ByTanya Anderson October 7, 2024October 8, 2024

How to Make DIY Ollas Using Terracotta Plant Pots

151K Shares

This website is reader-supported - thank you! As an Amazon Associate I earn from qualifying purchases.

How to make ollas using terracotta plant pots and tips on using them in the garden. Ollas are inexpensive gardening tools that keep plants watered, even in the driest climates. They slow-release water to plants using an ancient technique, all while using no electricity and reducing the amount of water you need for your garden. They’re also incredibly easy to DIY!

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 from sprinklers is lost through evaporation. It’s not ideal from a water conservation perspective and is a potential waste of time and money.

One great way to keep plants watered while saving time and water is by using ollas (pronounced “oh-yahs” or “oya”). They’re an ancient invention, essentially unglazed terracotta pots that slow-release moisture to plant roots underground. They’ve been around for so long because they work and are cheap to make! You fill them with water from the soil surface, and they create an underground reservoir of water that plants can use. Best of all, you can make DIY ollas using old terracotta plant pots and other inexpensive materials. Read on to learn how.

Ollas: Ancient Clay Pot Irrigation

Ollas are a low-tech watering system for all types of plants and gardens. They’re not a new invention; evidence shows that ollas have been used to water crops for over 4000 years. They likely originated in China and northern Africa and then spread to the New World and other regions. In Spanish, olla 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.

The view of a small raised bed with tomatoes and basil planted inside. There are also two terracotta pots buried in the bed. One is covered by a terracotta lid, while the other is open and being filled with water from a watering can. — Ollas help water your plants by slowly releasing moisture into the soil.

You can use olla in traditional garden beds, raised beds, container gardens, and even indoors. However, the most common way to use them is in the vegetable garden. Pumpkins growing in the ground benefit from them, as do tomatoes growing in the greenhouse. They’re useful for growing any vegetable that needs a lot of moisture or grows in soil that dries easily. Small ollas called p lant watering spikes are even becoming popular for houseplants.

Using Ollas

To use ollas, you bury them in the soil so that the water they contain sits at the same level that a plant’s roots grow. Traditional ollas look like urns with a large round reservoir for holding water and a narrow neck. Sometimes, the neck is short and flush with the top of the reservoir. Sometimes, it’s long, so the olla is better at watering deeper roots. Either way, you bury them so that only the top inch or two pokes up from the soil.

A woman plants tomatoes in a raised bed alongside DIY ollas that look recently installed. — Sinking the ollas in the bed, then planting tomatoes nearby

You then fill them with water and seal them with a lid to stop water from evaporating from the top. For the DIY option, this lid is a plant saucer. For modern commercially-made olla s, it could be a terracotta or plastic lid. Then, underground, the water inside the pot travels through the terracotta and moistens the soil around it. If plant roots are within reach, they’ll grow up to the pot and latch on, drawing moisture directly from the pot.

Benefits of Ollas

Instead of watering the soil’s surface, ollas help you deliver water directly to the roots. That means you can bypass watering the soil around plants and stop losing moisture to evaporation. Though you can now buy very effective and modern olla irrigation systems, ollas are also easy to make from inexpensive terracotta pots. That makes them simpler, more accessible, and potentially more cost-effective than drip irrigation.

Water Seeps Through Terracotta

Ollas are always made from unglazed terracotta, and both sides of the pot must be unglazed. They could be custom-made pots, spikes, cups, or cheap terracotta plant pots. Though the material looks solid, terracotta’s structure is like a microscopic mesh that allows moisture to seep through. I shared a time lapse showing how this happens a couple of years ago. It doesn’t take long for a terracotta pot filled with water to become damp outside! The pots don’t leak puddles of water but release enough for the soil to start absorbing it, which kickstarts the wicking process.

The view of a water-filled DIY olla from above. You can see white putty covering the plant pot hole at the bottom. — Water will seep from inside the olla to the soil surrounding it.

This wicking is done through a process called soil moisture tension. The soil’s moisture level wants to be similar to the moisture level inside the pot. So, if it’s been raining and the ground is wet, the water stays in the ollas and isn’t drawn out. When the soil does dry out, water is pulled through the porous terracotta and into the soil. Usually, the moisture doesn’t travel far from the pot and is concentrated in an inch or two around the olla.

Bury Ollas First, Plant After

When installing ollas, it’s best to bury them in the ground first, then plant crops near them. That way, you won’t damage plants or root systems, and you can get your spacings right. If a plant’s roots grow long enough to reach an olla, it can benefit from its moisture. If the roots can’t grow that far, the olla won’t help the plant. Regardless, you need to manually water plants until they grow large enough to establish and grow an extensive root system.

Traditional olla pots as round vessels with narrow necks. — Traditional ollas have a small neck that pops up from the soil. Credit

Also, ensure that the neck or rim of the olla pokes up from the ground when you bury it. This makes it easier to fill and helps keep soil from falling inside. Once filled, ollas work because plants sense sources of moisture and grow their roots towards it. When I dig up ollas from around my tomato plants, the holes left are completely lined with roots. Seeing that has made me realize that the plants’ roots get moisture from the soil around the pot but also from the pot itself.

Did you know that unglazed clay vessels can be used as low-tech air conditioners and refrigerators? They’re called zeer pots and work through the moisture on terracotta pots evaporating in hot temperatures. This process cools the air around the pot, much like sweating helps to cool our bodies.

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. You can grow smaller vegetables around them, too, but you’ll need to plant them within a couple of inches of the pot. I’ve squeezed five lettuces around a large one before and two chard plants around another. I also found that watercress thrives around ollas. They love moist soil, and I have a big sprawling plant growing around an olla in one of my Birdie’s beds.

A plastic plant pot lid sits on the ground as a lid for a DIY olla. A brick holds it in place while five lettuce seedlings surround it. — Lettuce seedlings growing around one of my DIY ollas.

The best way to use ollas is to place a large one within roots’ reach of one to three vegetable plants. For example, a single olla holding about a gallon (4 liters) of water per pumpkin, two tomato plants, or three bean plants. Bury the olla in the ground before you plant your vegetables to ensure their roots aren’t damaged. Then, all you have to do is keep them filled with water and the opening covered. The cover keeps water from evaporating and stops small animals and insects from falling in and drowning.

A woman holds the lid of a DIY olla and looks down at the water-filled pot. — Place ollas within the roots’ reach of the plants you want to water.

I’ve also been asked if you can put plant feed into the water. This may seem clever, especially if you make DIY fertilizers, but I’d advise against it. The nutrients will 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 using a watering can.

Distance Between Ollas and Plants

Ollas need to be reasonably close to plants for them to work. If they’re not within reach of a plant’s roots, the olla cannot benefit the plant. This means you’ll need to understand the sizes of root systems of different crops. Also, some crops have big root systems that will swamp out other plants. You may intend to use a single olla to water multiple plants but it could turn out that only one benefits.

DIY Olla Watering Pots -- a low-tech solution that keeps plants watered in dry conditions. Also saves time and water. — One two-quart olla is good for two tomato plants.

In my garden, I tend to put one medium (2 quarts) DIY olla between two tomato plants. So that’s one olla servicing two plants planted two to three feet apart. I’d use one large olla (1 gallon) per plant for those that need more growing space, like squash, melons, and pumpkins. I recommend spacing DIY ollas a foot away from most larger vegetable plants.

A flat rock serves as the lid for a traditional olla with a narrow neck. — A flat rock serves as a lid for this olla. Credit

I sometimes also use DIY ollas to grow smaller crops, like lettuce or basil. Once it’s buried, you can plant seedlings or sow seeds around the pot’s edge. Since their root systems are smaller, lettuce, leafy herbs, and other salad greens must be within a few inches of the olla. Four or five plants per olla is fine if you can still get the olla lid up to water it. If an olla is so close to a plant that it’s difficult to open and fill it, it could be an issue.

Spacing is more Flexible with Olla Cups

Not only do I use handmade ollas, but I also use purchased ones. When I installed the Thirsty Earth olla system, I buried the cups zigzagged along my raised beds about two feet apart. Each year, when I plant the beds, I plant the young plants within about six inches of them. Most could be a little further away, but it’s a space conservation decision, too. The tops of the ollas often get covered in bushy plant growth, but this is not an issue. The cups are drip-fed with lines, so I don’t have to manually water each.

Olla Sizes

Traditional ollas are often large pots holding anywhere from one to eleven liters (one quart to three gallons) of water. If you’re in the market to buy ollas, the bigger, the better, in my opinion. Solitary one-liter ollas aren’t that big and would probably only be suitable for a single Swiss chard plant (or similar-sized plant). Try to use it with a squash, and you’ll be refilling it every day in the summer. Not much time-saving there. The cups in the Thirsty Earth system I use only hold half a liter (2 cups), but they’re constantly fed with water via a drip line. As long as the big water reservoir they’re attached to is full, so are the smaller cups.

A young eggplant is planted a few inches away from an olla cup. A black plastic line attaches to the cup then moves on out of view. — Drip lines keep the ollas in my Thirsty Earth system filled with water.

For DIY ollas, the pot you choose should ideally be able to contain at least two quarts (2 liters). A full gallon (4 liters) is even better. Smaller containers need to be filled with water more often, and the smaller surface area means fewer roots can attach to the pot. If you use smaller pots, they probably won’t be as effective. In addition to needing filling more often, they won’t be able to water as deeply.

How Many Ollas Do I Need for My Garden?

If you’d like to use DIY ollas throughout your garden, plan to have one large (1 gallon) olla per large plant, two medium plants, or a circular row of smaller plants around the pot. That can mean quite a few ollas, but you’ll have more space to work in an open-ground garden. Raised beds will have less internal space, and you want to ensure that plants have enough space for their roots to grow. You’ll need a more creative planting design or invest in a drip-fed olla system.

Two large raised beds in a polytunnel filled with olla cups. They are spaced out on the surface and about to be dug in. — Spacing out my drip-fed olla cups before burying them.

I use DIY 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. A wider pot could be better if you wanted to grow smaller plants around an olla. Then, you could sow seeds or plant seedlings in a circle around the pot. This could be a useful way to grow leafy crops like lettuce and cilantro and help control premature bolting.

When to Fill Ollas with Water

Your plants will stay watered if 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 depends on their size, the time of year, the plants 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.

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 #irrigation #gardening #watering — I fill my ollas every few days during the growing season.

To understand how often to check your own ollas, it’s best to check in on them regularly throughout the growing year. Your garden, climate, plants, and ollas may be different from mine, so they may need a different watering schedule. Figure that out, and you’ll know just how long you can leave them without topping them up. That could be very useful for when you’re planning a trip. Another thing to know is the type of lids you use can impact how often you’ll need to fill your ollas. A terracotta lid will allow more evaporation than a plastic lid.

Two terracotta pots sitting on the lawn with terracotta plant pots serving as lids. — You can make ollas using unglazed terracotta plant pots.

As for the DIY ollas I make, they are eight inches in diameter and can hold just over two quarts (two liters) of water. In spring, I bury them in the beds where I grow my tomatoes and check the water level regularly. In the height of summer, the water levels in the ollas can drop by about an inch a day. Ollas buried in containers tend to lose water quicker than those in the ground, so you may find that the same ollas need less refilling in your garden.

Where to Source Ollas

It used to be that many of us would only be able to see ollas in museums. However, they’ve caught on in the gardening community these past few years, especially for people who garden in arid climates. Spain, the South of France, Mexico, Arizona, and California – these are places where ollas can make a real difference in the garden. I live in a temperate climate, though, and I still find ollas extremely useful.

A woman's hand holds a tall terracotta cup from the Thirsty Earth olla system. — These olla cups get gravity-fed water from large tanks.

If you want to start using ollas, there are a few options. You can make them yourself using terracotta plant pots, which is both easy and inexpensive – instructions are below. If you’d prefer, you can also buy olla pots and olla watering systems.

Tomato plants and lettuce growing in a raised bed filled with olla cups. — Tomato plants spaced about a foot from the ollas.

Individual olla pots can be beautiful but very pricey. Another option is the olla watering system from The Thirsty Earth. They’re a system of small olla cups connected by gravity-fed lines that distribute water from a larger reservoir or your mains. That way, you don’t have to manually fill the pots themselves. If you buy this system, you’re welcome to use my discount code lovelygreens for 10% off.

Overwintering Ollas

Once buried, you can leave ollas in the ground if your soil doesn’t freeze in winter. If it does freeze, lift the ollas and store them in a dry, frost-free place. Terracotta left outside will absorb moisture, and if it gets cold enough, it can freeze, crack, and break. You can rebury ollas in spring before planting. Now, on to how to make DIY ollas…

More Smart Gardening Ideas

70+ Perennial Vegetables to Plant Once and Harvest for Years
DIY Self-Watering Planter (easy project)
How to Use Black Plastic to Kill Weeds
Make DIY Seed Starting Containers

How to Make DIY Ollas

Tanya Anderson

Transform simple unglazed terracotta plant pots into DIY ollas. Use 6" or 8" pots, a saucer that will fit over the top as a lid, and your choice of material to fill the drainage hole. Situated near crops, these slow-release waterers will help reduce water usage and time spent watering the garden.

5 from 6 votes

Print Project Pin Idea

Author Tanya Anderson

Cost $5

Equipment

spade (to dig the olla into the ground)

Materials

unglazed terracotta plant pot 2 quart (2L) capacity or larger
plant pot saucer plastic is best, but terracotta works
mounting putty or a champagne cork, concrete, or another material to fill the plant pot's drainage hole

Instructions

Choose a terracotta plant pot that can hold at least two quarts of water. A larger sized olla can last much longer between refillings. Smaller ollas can be more effective for smaller spaces and raised beds, though. Also, ensure the pot is unglazed – no paint or glaze on any part of it. Otherwise, it will not work as a DIY olla.
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 champagne cork. You could remove either and use the pot used for plants again if you want to. Duct tape works, too, as does moldable putty which 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 the DIY olla with water and cover it with a lid. I used terracotta plant saucers in the past, but I've found that plastic ones work much better.
Plant your crops within 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 fully 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

* To make a permanent olla, fill the bottom of a terracotta pot with about an inch of concrete. In my experience, the concrete hasn’t affected the pH of the soil.

Tried this project?Let us know how it was!

Pin151K