Olla gardening by Curtis W. Smith, NMSU Extension Horticulture Specialist
Irrigation of plants by means of ollas, unglazed pottery jars, is an ancient practice. It was brought to the American Southwest by Spanish settlers and adapted to local gardens by Native American gardeners as well as by the Spanish settlers.
Over time, modern systems were adopted, but these modern systems are not as efficient as irrigation by seepage from buried ollas. Modern systems, even surface drip irrigation systems loose more water to evaporation and more likely to clog than ollas. When ollas are used properly, plant roots will proliferate around the moist clay jar, intercepting water before it can move through the soil by capillary action. This water intercepted by plant roots will then be used in the plant transpiration stream. This results in almost 100% of applied irrigation water being absorbed by the plants.
Olla irrigation solves problems for gardeners who cannot irrigate frequently, and is a boon for plants that should not be irrigated frequently. Ollas allow gardeners who travel as well as gardeners whose irrigation frequency is limited by water conservation ordinance to irrigate infrequently while still maintaining the health and beauty of their garden plants.
Proper plant and olla selection is important. Woody plants may break the pottery jars as their woody roots grow in diameter. Herbaceous plants are less likely to damage ollas. Olla porosity, size, and shape must be matched to plant water needs, root size and root distribution. Deeply rooted plants benefit from deeper ollas, shallow rooted plants are more efficiently irrigated with shallow ollas. The diameter of the olla may also be chosen to match the diameter of the plant cluster. Shallow, broad, ollas will provide adequate irrigation for clumps of grasses and annuals,
Olla plantings should be planted in clusters to maximize water use efficiency. While the planting group may be of one plant type, mixtures of grasses, annuals, biennials, and perennials may also be planted around a single buried olla. Mixtures of plant types may be used to create a more natural landscape. The olla clusters may themselves be clustered to create more expansive or linear plantings.
The olla pottery may become a decorative element in the landscape along with large rocks and flagstones. Portions of olla left exposed above ground should be glazed or treated to prevent evaporation.
To modernize these ancient irrigation systems, the jars may be recharged by a drip irrigation system, timed and sized to replace water lost from the ollas. Recharge of ollas may be done daily, or as frequently as allowed by water conservation ordinances.
The Olla, according to the Spanish English dictionary means “pot” and was used by Spanish speaking countries as a cooking pot. These clay pots were initially used by ancient Latin American cultures to cool water by evaporation. The techniques used to cool the water by evaporation have allowed for a great way to irrigate your garden and provide water directly to the roots of your plants. The pictures below show the use of the olla in a local garden.
Positioning the 1.5 gallon ollas in the raised (4′ x 8′) bed
Digging to submerge the ollas in the ground
The olla goes into the hole
Another hole for one of the ollas (notice the seed catalog in ‘Mr Seed addict’ pants pocket!)
Ollas are submerged. One tomato, two tomato …..
Filling up the ollas
A completed raised olla bed
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