I have an olla with my 1 yr old Pom tree. After planting it I kind of regretted not having at least one more. My tree is fine so far but I think that maintaining moisture around the tree evenly might be the issue.

Thanks NachtSprite. I'm convinced now that three trees competing for the same limited water resource wouldn't be a good idea and it may influence tree roots to grow unnaturally in one direction thereby compromising the ability for the tree to remain upright. Cheers.

What is an olla?

A big ceramic pot that sweats water.

An olla pot is an ancient form of drip irrigation. They are a litle pricey but work very well. Here in Texas I am able to water my plants at oot level without wasting the water to evaporation.

http://urbanhomesteadsupply.com/clay-pot-olla.html

You can make your own affordably by gorilla gluing two terracota pots together (don't forget to plug one of the holes).

An olla system will work for trees BUT you need more than one (at least two on opposite sides located outside the canopy) and it will only work well on sandy soil in the arid southwest.

Why?

You want to water trees down 3 feet to drive the salts down below the vast majority of the roots. Or you will eventually kill the tree and poison the ground with salt. I doubt an olla can reach that depth unless the soil is very sandy. If it is the wet spot will be very small in diameter (the water won't spread out on the way down).

On shrubs, your target depth is 2 feet. Since the olla is mostly buried it already is around the first foot of depth so a somewhat loamier soil can exist and still likely reach that depth.

The other problem with two spots in the roots of the tree will only exist in the area(s) where there is water. No water, no roots. That makes them very susceptible to winds toppling, low nutrient uptake and drought.

In other parts of the nation where rainfall is plentiful at least some time of the year and the soil is therefor acidic ollas could work to get anything through the drought areas without causing long-term salt buildup past the next big rain. After all, 70% of tree roots are in the first foot of soil depth.

Ollas are covered/screened to prevent mosquito habitat or BTI added.

Here is a link that might be useful: ollas

Thank you for the information. I have not used one of these. I have seen a neighbor make something like this from old plastic gallon jugs. She planted a number of smaller crepe myrtles and turks cap. The jugs of water kept the plants going that first year.

One reason the ollas are not recommended for use with trees is that the roots may eventually break the pot. I have started some fruit trees with ollas because I like the constant source of water but, you do want to encourage the root growth to be more expansive. Also, when used in the vegetable garden I surface water very little. Trees will usually need a pretty deep soaking occasionally along with the olla.