January 31, 2015

1 - Ollas may be used very effectively for growing potted plants.

Yard and Garden January 31, 2015


Do you advise using ollas for irrigation with indoor plants? I have seen other devices for providing slow irrigation for potted plants and was wondering if ollas would work as well.


Ollas (pronounced oyas), unglazed clay pots filled with water and buried in soil to provide slowly available water to plants will work very well in container gardens and for growing potted plants.

My preference is to use smaller ollas with potted plants. One olla for a smaller pot, allowing plenty of soil for the roots of the plants, but with a central olla that will provide water for one or perhaps two plants. As the water slowly seeps through the unglazed clay, the water becomes available to the plant or plants. The plants surround the olla with their roots so that, in time, water goes directly from the olla to the roots without moistening much of the soil. Once the olla is "claimed" by the roots of one or a couple of plants, other plant roots are excluded, so if there is to be more than one plant in a pot, they must be planted at the same time to give them adequate access to the olla. An advantage of the way that plants "claim" the olla by totally encasing the olla with their roots is that very little water will be available to run out of the pot onto furniture or floors. This direct olla to roots water supply provides less chance for evaporation and therefore increased water use efficiency.

Because of this encasing of the olla with roots, the plants may need to be fertilized with a dilute houseplant fertilizer applied to the potting soil outside the olla. Some nutrients, especially phosphorous necessary for flowering plants, may not pass through the clay walls of the olla. Since most of the very small absorbing roots of the plants will be close to the olla, this diluted fertilizer solution may be poured down the outside of the olla as well as into the soil.

For larger pots and container gardens with multiple plants several small ollas within a single pot may do the best job of providing water for the various plants. This will reduce the problem of one or a few aggressive plants from claiming a single larger olla.

I have even seen a situation where an olla was wrapped with sphagnum moss. This moss was held to the olla with wire or plastic mesh and the roots of herb plants were put into the sphagnum moss. The olla may then be hung in a window or other sunny location providing clean herbs ready for the kitchen.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.


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