DIY Olla Pot Irrigation for Containers and Raised Beds

A DIY olla pot is a buried unglazed clay jar that slowly waters roots from below. Make one from two terracotta pots and cut your watering trips.

Quick answer

An olla (OY-yah) is an unglazed clay jar buried in the soil with its neck sticking out. You fill it with water, and the porous clay lets moisture seep out only when the surrounding soil dries. Make a DIY olla by gluing two same-size unglazed terracotta pots rim to rim with waterproof sealant and plugging one drain hole. Bury it to the neck in a container of 15 gallons or more or in a raised bed, and plant 4 to 6 inches away. Expect to refill every 3 to 7 days depending on size and heat.

How an olla actually works

Unglazed terracotta is full of tiny pores. When soil around the clay is dry, water moves out of the pores to even things out. When the soil is wet, little moves. That gives plants water on demand, with far less runoff and evaporation than overhead watering.

Use ollas in containers of 15 gallons or more, in raised beds, or in big in-ground rows. A small 5-gallon bucket does not have enough soil volume to keep the clay working.

Pick the right pots

Buy two unglazed terracotta pots of the same size, 4 to 6 inches across. Check the label. Glazed, painted, or sealed pots will not weep. Stick a drop of water on the outside: it should darken the clay in seconds.

Use a waterproof, non-toxic adhesive such as exterior silicone or marine sealant. Let it cure for 24 hours before you fill the olla.

Where to bury it

Place the olla in the center of a container or between two plants in a bed. Bury it up to the neck. Plants within about 6 to 12 inches draw the most. Farther away, they need hand watering.

Cover the neck with a flat stone or a saucer to keep out mosquitoes and debris.

This is not your problem if

• You grow in small containers under 10 gallons. The soil volume is too small for an olla.
• Your plants are shallow-rooted greens that sit 10 inches or more from the olla.
• Your soil is very sandy and drains in minutes. The water will leave faster than the plants can use it.
• You live where winter freezes the soil. Wet clay cracks. Bring ollas inside before frost.

Step-by-step: make one olla

1. Buy two unglazed 5-inch terracotta pots with drain holes.
2. Plug one drain hole with a cork and silicone, and let it set.
3. Run a bead of waterproof sealant around the rim of one pot.
4. Press the two rims together so the pots form a closed jar. Let it cure 24 hours.
5. Dig a hole just deep enough so the open drain-hole neck sits 1 to 2 inches above the soil.
6. Fill the olla with water through the neck. Cap with a stone.

Water-saving note: gardeners who use ollas often report cutting hand-watering trips to once or twice a week in summer. Results vary with soil and weather.

Olla sizes and what they water

Estimates assume loamy soil, summer weather, and a mid-size container or bed.

Common olla mistakes

Using glazed pots, burying the olla too shallow, and planting too far away are the big three. Also watch for hard water. Mineral scale can clog pores over a season. Rinse the olla with a 1:4 mix of vinegar and water at the end of the year.

Check the water level every few days at first. A new olla can drain a quart in a day while the soil settles.

Myths that waste time

Myth: any clay pot will work as an olla. Glazed and painted pots do not seep.

Myth: an olla replaces all watering. Seedlings and far-off plants still need hand watering.

Myth: you need to bury it deep. Neck up and an inch or two of clay above the soil is plenty.

Myth: an olla uses no water. It uses water more efficiently, but the plants still drink.

Do this today / this week

1. Buy two unglazed terracotta pots and a tube of exterior silicone.
2. Do the water-drop test on each pot.
3. Glue the rims and let them cure for 24 hours.
4. Bury the olla in a container or bed beside your thirstiest plant.
5. Fill, cap, and check the water level in 2 days.

Frequently asked questions

How do you make an olla pot at home?

Glue two unglazed terracotta pots rim to rim with waterproof sealant, plug one drain hole, and bury the jar to its neck.

How long does an olla last between refills?

A small olla may need water every 2 to 3 days. A 1-gallon olla often lasts 5 days in warm weather.

Can I use an olla in a container?

Yes in containers of 15 gallons or more. Smaller pots do not have enough soil for the clay to work well.

Do ollas attract mosquitoes?

Standing water can. Cover the neck with a stone or a saucer.

Key takeaways

• An olla is a buried unglazed clay jar that waters roots slowly from below.
• Use unglazed terracotta only and seal the join with waterproof adhesive.
• Best in 15-gallon containers, raised beds, or in-ground rows.
• Cap the neck and refill every 3 to 7 days depending on size.

Related reading

• Wicking rope: water plants while on vacation
• DIY self-watering bucket planter