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.
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.
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.