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Ollas? Oh, Yeah!
Sometimes the oldest and simplest approach is still the best. (Used a wheel lately?)
Now, one ancient irrigation technique is making a comeback in New Mexico, California, and other drought-prone climates.
Irrigation with ollas (unglazed clay pots) is simple and extremely efficient, but the system gave way to modern watering techniques in New Mexico decades ago, said Curtis Smith, a horticulture specialist with New Mexico State University’s Cooperative Extension Service.
Under the system, gardeners fill unglazed clay urns with water and bury them near plants. The water slowly seeps through the porous clay, directly irrigating roots. The tops of the ollas (pronounced OH-yas) extend above ground so the urns can be refilled as water is absorbed.
Since roots grow in search of water sources, they usually form a dense, fibrous mat around the olla for a very efficient water delivery system. Ollas virtually eliminate the runoff and evaporation common in modern irrigation systems, allowing the plant to absorb nearly 100 percent of water, Smith said. "Ollas are about the most water-efficient irrigation method available, and they’re incredibly simple to use."
Unfortunately, ollas can be hard to find. Smith partnered with a ministry and a nonprofit organization to establish a small olla factory in New Mexico. Seed and Light is a charitable organization that helps low-income communities worldwide improve agriculture by adapting low-cost, alternative technologies. The organization has helped introduce ollas in arid, developing countries like Afghanistan and Kenya.
To make the urns, the ministry created plaster of Paris molds from pumpkins, squash and gourds of various sizes. Workers pour liquid clay into the molds to shape the urns and then fire them in the kiln to solidify the clay. The urns retail for $12 to $15 depending on size, and proceeds help pay for ministry services, including Spanish-language educational programs.
Are ollas appropriate for Austin? Absolutely. "In places with water conservation ordinances, ollas can help maintain a steady flow of water to plants because the urns only need refilling once or twice a week," Smith said. "It’s also good for people who go on vacation or who have busy schedules."
However, proper plant and olla selection is important. Gardeners should choose low-water-use, nonwoody plants, because woody plants can break clay urns as their roots grow, Smith said. They should match olla porosity, size and shape to plants’ water needs, root size and root distribution. Above-ground portions of the olla should be glazed or treated to prevent evaporation. And gardeners need to place a cover over olla tops to avoid creating a mosquito breeding site.
Supply is still an issue for Austinites interested in ollas. Some New Mexico artisans have begun to create and sell handcrafted clay ollas for use in landscapes and container gardens. Other gardeners, including some in El Paso, are finding simpler ways to approach the problem by making their own modified ollas.
To make these improvised ollas, gardeners seal two unglazed clay pots with a silicone adhesive. They seal the drainage hole on one pot (the bottom) and leave the other open, sometimes widening the hole for easy filling. The container is then buried in soil, leaving about one inch above the surface, and filled with water.
Creative gardeners are even decorating these makeshift ollas with stones or sea glass to make objects d'art. Sealant is used to attach the decorations around the filling hole, or to a saucer used as a lid. The decorative cover keeps mosquitoes, other insects and debris from getting into the water.
Ollas also do a great job of weed control -- since the water goes directly to the desired plants, less is available to nourish weeds. That may not be as evident here in Austin, where we can expect more natural rainfall. On the other hand, we may not need to fill our ollas as frequently. Some gardeners have found that keeping the ollas filled helps prevent salts in the water from clogging the porous clay, which may be a concern in Austin.
We're still learning about ollas, too, so we're interested to hear your experiences and thoughts. Let us know if you try an olla in your garden!
[PRINTER FRIENDLY VERSION]
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