How to make DIY Ollas: Low Tech Self-Watering Systems for Plants
Introduction to using ollas in the garden and simple instructions for how to make a DIY olla using a terracotta plant pot. Ollas are an inexpensive way to keep plants watered. They slow-release water around growing plants using an ancient technique discovered by people living in arid regions. Ollas are not only great at keeping plants watered, but they save water too.
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Keeping plants and the garden watered through the growing year can be one of the most challenging aspects of gardening. It takes time, often needs doing daily, and can even be difficult physically. Then there’s water wastage. Much of the water released by sprinklers is lost through evaporation and runoff from foliage and soil. Not ideal from a water conservation perspective and the potential waste of time and money. The goal of watering is to keep plants healthy rather than wasting water. One great way to accomplish this is through using ollas (pronounced “oh-yahs”). They’re an ancient invention and are essentially clay pots that slow-release moisture to plant roots under the ground. Read on to learn more about ollas, how to use them, and how to make a DIY olla using terracotta plant pots.
Ollas are a low-tech and zero-energy required watering system for plants of all kinds. Pumpkins growing in the ground, tomatoes growing in the greenhouse, and even small ollas (or plant watering spikes) for houseplants. Think of ollas as terracotta clay pots that you fill with water and bury in the soil. Unglazed terracotta is porous, meaning that both air and water can travel through the pot. When plant roots are growing near an olla, they sense the moisture seeping through the terracotta pot and grow towards the walls of the olla. They can even latch on and drink directly from it.
What are Ollas
Ollas are clay pots that you bury in the soil at the same level that a plant’s roots grow. Traditional ollas look like urns with a large reservoir for holding water and a smaller neck. Sometimes the neck is flush with the top of the reservoir, and sometimes it’s long so that the olla is better at deep watering. You then fill them with water and seal them with a lid to stop water from evaporating from the top. The water inside the pot travels through the pot’s walls and moistens the soil around it. If plant roots are within reach, they’ll grow up to the pot and can tap into that moisture resource.
The benefits of ollas are many. Instead of watering the soil’s surface, you’re getting water down to the roots where the plant needs it. Effectively, it’s like a constant deep watering if you keep the ollas topped up with water. You’ll also use less water since you’re only filling the vessel with water rather than watering the entire soil area around the plant. Ollas are easy to make from inexpensive terracotta pots and don’t need electricity or gadgets, either. That makes them simpler and potentially more cost-effective than a drip irrigation system.
Terracotta is Porous
Wait, water goes through the pot? Yes! I think it’s difficult for some to understand how water can travel through such a hard material as terracotta. It feels solid and can hold water pretty well so it seems like a strange idea. It works, though, because terracotta is a porous material and the pores in the hardened clay allow water and air to travel through in small amounts. That’s why potting mix in terracotta pots tends to dry out more quickly than potting mix in plastic pots. It’s also why leaving terracotta pots outside in freezing weather is a bad idea. Terracotta absorbs water, and the water inside it can also freeze, causing pots to break.
Since the invention of pottery, people have been using the porous nature of terracotta to their benefit. When water sweats through unglazed clay pots, heat and hot air on the outside cause the moisture to evaporate. As the water evaporates, it cools the air around it, and the pot itself, much like sweating helps to cool our bodies. To this day, unglazed clay vessels are used in arid regions as air conditioners, and low-tech refrigerators called Zeer pots.
How Do Ollas Work
Ollas, made from unglazed clay pots, use that same mechanism but under the ground. Instead of moisture seeping through and evaporating into dry air, it seeps through when the soil around the pot is dry. It does this through a process called soil moisture tension. If it’s been raining, and the ground is wet, the water stays in ollas and isn’t drawn out. When the soil does dry out, water is pulled through and into the soil around the pot. Usually, the moisture doesn’t travel far from the pot and is concentrated in the few inches around the olla. That’s why it’s important for you to place ollas so that plants can grow roots up to them.
Ollas work because plants sense the moisture in the area around the clay pot and grow roots towards it. You can see this happening too! When I dig up ollas from around my tomato plants in autumn, I always notice that the holes left are completely lined in roots. Seeing that has made me realize that the plants’ roots get moisture from the soil around the pot and from the pot itself. During the growing season, the roots cling to the sides of the terracotta and can get water directly from it.
Ancient Clay Pot Irrigation
Ollas are not a new invention, nor only an irrigation method. In Spanish, olla simply means pot or cooking pot, but the use of the word goes back to its roots in Latin. Ollas used in agriculture are unglazed clay pots used strictly for underground irrigation. Evidence shows that ollas have been used to water crops for over 4000 years, beginning in China and northern Africa and then spreading to the new world and other regions. Native Americans also used ollas and may have developed the practice on their own or through contact with settlers. Traditional ollas are still commonly used in India, Sri Lanka, Brazil, Iran, and Burkina Faso.
Ollas are incredibly effective at watering plants while reducing water usage. Because there’s no water evaporation from the surface, moisture stays underground. When plants are grown around ollas, they use the vast majority of the water you pour inside the olla. Very little goes to waste, and you reduce time spent watering too.
How to Use Ollas
Ollas are best suited for watering large vegetable plants such as tomatoes, eggplants, and beans. They’re also great for watering young trees and shrubs in their first year! Smaller vegetables that you grow in rows are less suited for them, though, since their roots may be shallow, and the number of ollas you’d need would transform your growing space into an olla garden! I spread a thick layer of compost as mulch around row-grown vegetables to reduce soil evaporation.
The best way to use ollas is to place one within reach of one to three vegetable plants. For example, a single olla per pumpkin, two tomatoes, or three bean plants. Bury the olla in the ground before you plant your vegetables to ensure that their roots aren’t damaged. Then all you have to do is keep them topped up with water and covered. The cover keeps water from evaporating and stops small animals and insects from falling in and drowning.
I’ve also been asked if you can put plant feed into the water. This may seem clever, especially if you make your own DIY fertilizers, but I’d advise against this. Sure, they’ll pass through the pot’s walls with the water, but they’ll also stew in the pot, making for a pretty nasty experience when you open the olla up next. Best to apply liquid plant feeds directly to the soil above the plant’s roots.
Where to Place Ollas
Once you’ve bought or made DIY ollas, you’ll need to place them in the right spot. That means thinking about how extensive the root systems are of your plants because they need to be reasonably close to the olla for ollas to work. In the greenhouse, I tend to put ollas between my tomato plants, so that’s one olla for two plants two feet apart. It would be one olla per plant for plants that need more growing space, like squash, melons, and pumpkins. I recommend placing ollas a foot away from most larger vegetable plants since their roots won’t suffer from the blockage but can still reach the olla.
You can leave ollas in the ground year-round if your region doesn’t drop below freezing. If it does, make sure to lift ollas and store them in a dry and frost-free place. Terracotta left outside during freezes can crack and break.
How Many Ollas Do I Need for My Garden?
Each garden is different, but if you’d like to use ollas plan to have one per large plant, two medium plants, or a circular row of smaller plants around the pot. The power of ollas is in how many plant roots can grow up and attach to them. For example, a single tomato plant can nearly surround one of my ollas on its own. It takes all the water for itself when it does this, even if there’s another plant close by.
I use ollas in the greenhouse for my tomatoes, and though I companion plant them with basil, I don’t think that the little basil plants stand any chance against the tomatoes hogging the olla’s water. If you wanted to grow smaller plants around an olla, perhaps choose a wide and shallow pot and then sow seed, or plant seedlings, all the way around the pot in a circle. This could be a useful way to grow leafy herbs like parsley and cilantro and could help control premature bolting.
When to Fill Ollas with Water
Your plants will stay watered as long as you keep your ollas topped up with water. The soil on the surface might look dry and dusty, but that underground water reservoir keeps your plants from going thirsty. How often you fill ollas is dependent on their size, the time of year, the plants that are using them, and how dry the soil is. On a hot summer’s day, a small olla placed next to a water-hungry plant will empty quickly. Larger ollas can hold more water and don’t need filling as often.
The DIY ollas I show how to make in the tutorial below are eight inches in diameter and can hold just over two quarts (two liters) of water. In spring, I plant them in the beds where I grow my tomatoes, and at that time, I fill them perhaps once a week. I make sure to open them to check the water level regularly.
In the heat of summer, I tend to fill them with water every two to three days. I’ve measured, and when really warm, the water level in the ollas drops by about an inch of water per day. You can tell that they’re working if the soil around them looks damper than the surrounding soil. I also use the ollas buried in containers rather than in the ground, so they lose water quicker. Containers and raised beds are more open to evaporation than in-ground gardens.
How often you fill your ollas with water will be dependent on different factors, so it’s best to check in on them regularly throughout the growing year. That way, you can understand just how long you can leave them without topping up, were you to go away for a trip. The lid on your olla is also vital in helping reduce watering. A terracotta lid will allow more evaporation than a plastic lid.
Where to Source Ollas
It used to be that many of us would only be able to see ollas in museums. They’ve caught on in the gardening community these past few years, though, especially for people who grow in arid climates. Spain, the South of France, Mexico, Arizona, California: these are places where ollas can really make a difference in the garden. I live in a temperate climate but still find ollas extremely useful in my greenhouse.
If you buy ollas for the garden, they can be beautiful but very pricey. Always on the lookout for a low-cost solution, I’ve thought up a way to create DIY ollas using ordinary terracotta plant pots and saucers. In the video and instructions below, you’ll learn how to convert them into low-tech watering solutions for your plants and garden.
How to Make DIY Ollas
Equipment
- Spade to dig the olla into the ground
Materials
- Unglazed terracotta plant pot the larger, the better
- Plant pot saucer (plastic) that fits as a lid
- Material to seal plant pot drainage hole cork, mounting putty, other
Instructions
- Choose a terracotta plant pot that can hold at least a quart of water, if not much more. Ensure that it's unglazed – so no paint or glaze on any part of it – otherwise, water will not be able to travel through to the soil. Remember, a larger size olla can last much longer between refillings. Smaller ollas can be more effective for smaller spaces though.
- Most plant pots have a drainage hole at the bottom. Fill this hole so that water cannot leak through. I've tried various materials, and my favorite solutions are non-toxic mounting putty and a cork. You could remove either and use the pot used for plants again if you wanted to. Duct tape works, too, as does moldable putty that hardens. A more permanent solution is to fill the bottom of the pot with concrete*. I made one like this seven years ago, and it works a treat!
- Next, bury the pot in the soil within about 6-12" of where you plan on growing a plant. Ensure that the neck of the pot is above the soil surface.
- Fill with water and place a lid on the DIY olla. A lid reduces surface evaporation and stops animals from getting into the olla. Small animals can drown in them when the water level isn't full to the top. Mosquitoes and other insects can get inside to breed too. I used terracotta plant saucers in the past, but I've found that plastic ones work much better.
- Plant your crops within roots' range of the olla and keep them watered from the surface until they're established. Keep the olla topped up that entire time so that the plant senses the water source and can grow roots towards it.
- Top up the olla so that it never empties. The frequency of filling times varies based on the size of the olla, time of the year, number of plants planted around it, and other factors.
Video
Notes
Smart Gardening Ideas
Using and making ollas is a smart way to reduce the amount of water, and time spent watering, in the garden. Here are even more ideas that help you to grow bountiful harvests while saving time and effort:
- 70+ Perennial Vegetables to Plant Once and Harvest for Years
- Time Saving Gardening Tips and Tricks for The Lazy Gardener
- Use Black Plastic to Kill Weeds
We’re trying these out for the first time this year so far I’m loving it (as are the squashes we put them with). One question- the roots of one of my courgette are invading its olla pot – do you think it matters? Thanks
All of your plants will grow their roots right up to the pot with time. They’re like moisture-seeking missiles! It’s completely normal and what you want :)
You are mistaken about the origins of the word “olla.” Rather than Latin, “olla” comes from Arabic. In Arabic, “olla” is the word for the large clay vessel we know with the same name. It’s an old Arabic word that is still used today. I’m interested to know the source of this word’s incorrect etymology. These vessels are still commonly used in the Middle-East for farming and also have a more visible everyday use that has changed very little for centuries. “Ollas” were the drinking fountains of the ancient past. Today, as back then, they are often placed on stands at corners or near homes or shops. They are filled with water and outfitted with a cup or dipper for the public to drink from. Since the Middle-East is very hot one can understand the utility of this custom. Thank you for your post.
I made ollas for my tomatoes and placed them as directed in the video, and have covered them with rocks on top. Somehow the earthworms keep finding their way into the pots. I am constantly rescuing worms from drowning, but can’t save them all. I’m worried that I am losing too many worms in the ollas, and I feel badly:( Suggestions?
I’m so sorry to hear that! Slugs are attracted to the sides of mine too and I sometimes find them inside, but not dead. If you’ve not done so already, make sure that the lip of the olla sits about an inch from the top of the soil’s surface. For a lid, choose a snug one and these days I use plastic pot saucers since they help reduce water evaporation from the top.
Thanks for the great article. I am having trouble though. I bought Pennington unglazed terracotta pots from Walmart. I closed the hole with putty and filled it up. The water line did not move at all and there was no water around the pot. I buried it, same thing. I have a small olla bottle from Back to the Roots. It works perfectly. What am I doing wrong?
I’m not familiar with the Pennington pots but it seems that the only issue could be with them. Try another pot – generic terracotta pots are best.
Awesome! The armchair scientist in me is curious how much water a tomato, pepper, broccoli, etc actually draw up each day, and if the olla oozes enough to the roots removing the need to ‘hose’ water. What size were the terracota plants in your video? The saucers around here are all terracotta…where would a person find a plastic lid the right size to make a tight seal (the pot saucer would be looser). Great video!
It really depends on the plant, climate, temperature, size of plant, time of year, and so many factors. A small tomato plant in spring will use less water than a mature tomato plant in summer. My ollas are about 8-12″ in diamter. Here’s where you can buy plastic pot saucers.
Also, ollas seep water slowly but that’s not really how plants access the water source. They sense the moisture being released and then grow their roots up against the pot. In ollas, plant roots pull water directly from the pot. So if your plant is too far away that it can’t grow its roots up to the pot, then the olla is of no use.
I just learned of Lola pots.
I’d like to use them by my established perennials & roses. I think they would be more lush w an additional water source, esp in the harder to water areas. Your thoughts? I’m in Western SD so it definitely freezes in winter.
I’m stumped on the size & Esp stumped on the needing to dig them out every winter- then refrig them back in, in the spring. Maybe they aren’t a good idea for perennials???
They are a good idea for perennials in climates that don’t freeze. You’ll likely need to lift your pots each winter and store them somewhere frost-free to keep the terracotta from freezing and potentially cracking in the ground. Digging them up from around perennials can disturb the roots. Drip irrigation may be a better solution for your roses and perennials!
I went to the dollar store, picked up some terra cotta pots and dish along with sticky tac.
Made the ollas today and stuck them in the garden. I am hoping it works well.
Hi! How could I utilize olla pots for a large 3 compartment fabric bag that I have . I have 1 tomato plant on the ends but the middle compartment is empty. Could I use a olla and place it in the middle compartment? Even if there are fabric walls separating each compartment? These a adult plants at this point.
I don’t think that would work — the fabric walls would inhibit plant roots from being able to access the olla in the middle compartment.
I meant to make ollas to plant with three lavender shrubs. If I remove them in winter will it hurt them? Thanks
Hi Marilyn, lavender is pretty hardy and drought-resistant — you most likely don’t need to use ollas with them. If you did, I don’t see that removing them in winter would harm the plants. As long as you refill the hole with firmed in soil so that the cold doesn’t get down to the lavender’s roots.
This is just an idea I came up with because I like to repurpose instead of throwing away. Repurposing is just a way to get more for your money. I believe in the philosophy of spending once and using it 2 or 3 times. Several years ago I decided to repurpose my gallon milk and distilled water jugs for the garden. I put 4 holes in the bottom corners(1 in each corner) then cut out the opening of the bottle to about 2 times bigger than it was so it would be easier to fill with the water hose. Now granted it is plastic so the water can not got thru the sides, but I only put them as deep as the straight side walls. They lasted a couple of years before the sun would make the tops brittle. Going into the 3rd season, I would have plenty more jugs to replace those that were brittle.
Hello! I am in zone 7a and also a huge fan of ollas. Last year I read this post and loved it! But I was trying to think of a way to be more efficient with space for the olla to plant ratio. Have you ever tried terra-cotta watering spikes? They are essentially an olla on a smaller scale. You place the terra-cotta spike into the soil as you would a traditional olla, and the place a bottle filled with water upside down into the opening. I have found this works really well for multiple reasons. Because the bottle is above ground, you can see the water levels as the ground absorbs the water so you know when to refill without having to constantly check into a pot. Also, the spike is tremendously space efficient and I can place however many I would like amongst the plants. This can also pose a downside as the smaller size means less water and more frequent fill ups, but that also depends on the site and how the ground absorbs the water. Generally even in the hottest and driest months of summer, each bottle is filled maybe twice a week (about an 8oz glass soda or water bottle – also a great way to reuse materials). My tomatoes, cucumbers, and watermelon (all very thirsty plants) did amazingly well with this method.
Just thought I would pass this along. I would love to know what you all think and if you have tried this as well!
Will this work for potted trees?
There are probably better waterers for potted trees and container plants out there than these. A wine bottle filled with water and popped into the soil for one! Ollas are better for in-ground, raised beds, and large planters.
What an awesome idea. Summer is practically over, but I want to try this for next year. Do you think it would work with bucket plantings too? Maybe use a smaller size pot next to the edge of the bucket? Thanks!
Olla’s have made the world of difference to our large garden. I use little ones like this with the lid in stryrofoam boxes with my seedlings. Thank you for the blu tak tip! I was using cork but they are hard to come by. I in the middle of four seedlings seems sufficient.
I have since connected 2 pots together and fill them via drip irrigation tubes and t-connectors slotted into the hole of each top pot, that are all fed by gravity water collection barrels off the roofs of surrounding chook and garden shed. I just turn on the barrel faucets to fill rather than carrying buckets (only because my garden is an acre)!
Eva, this is a great idea, thanks for sharing!
Eva, can you send me a picture of your set up? I’m having a hard time visualizing (sorry). My garden is also large, and far away from the house, so I also use rain barrels to water it.
Thank you in advance, Jeanne
Thanks – I always was going to make my own olla by “gluing” 2 pots together.
But just using one pot with maybe a cork in the bottom and a clay saucer might be a lot simpler – especially if one can spare a few more feet in their garden that wider-mouthed pot might use
Absolutely :) Also, most plant roots will grow the depth of a single pot rather than the depth of two. The way ollas work is not to water the soil but to create a reservoir for plant roots to latch onto and drink from directly. If you use an olla, have a close look at the end of the season when you pull it out of the ground. It will have roots all over it!
Do you need to remove the pots in the winter if your garden is prone to frost or freezing?
Yes, if you’re worried about that, and your area has freezing temperatures in winter, it’s best to store them in a shed or at least outdoors raised off the ground.
I just started with option 1 yesterday in middle Tennessee, raised bed. An 8 quart pot with the infomercial waterproof tape that I have a leftover roll of. It is within a foot of 4 small tomatoes and a squash plant. It may overtax the olla but the water held overnight. I watered yesterday before trying the olla and our soil is still a little damp from extensive rain and lower than normal night lows and daytime highs this spring so I expect wicking to be a little slow for a few days. Exciting experiment. Now if I can just figure out hydroponics for some lettuces and greens in our little Aldi bought greenhouse.
We have done this with our raised beds for the last couple years. The ollas work great. I use a bigger size with tomatoes and larger vines and smaller ones distributed through beds for things like strawberries. I still water at the surface level many times in our hot summers and I have some recessed plastic pots with holes near tomatoes for deep watering once a week or so. But it’s really nice to know that they have a consistent, slow release option to keep them from drying out.
I’m thinking in the future I might run rope or nonwoven tote bag material out of them to enhance the wicking effect. Have you ever tried this?
So good to hear! With ollas, the idea is that the plant roots latch onto the sides of the terracotta and draw water directly through it. No wicking through fibers is necessary :)
Will liquid fertilizer leach through the pot. I use a kelp base fertilizer for some of my veggies. Thank you!
I wouldn’t advise it since the standing water inside the pot, and the pot itself, will get mucky and filled with algae and unwanted microorganisms.
why do you need to pour concrete in the pot? wouldnt it work otherwise? thank you
I believe the author was just presenting an alternative for those who were looking for something more permanent.
Terracotta pots normally have a drainage hole in the bottom, so without something to plug this hole all the water would quickly drain out the bottom instead of slowly seeping through the clay.
Correct :)
To stop the olla from sweating through the bottom. You want the roots to reach the water through the sides of the olla.
I’m just wondering what kind of surface area one pot would cover?
It doesn’t water the soil in that way since only the inch or so around the pot will be moist. Plant roots will seek out the moisture and eventually latch onto the terracotta pot. Place an olla about a foot from each of the plants you want to keep hydrated.
Can I get clay pots anywhere? Or do I need to make sure that I purchase them from specific places? I want to make sure I know if some have lead, or something. And, are terra cotta pots generally unfinished? Sorry if these are silly questions. Thank you. Your post is great, and very helpful!
You can get unfinished terracotta pots from many places. They’re made for the garden and do not contain heavy metals like lead, so don’t worry.
I hope you found some terracotta pots!
If by chance you haven’t, they can be found in a multitude of places.
-Walmart or Target Garden Centers
-Craft Stores ie:
•Michael’s
•Hobby Lobby
•JoAnn’s
-Any local Nurseries
I hope this helps you and any others that may see your question.
The Home Depot and Lowe’s too.
Very helpful, thank you!
Thanks so much for this video. I’m doing this tomorrow. We are on level 4 water restrictions in NSW, Australia due to drought and can’t use hoses at all now. No rain in sight either. Thanks again.
You may have to soak the whole thing in water first. I don’t know why, but terracotta sometimes needs to have water thoroughly permeating it before it can wick efficiently. Other times it doesn’t. Who knows! Happy gardening!
I have an old Terra gotta pot that I used a few years ago, and then after the season I stopped using it. I decided to put it to use again, but I can’t tell if the soil is absorbing anything. I feel around the pot but it feels dry and the soil around it is not really wet. I know it’s not glazed. It is because the pot is old?
Maybe the pores are closed up. Might need unclogging first with some vinegar and water and soaking or something along those lines.
I love this. Very nice and classy.
I was thinking about using wine bottles, since I recently discovered how plant nannies work. Do you think I could just put some putty in the wine bottle and poke a hole through it? It would be a botella instead of an olla!! :)
Thanks for your help!
Hi Melanie, I’m not sure the putty would work well but you can get terracotta fittings to put over the neck of a wine bottle. They make them into instant plant nannies.
Funny that the word for bottle in Spanish is botella and also olla is Spanish for pot.
How big an area will one pot, the size in the video, service?
It’s less about the area and more about the plants. You should aim to have your pot within reach of the roots of 1-2 [tomato] plants. They’ll grow onto its surface underground and drink directly from the pot.
Thumbs up. Love the planter watered
What a wonderful idea. I love it. The lids can be removed during a rain to collect rain water and being even more conservative. I’m excited to make my own and get them in the garden. Thank you for sharing this fantastic idea.
You’re so welcome Edith :) Good idea for rain collection too!
I actually used plastic lids and picked holes in them so when it rains it will collect water
I have extremely hard water. Will it keep the pot from sweating?
Good question! The minerals in hard water has a tendency to accumulate on the outside of terracotta pots. I’m not sure if it will stop moisture from seeping through, though, but imagine that it would. If in doubt, use rain water for your ollas.
Good question! The minerals in hard water has a tendency to accumulate on the outside of terracotta pots. I’m not sure if it will stop moisture from seeping through, though, but imagine that it would. If in doubt, use rainwater for your ollas.
I make my olla’s out of two terra-cotta pots siliconed rim to rim and fill them through the hole on top. I just silicone a small tile in the bottom hole to seal it. Then cover the top with a saucer to keep the dirt out.