get a dozen ollas delivered to my door.

A DIY Economical Olla

Fortunately, a much simpler solution showed up in my Pinterest feed. It’s one of those things that when you look at it, you feel instantly silly for not thinking of it yourself sooner.

Homemade ollas using terracotta pots!

When I finally had the time to make them, I found the perfect pot size, on sale for just $1.00 each. Woohoo!

So for the much more budget-friendly price of $24.00 I made myself a dozen ollas. That’s $2.00 each!

Here’s how I made my ollas…

How to Make Awesome Two-Dollar Ollas

You will need

  • Two equal sized unglazed terracotta pots.
  • One tube of weatherproof silicone sealer*.
  • Optional: old pieces of pipe or hose to fit the drainage hole of the pot.

*I made twelve large ollas and three smallish ones. One tube of silicone sealer was enough to do the lot, with some to spare. I also used a food-safe grade silicone, the kind used for water tanks and indoor plumbing.

Process

  1. I set up a production line on a tarpaulin.

2. I sealed the drainage hole in the bottom of the pots with silicone, both inside and out, to make doubly sure it won’t drain when filled with water. I cut pieces of milk bottle plastic to stick on the inside of the pot to act as a plug.

3. I planned to add a hose neck to refill the olla. But my old bit of garden house was too wide, I couldn’t manage to secure it properly to the top of the pot. Instead, I submerged the olla them with the top at soil level. A pot saucer acts a lid to prevent evaporation and debris from falling in the olla

4. When both halves were dry, I placed one on top of the other (see below). I piped the silicone around the rim of the bottom pot, placed the top one on top and smoothed the silicone around the seam using a plastic spatula. Some pots needed extra silicone around the rim to get a good, thick seal.

5. Leave for 24 hours for the silicone to cure and dry completely.

6. Once they have dried, I filled them with water for a test run to ensure there were no leaks. They held their water! My large ollas hold a generous 3-litre drink.

I made a dozen ollas for less than $30!

I’m thrilled with how they turned out. I’ll be making more this week in preparation for a hot summer ahead.

In part two of this post, I show you how to use ollas in your garden beds. Go check it out! you won’t believe the “before” and “after” results!

Have you visited the Subscriber Resource Library yet?

A summer heatwave can reduce even a well-established garden to dust in a matter of days. Be sure to sign up for A Farm of Your Home’s Subscriber Resource Library access and download my free Heatwave Checklist! I share how you can beat the heat and protect your plants, and what not to do when the heat is on!

Do you use ollas? Do you think you might give them a go? If you have any questions, please do not hesitate to leave me a comment below.

How to use an olla to water your garden

We’ve been talking about ollas for the last few months in our efforts to find more efficient methods or watering. If you’re just joining us now, an olla is essentially an unglazed clay pot that you bury in the ground, fill with water, and allow plant roots to pull as much water as they need through the clay.

Photo courtesy of Dripping Springs Ollas

We put an olla to test in the Sunset Test Garden and have been pretty impressed with the results so far. All we need to do is fill the olla with water once a week and the plants take care of themselves.

Here’s how we set it up.

Senior garden editor, Johanna Silver, getting her hands dirty but keeping those sneakers clean.

Step 1: Dig

Dig a hole in a well amended garden bed large enough to submerge the olla.

Step 2: Bury

Bury the olla in the ground, leaving the neck exposed above soil level.

Step 3: Plant

Lay out plants within a 36″ diameter to the olla. We chose Mediterranean herbs, including German thyme, variegated thyme, tricolor sage, and ‘Magic Mountain’ basil.

Step 4: Water

Fill the olla to the brim with water and cover with the clay cap to prevent evaporation. Plant roots will draw water through the clay.

UPDATE (2 months later): For the first few weeks after planting out the herb seedlings, I also hand-watered the plants with a watering can, assuming that baby plant roots might not have enough pull to draw water from up to 36 inches away. Once the plants got established, I’ve relied entirely on the olla to water and the herbs are thriving.

In fact, the ‘Magic Mountain’ basil grew so quickly that it began taking over the rest of the bed and I ended up replacing it with low-growing ‘Chef’s Choice’ rosemary. Stay tuned for an aftershot of the herb bed in an upcoming garden-to-table story!

Clay Pot Irrigation – a simple adaptation of an ancient technique

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.

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

Since it is summertime, I thought I would share this great summer project from the Pottery Making Illustrated archives! In this project, Sumi von Dassow demonstrates how to make an olla watering system out of clay. What’s an olla watering system, you wonder? It is an unglazed porous bottle form that is buried in the garden amongst your plants. When it is filled with water, it slowly releases the water into the soil to be drawn up by your plants roots when they need it. Read on to find out how to make your very own! – Jennifer Poellot Harnetty, editor.

PS. Get tips for using your olla watering system in the July/August 2018 issue of Pottery Making Illustrated!

As pottery and cooking go hand-in-hand, so too do cooking and gardening. Potters know the pleasure of cooking and serving from hand-made dishes designed especially for homemade recipes; and every cook knows the sweetest peas and corn are those that are harvested fresh from the garden moments before they are to be eaten. To complete the triangle and bring pottery into the garden, you can make ollas to keep your thirstiest vegetable plants healthy and productive through the hottest summer weather.

How to Make Pottery

Get expert guidance on the fundamentals when you , How to Make Pottery.

An olla (pronounced oya) is an unglazed bottle made from porous clay. Filled with water and buried next to a garden plant, the olla allows water to seep slowly into the soil to be drawn up by the roots as needed. Tomatoes growing with an olla suffer less from cultural problems such as blossom-end-rot as they receive a steady supply of water. Cucumbers are less likely to grow bitter in hot weather. Pumpkins and squash can grow big and plump without splitting their skins. Ollas keep the soil from drying out but never contribute to overwatering—if the soil is moist enough, water doesn’t seep out of the porous clay. As long as you keep the olla full, the plants always have exactly as much water as they want.

For most purposes, a fairly large olla is desirable so you don’t have to fill it too often. You want a nice round bottle with a long, narrow neck so you can bury it fairly deep and leave the neck sticking out of the ground for easy filling. You can throw a bottle from 6 or so pounds of clay, trimming the excess from the foot as needed. Or, you can make a bigger bottle with less clay if you throw it in two sections.

1 Throw a wide, sturdy bowl. Cut the rim at a downward angle toward the inside, and measure with calipers.

2 Throw a second bowl to the same rim diameter. Open it up all the way to the bat. Trim the angle of the rim upward.

Two-Section Bottle

Start with 3 or 4 pounds of clay and throw a sturdy bowl on a bat. This will be the bottom section of the bottle, so don’t make it too delicate. When you cut the rim, bevel it so it angles down toward the inside of the bowl, then measure the outside of the rim with calipers (1).

With an equal amount of clay, throw a second bowl (this will be the top section), but open it all the way down to the bat, making an opening big enough to get a few fingers inside and leaving a generous amount of clay at the base. Measure the rim with calipers to make sure it matches the rim diameter of the first bowl, and bevel it in the opposite direction. This means it needs to angle down toward the outside of the rim. With the two cuts angled in opposite directions, they will fit together perfectly and make a more secure joint than two flat cuts. Don’t wire under either piece.

Allow the base bowl to stiffen slightly, so it can support the weight of the second section. Put the bat with the bottom bowl back on the wheel and pick up the bat with the second section. Flip it upside down, holding it by the bat so it stays perfectly round, and set it on the first section rim to rim, matching them up exactly (2). Use your fingers and then a stiff rib to smooth the two pieces together. Cut the top section free from the bat by running your needle tool under the edge as far as it will go, then cut it the rest of the way with a wire. Remove the bat.

3 Join the two sections together. Then, widen the opening to fit your hand and join the inside seam.

4 Create a neck by alternately pulling and collaring. You want the neck to be at least 3 inches tall and 1½ inches in diameter.

There will be a thick collar of clay where the pot was stuck to the bat. Use this clay to form a tall, narrow neck. First you need to make the opening large enough to get your hand inside to smooth the area where you joined the two sections (3). Next, pull up the neck and collar it in until it’s about three inches tall and the opening is 1½ inches or so in diameter (4).

You shouldn’t have a lot of clay to trim from around the foot, but if you feel it’s heavier than it needs to be, trim it with a trimming knife (5) or turn it over in a chuck to trim. You don’t need a foot on the bottom—in fact the bottom doesn’t even need to be flat—but you shouldn’t leave it too heavy. Water will pass through it more quickly if it’s not too thick. Bisque fire the pot.

5 Trim what you can from the base and refine the form as needed. Bisque fire the pot.

6 Bury the olla up to its neck in the soil. Plant seedlings a few inches away from the neck of the olla.

Ollas are forms commonly made by the famous Mata Ortiz potters in Mexico. See this Mata Ortiz pottery project in the PMI archives!

**First published in 2018.

Gardening can be hard. Don’t believe anyone who tells you otherwise. But if you’re willing to get out there every day or so and weed and water, it’s not so bad. There are, however, days when you wake up late and the sun is burning and you’re rushing to get to work and you really need to take the time to water with a watering can (to avoid getting the tomato plant leaves wet, which will burn in the hot sun… You should have gotten out a few hours earlier so you could have watered more quickly with the hose). So your options are now: Are you going to be lazy and burn your tomatoes or are you going to be late for work? Neither is ideal. Generally work wins and I pray that my tomatoes will forgive me.

Sometimes I wait until I get back from work to water. Because some people in my community garden water after the heat of the day has broken. But watering later means you run the risk of having mildew grow on plant leaves, which leads to disease – and more sad tomato plants that are disappointed in me.

Then there are the dry patches in my garden, where even if I water in the morning, on a blazing hot day they’re bone dry by afternoon. I can’t use drip irrigation because I’m in a community garden. I have some mulch to stop water from evaporating, but it’s not incredibly effective. I’ve added more soil and compost with peat to retain water. And yet, thirsty tomatoes and herbs.

So I scoured the internet and the internet told me about clay pots called ollas. It’s a millenia-old idea, which appeals to me. If it ain’t broke, right? You bury sealed clay pots in the soil and fill them with water, which slowly leaches out as needed throughout the clay.

I’m so far from a DIY-type person that it’s laughable. I need supervision to use a hand drill. I have a friend that I take far too much advantage of when my dishwasher breaks/wall needs holes covered/cabinets need to be removed, toilets start dripping. I pay him in food, wine, jam and desserts. Everyone needs a friend like him.

So when I read about olla pots and realized that the best way for me to make one involved gluing things, I got nervous. What the heck is Gorilla Glue? Is the silicone I have for sealing my sink the same as the instructions? Was I going to poison my tomatoes by burying it in soil? Apparently not. Both it and the glue are waterproof and shouldn’t leach. Still, just to be safe, I used the silicone inside the pot rather than to connect the two pots, to minimize contact with the soil. Anything that says you should avoid touching it and wash your hands immediately if you do sounds like a bad idea for a garden…

But I followed these instructions and now have olla pots buried in my garden. And it wasn’t super hard. Even for me. Because, as my mother would say, “Stupider people than you have done it.” She meant that in a really nice way.

I made a call-out to friends with basements and gardens (not young people who live in apartments and kill any and all potted plants given to them upon moving to said apartments) and got five pots from a woman who’s old enough to have grandchildren but strong enough to bike an hour and a half to and from the Atwater Market because use it or lose it (a woman after my own heart). My co-gardener bought the expensive glue and told me not to waste it. And I got out that silicone, which hadn’t dried up or expired or whatever silicone does (I doubt it expires; the whole idea is that it lasts). And I went to work.

HOW TO GLUE OLLA POTS

The idea behind ollas is that you glue two of them together at the thick rim parts so there’s a hole on the top and bottom. Before glueing, though, you seal the hole at the bottom of one while leaving the hole of the inverted clay pot on top open. That way you can keep filling the olla with water throughout the summer and not have the water just drain out the bottom of the lower pot.

The website where I got my instructions said you can use a tile to do this. I didn’t have any tiles, and I couldn’t use anything metal, which would rust in the soil. So finally I thought about a small glass jar, which I used silicone to glue to the bottom of the first pot.

I prayed it was properly sealed and then used a thin layer of Gorilla Glue (follow the instructions on the bottle) to glue the two pots together. I weighed them down with a thick baking sheet and let it set overnight.

In the morning, I could see that there were some parts that weren’t totally sealed, so I filled in the spots with more glue and let it set for another 24 hours. I don’t think my roommate loved having these weird pots topped with precariously balanced baking sheets sitting on our kitchen table for two days, but he didn’t say anything. Sign of a good roommate.

The last step was testing the seal. I held my breath as I poured water into the top, unsealed hole of my ollas. No leaks! Oh, hurray! I’m not a total mess-up. I went to my garden and dug two holes in the driest areas and buried the pots up to one-inch from their tops. You don’t want to bury them fully or soil will get into the hole. Even if you put a rock on top, like I did.

And now we wait to see if those areas of the garden do better. It’s a season-long experiment – one in which I have to avoid accidentally digging into or stepping on the ollas and breaking them. This will be my challenge. But at least I have more silicone and Gorilla Glue if I ever need it.

A how to guide to Olla pots – an effective traditional irrigation system.

Find out more about this traditional irrigation technique that uses Olla’s, or clay pots to effectively and efficiently deliver water to the plants that needs them. Remember if you live in rainy climate this is a useful method for polytunnles and greenhouse. IN your live in an arid climate this could be a need to know technique.

How Ollas work

The clay pot is buried in the ground, with its neck protruding out. There are many small holes doted around the pot due its particular firing method of construction. As it is filled up, it evenly distributes water to the surrounding soil. However the water does not simply empty as it is filled, it only flows out into dry soil. When the soil is sufficiently saturated, water is unable to flow out.

Eventually, the roots of plants will be drawn to the pot, feeding water directly to the plants. Compared to surface watering, this method is far more efficient as water is directly injected into the ground and is not subject to evaporation or run-off.

By keeping water away from the surface layer of soil, you also go a long way in preventing weed growth. You can also, as usual, surround the pots with mulch to further suppress weeds, making sure that all the water is directed to the plants that really need it.

In this video, Will Geusz takes you through the methods and techniques he has experimented with, taking a look at the science and construction of Olla pots. Take a look at Ollas in the wider context of responsible attitudes to water and also where to buy or how to make them.

More information

Maddy Harland attempts a modern interpretation of Olla pot irrigation in her greenhouse at home.

Patrick Whitefield on the art of watering seedlings and slug preventation

20 ways to control slugs in a permaculture garden or allotment

Clay pot irrigation – a simple adaptation of an ancient technique

Polyculture – higher yields, less water

I first encountered the concept of using unglazed clay vessels for sub-surface irrigation in Bill Mollison’s “The Global Gardener” film series. Mollison comments that the technique might be, to paraphrase, “the most efficient irrigation system in the world.” More recently I noted with interest that the fine folks at Path to Freedom were employing these clay pots for some of their raised beds, which led me to wonder about how I might experiment with them as a potential sub-surface irrigation system. Here’s what I found….

A Sri Lankan villager fills his olla
Photo copyright © Craig Mackintosh Ollas (pronounced “oy-yahs”) are unglazed clay/terra-cotta pots with a bottle or tapered shape that are buried in the ground with the top/neck exposed above the soil surface and filled with water for sub-surface irrigation of plants. This irrigation technology is an ancient method, thought to have originated in Northern Africa with evidence of use in China for over 4000 years and still practiced today in several countries, notably India, Iran, Brazil (Bulten, 2006; Power, 1985; Yadav, 1974; Anon, 1978 and 1983) and Burkina Faso (Laker, 2000; AE Daka, 2001).

Ollas may be the most efficient method of local plant irrigation in drylands known to humanity due to the microporous (unglazed) walls that do “not allow water to flow freely from the pot, but guides water seepage from it in the direction where suction develops. When buried neck deep into the ground, filled with water, and crops planted adjacent to it, the clay pot effects s

ub-surface irrigation as water oozes out of it due to the suction force which attracts water molecules to the plant roots. The suction force is created by soil moisture tension and/or plant roots themselves.” (AE Daka – 2001.) The plant roots grow around the pots and only “pull” moisture when needed, never wasting a single drop. “Ollas virtually eliminate the runoff and evaporation common in modern irrigation systems, allowing the plant to absorb nearly 100 percent of water.” (City of Austin Water Conservation, 2006.)

To use ollas in a garden or farm, one buries the olla in the soil leaving the top slightly protruding from the soil (ideally the neck of the olla is glazed to prevent evaporation or it should be reasonable to apply a surface mulch that covers the neck of the olla without spilling into the opening). The olla is filled with water and the opening is then capped (with a rock, clay plate or other available material to prevent mosquito breeding, soil intrusion and evaporation).

“Depending on factors such as the plant’s water needs, soil type, time of year, and environment ollas may need filling weekly or daily. Water usually takes between 24 and 72 hours to flow through an olla.” (Bulten, 2006) Water should be added to an olla whenever the water level in the olla falls below 50% in order to avoid build up of salt residues along surfaces of the olla that may prevent desired seepage.

Pottery production is an age-old skill and low-tech cottage industry
that should see a rebirth. Photo copyright © Craig Mackintosh

When assessed in the context of a movement towards local self reliance, the advantages of ollas seem to be astounding (the following list is provided by AE Daka’s research):

  1. Since clay pots are made by rural women they create employment and opportunities for small-scale home industries to manufacture them in rural areas. This will help generate rural income for household food security.
  2. They are affordable A 5 liter capacity clay pot costs US$0.25.
  3. Clay pot irrigation allows a farmer to raise seedlings in situ instead of transporting them from nurseries. Clay pots are installed directly where seedlings are to be planted and this allows a farmer to plant the seed next to the clay pot where it germinates and gets established.
  4. The system is suitable for vegetables as well as perennial horticultural orchard or plantation crops and woodlots .
  5. Water savings of 50-70 % are realized, particularly for vegetable crops. Loss of water due to deep percolation beyond the root zone is reduced if not avoided.
  6. Soil moisture is always available almost at field capacity giving the crop full security against water stress.
  7. The system inherently checks against over-irrigation.
  8. The much smaller quantities of water and less frequent watering required, reduce the amount of labour required for irrigation tremendously.
  9. Much less labour is required for weeding since weeds do not prosper, as the soil surface remains dry throughout the growing season.
  10. Domestic water effluent from kitchens can easily be recycled and used in clay pot irrigation in backyards. The water used for cleaning utensils in the kitchen can be used to refill the pots in a backyard garden. This saves on scarce water and reduces the need to use fresh water.
  11. It saves on the amount of fertilizer to be applied per unit area of land if the fertilizer is applied in clay pots and is later absorbed as solute via water movement to the plants.
  12. The soil of the seedbed under the clay pot system does not get sealed due to water impact but remains loose and well aerated.
  13. The clay pots can be installed on undulating ground.

Some of the disadvantages of ollas include the potential for winter breakage if left in the ground in areas with a winter freeze – “our research has shown damage to some Ollas (out of hundreds) when left buried in the ground over winter.” Bulten, 2006. Of course, for kitchen garden beds in temperate climates, digging up ollas at the onset of winter could be standard garden maintenance. Prolonged use is likely to decrease porosity, some heavy soils may be inappropriate to site ollas and the longevity of ollas (without frost) is unknown but estimated in one study as 5 years or more. Also, despite the purported efficiencies, and the long history of use and simple manufacturing requirements (more below), ollas are difficult to find locally, and may be, especially in the affluent, “over-regulated world,” prohibitively expensive to deploy. Finally, there seems to be somewhat conflicting and insufficient research as to the optimal shape, volume and materials for ollas.

Clay pots, like these in Sri Lanka, can also be used as water coolers
in dry climates. See A Refrigerator that Runs Without Electricity
to see how this works. Photo copyright © Craig Mackintosh The consensus from available research is that the optimal size and shape of the olla is dependent on the plants being irrigated. No research seems to be available on the consequences of using ollas in a dense polyculture. One “should match olla porosity, size and shape to plants’ water needs, root size and root distribution.” (City of Austin Water Conservation, 2006.) “As a general guide, smaller ollas are good for container gardening. The larger ollas are good for larger containers or outside ground applications.” (Bulten, 2006.) Intuitively, a more tapered, flat-bottomed vessel with a narrow neck (to reduce evaporation and contamination) should be more efficient due to an increased surface area and theoretically increased water spread, allowing for less ollas to be used to sufficiently irrigate a greater space. Capacities of 5 liters to 12 liters have been described with 10-12 liter volumes being used to irrigate vine crops (tomatoes, curcurbits, etc.). More empirical research would be beneficial to the world community.

Similarly, available research is not clear on the optimal spacing of plants around the ollas. Clearly spacing will be dependent on the shape and size of the ollas so this does not seem surprising. Based on available research the following tables can be created to describe potential spacing of ollas based on a rough estimate of water spread.

Additionally, John Bulten provides the following notes and diagram:

“Plant seeds or plants within 2” – 5” radius based on olla size.”

In another study, “clay pots with a capacity of 5 liters each and made by rural women were installed at 0.5 m intervals in the study plots by burying them neck deep in the prepared seed beds.” (AE Daka – 2001.)

There appears to be similar, but distinct approaches to making ollas, mostly defined by the local availability of materials and technology. I’ve included descriptions on making ollas verbatim with the intent of assembling a loose set of guidelines to inform local artisans to invent an appropriate approach for the San Francisco Bay Area (or wherever else olla manufacture is being attempted):

Ollas in Sri Lanka
Photo copyright © Craig Mackintosh

“Maria created her highly prized black pots by using the bottom of an old plate (puki)… Beginning by patting a tortilla shaped piece of clay in the puki, Maria then rolled a lump of clay between her palms, creating a long clay rope of uniform thickness. Pinching and pressing this coil onto a clay tortilla while turning her puki with her other hand, Maria formed the base of the olla. Successive layers of coils were added until the vessel was completed.” (Hoxie)

“To make the urns, the ministry created plaster of Paris molds from pumpkins, squash and gourds of various sizes. Workers pour liquid clay into the molds to shape the urns and then fire them in the kiln to solidify the clay. The urns retail for $12 to $15 depending on size.” (City of Austin Water Conservation, 2006)

“The clay pots are made from a mixture of clay and sand in the ratio of 4:1 and with an effective porosity ranging from 10-15%. The clay pots are made by rural women using their hands to mould them into different shapes, i.e. cylindrical/round with somewhat flat bottom. After they are made, glazing is not done so as to retain their natural porosity i.e. the walls remain micro-porous. The pots are then tempered by burning them in a pit fire from firewood at undetermined temperature. Small-scale earthen-ware manufacturers use kilns to temper such ceramic pots at 1200oC. This is done in order to eliminate the swelling and shrinking properties of clay, which would cause cracking of the pots. Women believe that the type of clay used to make the pots is very important and it requires an experienced old woman to identify clay that would not crack unduly during the tempering process and indeed when installed under field conditions.” (AE Daka – 2001)

“If suitable pots are not available, they can be easily made by hand or on a pottery wheel. Depending on the clay, sand, rice hulls, or sawdust may be added at a ratio of up to 1:4 to increase the porosity of the pots. Although closed-oven firing at temperatures exceeding 450 degrees Celsius is ideal, pots can be fired in open pits at temperatures of 200 to 300 degrees Celsius. Opening: narrow neck (reduce opening size to reduce evaporation and contamination) (Barak, 2006).
Composition: unglazed porous clay – you can either use a crude clay which has larger/mixed particulate sizes and is not quite pure which will result in larger pores during the firing process. Or you can mix 20% sand with 20% quality clays (the best option) or the same % of sifted rice hulls or sawdust. The firing process will of course burn out the filler leaving uniform pores and a high-quality pot. (Barak, 2006)

The pots I use are low-quality clay with a low firing temperature so they are prone to breakage and/or having pores that transmit water very rapidly. As best as I can tell they use course red clay with sand impurities and some straw mixed in (probably less than 20%) and are fired are probably 800 F which is what you normally achieve in open firing pits.” (Barak, 2006)

This video shows a potter’s wheel technique:

This video shows a different technique:

Some links and references:

Ollas: Unglazed Clay Pots Water Your Garden Easily

By Guest Author Mary Kathryn Dunston

No matter how much we know about gardening, there is always something new to learn. And sometimes the newest ideas hail from years gone by. What I’m talking about here is clay pot irrigation, a technique which originated thousands of years ago. We know this because clay pots, called ollas, have been found in archaeological digs around the world.

What is an olla and how does it work?

An olla is a low fired terra cotta clay pot that is buried neck deep in a garden, raised bed or container. It is then filled with water and plants are planted around the olla.

As the roots of the plants dry up the soil, a phenomenon called soil moisture tension is created. This causes the dry soil to literally draw the water through the walls of the porous clay pot. The most efficient ollas have a bulbous bottom and a neck that is wide enough to make filling and checking the water level easy. A lid of some kind is important because it keeps the water in the olla from evaporating and keeps out frogs, mosquitoes, and other unwanted visitors.

The benefit of ollas is that they save up to 70% in water use compared to topical watering, since they are buried up to 1 foot underground (the bulbous part). For folks on city water, that is a $ saver. The saving occurs because the water-filled olla is so deep it greatly decreases the evaporation rate. This also encourages plants around it to grow a large root base, since the roots get water as they need it.

Another plus is that this deep watering system does not feed surface seeds, so weed growth is greatly decreased. By how much? That depends on personal garden maintenance. I think of weeding like dusting a house. Some people don’t mind a little dust (or weeds), others like a super tidy house (or garden). But no matter how you like things, less surface water means less weeds can grow, and that’s a good thing! Having said that, many people plant starter plants around an olla, but if seeds are planted, it would be necessary to water your seeds until their root system can benefit from the clay pot irrigation. That usually takes several weeks, depending on the plant.

What is soil moisture tension?

We know that ollas work by soil moisture tension, but what is that exactly? The best example is to picture a dry paper towel touching a puddle of water. Without you doing anything, the dry paper towel will start absorbing the water, until the paper towel is saturated. In the case of the water-filled olla, the soil is the dry part, and it will pull the water out of the olla until the soil has all it needs – the soil won’t be saturated, but it’s sufficiently watered. And since the roots of a plant are steadily absorbing the water from the soil, the soil replenishes its water supply by continually pulling from the clay pot. That is perfect supply and demand. Your job is to check the olla every 3-7 days to see if it needs water. Now that’s simple!

You now know about filling the olla and having the dry soil pull the water through its porous walls. Yet, if your weather forecast is threatening rain, rain and more rain (which can split tomatoes and melons), don’t put water in the olla. From above, the empty olla is just a hole in the ground, and since water always runs downhill, gravity will refill that olla with excess rainwater.

How far does an olla water?

How far an olla waters depends on its size – the larger the olla, the further out it can water. Ollas range from 1 quart/liter to 2.9 gallons/11 liters and traditionally, smaller versions were for smaller plants, since the roots of small plants don’t grow very deep. But today, smaller ollas are often used in containers and the larger models are used in the ground, raised beds and large containers. The largest olla will water a 3 foot circle in many soil types. The watering radius decreases as the olla’s size decreases.

What plants can I water with an olla?

Any plant can be watered with an olla. Larger vegetables, such as tomatoes, need plenty of room to grow, so most people put 3 tomatoes and one companion plant (basil, for example) around one large 2.9 gallon/11 liter olla. Newly planted trees and shrubs can also benefit from ollas. 2.9 gallons of water will last for days next to a new tree, helping it get through that first year. After the first year, dig up the olla and relocate it.

A well made, thick-walled olla will withstand extreme temperatures and can be left in the ground through the winter (but make sure it’s free of water before the first frost). Some ollas are more delicate, so if you live in a cold region, take note of the limits of the olla you purchase.

Buy on Amazon: Dripping Springs Olla

Olla maintenance

Ollas are really easy to maintain. If you hand till your garden, you can bury your olla next to peppers or tomatoes, or tuck them into squash hills and call it a day. Thick walled versions are tough enough to withstand some sloppy shovel action, but a tiller bland is asking a bit much of terra cotta. If you machine till your garden, it would be wise to pull your ollas up every season, or carefully till around them.

If your water is heavy on minerals, as some wells are, every few years you may need to soak your ollas in a mild vinegar solution for a few hours and then scrub the outside. Then soak with clear water to rinse.

If you see debris in your olla, overfill it with water, and allow the debris to flush out or dig it up, turn it on its side and wash it out.

I have personally left my ollas in the ground (35 of them), filled them with well water and hand tilled around them for over 5 years, and they perform without trouble. I am in Zone 7a. I have heard many stories of olla users from Canada to Southern California, and Washington State to Florida, who have enjoyed the simple watering system of clay pot irrigation. They have discovered this ancient way of watering and benefited from this simplistic, organic system. If you have a busy life, want to ease up on watering time, or just enjoy making life simpler, try gardening with an olla. You won’t be disappointed. Happy Olla Gardening!

For more information, see:

Action sheet on buried clay pot irrigation from the Pan African Conservation Education Project.

This article on Ollas from PermacultureNews.org

This research study on buried clay pot irrigation

Mary Kathryn Dunston has helped develop the company Dripping Springs Ollas She has been gardening since the Hippie movement (she was very young), and gets great joy from teaching people a healthy, organic, water-wise way to grow food for themselves, and their neighbors! She can be reached at [email protected]

Buried Clay Pot Irrigation: Low Maintenance Solution

If you are looking for ways to reduce water usage this summer (and low maintenance watering), buried clay pot irrigation might just be the trick you’re after. It’s a new concept to me but this method has apparently been around for centuries yet still offers value to today’s gardener. Here’s a bunch of info to get you started and then I added several different DIY irrigation methods at the bottom (some simple and small enough for house plants while others are more suited for gardens and shrubbery). Enjoy!

Use Vessels That Are Unglazed For This Project

Here’s the scoop: The idea is to bury clay pots (Ollas) in the ground making sure to keep the mouth level with (or just above) the soil surface and then fill them with water.

As the soil dries, suction develops and the water slowly seeps out from inside the pot and into the soil around it (the suction force is created by soil moisture tension and/or plant roots themselves, source). This is a naturally automatic system, if it’s been raining, the soil is wet so there is no moisture tension and the pots don’t release any water. The soil gets just what it needs, right when it needs it with no gadgets or sensors required!

Arrange the pots in clusters and plant your garden around them. How many do you need? Each pot will water the plants within its immediate area (responding to the soil moisture tension around it). The larger the pot you use, the larger the area it covers (and the less often you have to top it up with water).

Since the pots are buried, water is delivered more efficiently at root level rather than above the soil surface (with water needing to travel a few inches down to reach the roots). To keep the system working optimally, add more water to the pots as needed and avoid letting them dry out completely. Dig the pots up at the end of the growing season to prevent breakage over cold winter months. This method can be used in container gardening as well, you’ll just need to use smaller clay pots that will fit inside the containers or planter boxes leaving enough room for the plants to thrive.

What kind of pots to use: They need to be unglazed clay pots (otherwise the water will be sealed inside and won’t seep out) and can have a wide or narrow mouth. Select pots that don’t have a long or fragile neck so they’ll withstand being buried without breaking. You can use regular flower pots but make sure to seal closed the drainage hole. Keep the mouth of the jar covered to prevent insects and debris from getting inside and to help reduce water loss through evaporation. If there are no fitted lids for the jars, you can use flat rocks, shells or ceramic tiles depending on the size of the hole.

A clay pot in operation when installed neck-deep into the ground and filled with water. Source: upetd.up.ac.za (pdf download)

Tip: To test whether a pot will work or not, fill it with water and watch if the surface becomes damp. If it does, it’s porous enough.

Bonus: Because the soil is kept moist inches below the soil surface, this helps reduce the growth of weeds (also means less water consumption and less maintenance).

Resources

Buried Pot Surrounded By Plants From ecocomposite.org

Here are some reference pages with more details (also make sure to grab the 25 page pdf linked to in the diagram image above)…

ecocomposite.org: Provides a bit of history to this technique and traces it back to over 2,000 years ago (from China). Also gives brief details of how it works and compares its results to other irrigation systems.

Olla Irrigation: (Clay Pot System) Lots of information on this page including a tip to add liquid fertilizer to the water (you’ll need just a quarter to half the amount you would normally use). They also show a DIY using regular clay flowerpots attached to each other using waterproof Gorilla Glue and silicon caulking. They advise painting the top of the Olla with white paint to reduce evaporation (top part of the jar will be exposed to the sun).

More Ideas

Is this clay pot method too much for what you need? Check out these ideas…

lifehacker.com

Automated Drip System: You don’t need to know much about hardware or plumbing, nor do you have to dig any trenches.

After setting up the head, you simply lay 1/2 tubing down and stake it where you’ll want to irrigate. Any place where you’d like to add some water output, you simply puncture the tubing with a specially designed tool, leaving a clean hole.

System is flexible, pretty much leak-proof, and go together like a box of legos.

radmegan.blogspot.com

Coke Bottle Watering Globes: The idea is to fill glass bottles with water and stick them neck down into moist soil. The soil seals around the bottle opening and water releases only as the soil dries. You can use larger bottles (for example wine bottles) if you need more time between refilling.

Here’s a similar idea using 2 liter plastic soda bottles from yougrowgirl.com. This places the bottle neck down as well but has the bottom cut off so you have a large funnel to work with (and collects the rain water too).

shelterrific.com

Iowa Watering Hole Trick: Keep trees and shrubs watered by drilling a hole in the bottom of a 5 gallon bucket, place it near the trunk and fill with water. This will slowly release the water into the soil, reducing the need for soaker hoses.

Supplies needed: A drill with 1/4″ bit, 5-gallon plastic bucket and a hose to fill pail with water.

To keep debris out (and potentially clogging the hole), cover with a piece of board.

csupomona.edu

DIY Bucket Drip: This is a gravity system to feed your drip irrigation system. A heavy pail and a few parts are required, but it’s fairly simple to setup.

Advises that if your bucket is too transparent, the light will encourage the growth of algae so choose a pail that’s dark and won’t let much light in.

Also gives the tip to choose a sturdy object to elevate the bucket since once filled, it’s darn heavy (5 gallons is about 33 lbs.).

craftzine.com

Houseplant Wicking System: The idea is simple yet brilliant: feed water from a bowl underneath (or beside) the plant into your plant’s soil using strips of cotton fabric.

There are two different arrangement examples provided. Very simple way to keep your plants happy and avoid drying out.

This project was previously featured on Tipnut and moved here for better organization.

lettuceshare.com

Wine Bottle Waterer: A simple setup using a wine bottle, wire from a hanging candle holder (or other hanger) and glass flat-backed marbles (to help get the drip right).

howstuffworks.com

Plastic Milk Jug Ollas: Instead of using clay jugs, try this cheap version using plastic jugs instead. Several holes are drilled into the plastic (advises filling containers with water, freezing and then drilling) then the jugs are buried into the soil (same idea as discussed in the article above). Fill with water, twist on the cap and then refill as needed.

veggiegardener.com

Simple Watering Wells: These are made by recycling plastic plant pots (one gallon or half-gallon sizes), bury them in the ground (keeping the rim just above ground level) and then filling with rocks. The water will slowly drip out through the holes at the bottom. Neat idea that’s a lot less expensive to put together than the clay pot method mentioned at top.

suburbanfarmonline.com

Make Your Own Ollas: Here’s another clever & cheap DIY, two terra cotta pots are attached to each other with Gorilla Glue then sealed on one end. Bury in the ground, leaving a couple inches above ground. Water is poured into the top hole (that wasn’t plugged).

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