By Mary Kathryn Dunston
Olla irrigation, an ancient technique, heralds from China and South America. And it’s starting to return to modern times.
The joys of gardening are what bring us back to the toils of weeding and insect bites, dirty nails and waiting. The anticipation in winter of planning our crops and the double anticipation of spring while patiently watching for that unfurling tip of a growing asparagus frond or the pea green tip of that legume to emerge anchors that joy that grows in gardeners.
And then there’s watering, that necessary aspect of growing a garden that we design our day around. We ponder, “Should I water in the morning before work, or in the evening when I’m tired?” “It’s supposed to rain today, but what if it doesn’t?” Or, “I better water before the sun gets too hot.” Rainfall, no rainfall, irrigation investment, time investment, the cost of city water or the level of well water all play a part in how often or how long one can water. There must be an easier way to do this. There is. There is an easy and “new” way of watering that is more than 2,000 years old, clay pot irrigation.
More than 2,000 years ago, when Google didn’t have the word “hose” in its data bank, ancient people from China to South America were burying porous clay pots in their gardens and next to their saplings. The bulbous clay pot, known as an olla (oi-yǔ), would have a neck on it which would be visible just above ground level. The opening at the neck allowed the gardener to add water into the pot, or olla, as the olla emptied. This was ingenious because the water in olla irrigation was pulled out by the thirsty roots of the surrounding plants. Soil moisture tension was at work—not an ancient word, but that is what was happening none-the-less. Every plant got water as it needed it. No water was wasted and no plant was over- or under-watered. As you have no doubt figured out, ollas are still used around the world today, but in our country, the concept is just seeping out.
People are learning that ollas are easy to install. Dig a hole and put the olla in it. Backfill. Okay, that was easy. Adding water to olla irrigation is quick. Lift the lid off, put your hose in, wait 30 seconds or so, put the lid back on. If you get bored in those 30 seconds, bend over and pull what few weeds are around the olla. There won’t be many since olla irrigation keeps the water below the soil surface, discouraging weed growth. Planting around the olla is just like planting anywhere. Ollas work in ground, in raised beds and containers. People are using them in everything from a water trough to a truck bed. How far out the water seeps from olla irrigation depends on the olla size and soil type. A larger olla, say two gallons, will water an 18-inch radius in most garden soils. That’s a three-foot circle watered with one olla, about the area of a 4×4 raised bed. It will need filling every three to five days. Fill the olla on Saturday and then check again on Tuesday. Olla irrigation can save up to 70% in water use, due to the low evaporation rate and the zero runoff rate. Using water so wisely saves you money and puts less stress on a water source.
Because ollas are porous, they work in two directions. When water is on the OUTSIDE of an olla, as when it rains and rains and rains, by gravity, some water will seep back INTO the olla. This decreases the splitting of tomatoes, melons, etc. The olla needs to be partially empty for this to work best since the excess ground water needs someplace to go. It is nice to know, however, that the time invested in setting up this ancient watering system is never wasted, rain or no rain. As Randall Isherwood, owner of Garden Outposts Nursery in Columbia, South Carolina, put it, “Last year we had a deluge of rain every week, tomatoes were splitting all over the state. My tomato plants that I had installed with olla irrigation averted this splitting issue 100% of the time, in all types of locations in ground, containers and raised beds.” Even if 100% isn’t a guaranteed success rate, Mr. Isherwood is not far from the norm. In addition, the root base of plants around olla irrigation is larger and happier since they have water consistently, and can be fertilized, by adding a liquid fertilizer in the olla. Finally, in our modern times, we have some added bonuses those ancients couldn’t have dreamed about. Olla irrigation does not need electricity and has no plastic residue. They are environmentally safe across the board.
Clay pots (ollas) have been used to irrigate plants for thousands of years. A two-gallon sized olla, for example, will water a three-foot circle area (above) around the pot. Another cool fact – if it rains a lot, the olla will absorb some of the excess water – a double bonus!
So, next winter, when you’re huddled next to the fire and pouring over your spring catalogs from top seed companies, think clay pot irrigation, the most efficient watering system known.
Have you tried olla irrigation? How did it work for you?
Mary Kathryn Dunston is an avid gardener who teaches about Clay Pot Irrigation for Dripping Springs OLLAS.
Also, find her on Facebook at Dripping Springs OLLAS.
Originally published in Countryside November/December 2014 and regularly vetted for accuracy.