By Mary Kathryn Dunston – The joys of gardening are what bring us back to the toils of weeding and insect bites, dirty nails and waiting. The anticipation during winter of planning our crops and the double anticipation of that unfurling tip of an asparagus frond, or the emerging green tip of that legume, anchors the dormant joy that grows in gardeners every spring.
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!
Over 2,000 years ago when Google didn’t have the word “hose” in its data bank, ancient peoples 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), was designed with a neck on it. The bulbous part of the olla would be buried in the ground, and the neck would be visible, just above ground level. The opening at the neck allowed the gardener to add water into the olla as it emptied. And what emptied the olla was the dry soil in which the olla was buried. The dry soil slowly pulled the water through the olla wall. Soil moisture tension was at work — not an ancient word, but that is what was happening nonetheless.
Every plant got the water it needed by absorbing the water from the soil. And the soil got what it needed from the olla. No water was wasted and no plant was over or under watered. Ingenious! 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. And since good news travels fast, community gardeners, Master Gardeners, home and university gardeners are all sharing the news.
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 the olla 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 ollas keep the water below the soil surface, discouraging weed growth. Planting around the olla is just like planting anywhere. After burying the olla, put seeds or plants around the olla. Ollas work in ground gardens, in raised bed gardens, and in containers. People are using them in everything from a water trough to a truck bed.
How far out the water seeps from the olla depends on the olla size and soil type. A larger olla, say 2.9 gallons/11 liters, will water an 18-24 inch radius in most garden soils. That’s a 3 foot+ circle watered with one olla, about the area of a 4×4 raised bed. A medium olla, about one quart, is well placed in a container or in an in-ground garden, surrounded by short rooted plants, such as lettuce and radishes. The watering diameter for the one quart olla is about a 20 inch circle. Both sizes will need filling every three to seven days, depending on rainfall, soil type, and mulch. Fill the olla on Saturday and then check the water level again mid-week. The time you saved not hand watering can be spent, well, doing what ever you want! Ollas not only save time, they save water. Using an olla can save up to 70 percent in water use, due to the low evaporation rate and the zero run off rate. Using water so wisely saves you money and puts less stress on a water source. Not bad for a piece of organic clay.
But there’s more! Because ollas are porous, they work in two directions. When water is on the OUTSIDE of an olla, when it rains and rains and rains, some water will seep back INTO the olla due to gravity. 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 Ollas averted this splitting issue 100 percent of the time, in all types of locations in ground, containers, and raised beds.” Even if 100 percent isn’t a guaranteed success rate, Mr. Isherwood is not far off the norm, which is closer to 75 percent. In addition, the root base of plants grown around ollas is larger and happier, since consistent water grows a larger root, which grows a better (happier) plant.
If you garden in a cold area, look for an olla with a thicker wall to allow for wintering over in the ground. Be sure to have your ollas water-free a week or so before the first frost if you chose to leave them in the ground. And for good measure, cover the exposed neck and lid with some mulch. Finally, in our modern times, we have some added bonuses those ancients couldn’t have dreamed about. Ollas do not need electricity and have no plastic residue. They are environmentally safe, and in this day and time, that is important.
So, this winter, when you’re huddled next to the fire and pouring over your spring seed catalogs, think clay pot irrigation, the most efficient watering system known. Google olla to learn more or to find them at your local nursery.
Mary Kathryn Dunston is an avid gardener who teaches about olla irrigation and has over 30 ollas in her yard. She is the owner of Dripping Springs Ollas.
Originally published in Countryside November/December 2014 and regularly vetted for accuracy.