Friday, July 19, 2013

How to make ollas for your garden or landscaping

Your first question is undoubtedly, "What the heck is an olla?"  It's Spanish for a particular type of pot, but I'm using it in an irrigation context.  It's an unglazed ceramic jar used to deliver water to plants in a very efficient manner. 

Here is a dry one freshly exhumed, because I was re-planting this container. 
You simply take two cheap same-sized flowerpots, place them top-to-top, and seal the seam with silicone caulk.  Then also plug the bottom pot's drainage hole with silicone, leaving just the top hole open.  Then you bury them in the soil up to the level of the open hole.  Whittle down an old wine cork or something to stick in that hole so dirt and mosquitoes won't get into it. 

Then you keep it full of water as a means of passive irrigation. 
Here's this one removed from the soil and filled for a photo op.  The water will seep out slowly through the porous clay. 

You can also purchase commercially-produced ollas, and to my surprise they're even being carried by big-box hardware stores now, but they're far cheaper to make than buy.  You can make one for about one third the cost of retail. 
It's a simple idea, but it really works, as this photo suggests:
Sorry about the poor depth of field on this photo, but this is an olla hole where one was removed from the soil.  You can see that the plant roots had preferentially wrapped themselves around the olla so that they could suck water through the clay, much the same way as tree roots will penetrate and exploit a seeping water or sewer line. 

The only limitation I've found is that you can't make them too large.  The larger the flower pot, the thicker the clay walls.  Large pot walls are still porous, but the water doesn't seep out as efficiently. 
Ollas can be very useful in climates like ours, especially when we go for prolonged periods with hot weather and no rain, such as we just experienced. 
Once again this year, we are sucking wind on rainfall.  That tropical wave we had a few days ago furnished the first significant precipitation since freakin' April, and it's now mid-July. 

Screengrab of YTD from Wunderground station MD6282, which is located here in Centerpointe. 
Ollas are particularly useful when embedded in raised planting beds and large containers, which tend to dry out much faster than soils on grade.  Container gardens in greater Houston will often completely dry out in less than 24 hours, as in, kill-your-plants dry out.  If you don't water containers daily during the summer here, you'll usually lose your plants.  I have found that keeping an olla filled and installed next to sensitive plants will buy me some leeway on the timing of my regular watering because the seeping tides the plants over until I can get to this task. 

If you have small children, making ollas can be a good family project, as many kids love to get involved with this kind of thing.  Now that it's summer and school is out, a few of the neighborhood kids have become fond of asking me, "Do you have any work that I could help with today?" (seriously!) because they see me working on my landscaping frequently and they like to get involved.  One of these days I'm going to remember to stop by the hardware store and pick up another batch of clay pots so that we can collaborate on making some more of these. 

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