By Emily How, Horticulture agent

NDSU Extension – Ward County

“I may have messed up,” I confessed to my mother over the phone a few weeks ago.

In my springtime excitement, I had planted my radishes and spinach in an elevated bed. My mistake came from not checking my calendar. I was planning on being out of town for the next week and a half. Seeds were already planted, and I had no way to water them.

“Just use an olla,” my mother responded. She had just finished her Master Gardener course in Texas and was excited to tell me all she had learned.

Olla, pronounced “oy-ya,” means “pot” in Spanish. Olla is an old irrigation method that was very popular a few years ago and even spurred a previous Dakota Gardener article. The process is simple: use an unglazed clay pot, fill it with water and let the magic of capillary action do its work.

If the soil around the clay pot is dry, the water will transfer from the pot to the soil through the small pores in the clay pot. For this reason, the pot must be unglazed clay. Water cannot pass through a glazed or plastic pot.

Traditional ollas are jugs with a wide base and a narrow neck with a cover on top. You can buy a traditional olla, but I was in a rush, and these ollas needed to get into the garden bed immediately. Once again, Mom came to the rescue with her newfound Master Gardener knowledge and told me how to build one.

There are two popular ways to build an olla at home. The simplest method is to bury a clay pot, leaving one inch above the soil, then plug up the bottom hole with something like a ceramic tile so the water cannot run through. Fill with water and cover with a pot lid. Weigh down the lid with a rock or other heavy object and then just check the olla to see how often you need to refill the olla.

The second way is to get two clay pots of the same size and glue the tops together with a silicon glue (often found in the plumbing section). Use silicon glue to plug up one of the holes. Let the silicon cure, then fill with water by submerging in a bucket of water. Bury the glued pots so that the top of the unsealed pot is 1 inch above the soil line. You can use a drill to widen the top hole, but I have found that my hose on low pressure fills the olla pot just as easily.

So how many ollas does one garden need? According to the University of Arizona Extension, the olla will cover an area two times the diameter of the pot. So, one 6-inch pot will cover one square foot.

Did this work? Yes! I came back to a garden full of radish and spinach sprouts looking happy and healthy. Ollas are a great way to keep my elevated bed watered through the summer, since it tends to dry out more quickly than my in-ground garden. This method can also be used in flower pots or other areas that may be difficult to keep watered.

One word of advice: do not use this method with woody perennials or trees, as their roots can break the pot and leave a mess in your soil.

NDSU Agriculture Communication – May 26, 2026

Source: Emily How, 701-857-6444, emily.how@ndsu.edu

Editor: Dominic Erickson, 701-231-5546, dominic.erickson@ndsu.edu