Brought to the Americas by early Spanish settlers, ollas are unglazed pottery, with a large body (up to 18″ circumference), leading to a narrow neck, with a flared opening. The olla is buried in the ground leaving only the flare exposed and then filled with water. The unglazed pottery allows the water to seep through watering the roots of those plants near the olla.
Ollas cannot water plants with woody roots, which means I’m using them only for annual plants at this point. The woody roots could break through the terra cotta, and ollas aren’t cheap! I paid $30 a piece for my two and the entire 8 foot by 12 foot bed will probably need eight ollas! Before tax, that’s $240 for the first round of ollas – assuming they perform well enough to use throughout the water wise bed. On the other hand, the ollas should last for years longer than a drip system – certainly they’ll take less maintenance!
If this proves worthwhile, we should find a local potter who can make them – shipping must be a large part of the cost. One author made his own, using two regular terra cotta pots of the same size with silicone glue to close the bottom hole of one, then glued the two pots together, top rim to top rim (also with silicone glue). He used the top pot’s drain hole as a filler – he also put a seashell or a flat rock over the hole to prevent evaporation, which I thought was a smart idea. The olla will lose water to evaporation from any part of it exposed to air. An improvement in design would be to glaze the top three inches exposed to the air. Or, simply turn a pot of any material – from terra cotta to plastic – over the top of the olla.
How close does the olla have to be to your plants to water them? That’s a tough question to answer. You have to know what kind of soil you have. Sandy soil allows most water to go straight down and the plants will have to be very close to the olla. Clay soil forces water to spread into a much wider plume and the plants can be spaced much further from the olla. Almost everybody has soil that has some clay and some sand making exact distance hard find with certainty. We are starting with basil, tomatoes and marigolds – the tomatoes are out almost a foot from the olla (given extra water until they are three feet tall). The marigolds are four inches from the olla and the basil between the two. Note, I started with plants next to the ollas, I have not yet tried to use them to start seeds. Seeding will require a little more experience with the olla before I want to try.
Each type of plant will have different distances based on their needs and on your soil. Remember, it is the soil’s moisture that determines whether or not you refill the olla; an empty olla doesn’t automatically assume dry soil. At this stage of olla use, you are blazing a new frontier! Keep data on your experience and share it! We all need to learn how to grow greener gardens with less water!
Grandson of a Great Plains farmer, David King is the Garden Master at the Learning Garden, on the campus of Venice High School. He shares his love of the land and music through teaching, writing and playing in a folk/country band. Contact: email@example.com