Last spring I got my hands on a couple of ollas, and was eager to see how they would perform as the sole water source for a garden bed of tomatoes, peppers and flowers (see my post from last April, here). The concept behind using ollas--vase shaped, unglazed terra cotta vessels with lids, is to bury them in a garden bed, fill them with water periodically, and plant around them. Water slowly wicks into the soil surrounding the unglazed ollas, where plant roots colonize.
So...were they a success? Did they save water? Were the plants happy? Yes! On all counts, I'd say they did as well as drip irrigation. Here are the things I learned:
- On average, the ollas needed filling every 6-7 days. They wicked water consistently over the season. I expected them to need more filling during hotter months and heat waves, but it wasn't so.
- Each olla wicked water at a slightly different pace. One of mine always wicked one-third of its water very quickly after filling, then slowed to match the pace of the other.
- The soil surface stayed dry. Water wicked from the bulbous part of the olla, keeping the soil surface dry and weeds from germinating.
- The plants surrounding the ollas needed no additional water.
- Each olla held 2.5 gallons of water, so roughly 5 gallons per week supported 4 tomato plants, 4 peppers, and a couple of cosmos and echinacea.
In the fall, I decided to dig up the ollas and place them elsewhere. But as I dug around them, I found the soil there full of big earthworms, and the soil structure was incredible. A happy, healthy ecosystem had formed, and I just couldn't disturb that, so I opted to leave them and plant perennials around them. As warm weather returns, I'll begin filling them again. Now I can't wait to see how those plants thrive.
Ultimately, if you're a reasonably attentive gardener, willing to spend a few minutes per week with a hose and interested in saving water, this could be an option for you. I've seen automated filling systems, but I'm not inclined to go that far. If you garden in a place with cold winters, you would need to pull out the ollas before a hard freeze.
Note: I know I know, I should have pictures of happy healthy plants growing around buried ollas. I wasn't that organized.