Olla

Anollais aceramicjar, oftenunglazed, used for cookingstewsorsoups, for the storage of water or dry foods, or for other purposes like theirrigationofolivetrees.Ollashave short wide necks and wider bellies, resemblingbeanpotsorSouth Asianmatki.
The Latin wordollaoraulla(alsoaula) meant a very similar type of pot inAncient Roman pottery, used for cooking and storage as well as afunerary urnto hold the ashes fromcremationof bodies.  Later, inCelticGaul, the olla became a symbol of the godSucellus, who reigned over agriculture.
In Spain, the popular disholla podrida(literally “rotten pot”), cooked in anolla, dates back to theMiddle Ages.
In certain areas of thePyreneesinCataloniaa type ofolla, known locally astupí, is used as container for the preparation oftupí, a certain type of cheese.
The Spanish settlers may have introduced theollatoNative Americantribes which they reproduced for sale to colonists, but they had their own traditional pots attributed to their respective tribes. Catawba potters, native to the southeast, used unglazed pottery.
Among SouthwesternNative Americantribes,ollasused for storing water often were made with narrow necks to prevent evaporation in the desert heat. Theollais used by theKwaaymiipeople, among many others, for cooking, storing water, serving meals and even nursing infants.
The termollais also applied to regional basketry shaped with bulbous bodies and narrow necks.Ollabaskets are commonly used by theWestern Apache,Shoshone, andYavapai.
Because water seeps through the walls of an unglazed olla by usingsoil-moisturetension, one can use ollas to irrigate plants. The olla is buried in the ground, with the neck of the olla extending above the soil. The olla is filled with water, and plants such as tomatoes, melons, corn, beans, carrots, etc are planted around the olla. Or, an olla can be put near a new sapling, or bush to get it through its first year.  After that, given enough annual rain, the olla near the tree or bush can be lifted out of the ground and used somewhere else.
Olla irrigation works like this:
How far out the water is pulled depends on the size of the olla and the quality of the soil.  Dense soil (clay) does not water out as far as good soil.  Large ollas, with a capacity of (say) 11 liters, will water longer than a smaller 1 liter olla, for example. Olla, or clay pot, irrigation is considered the most efficient watering system by many, since the plants are never over- or under-watered, saving from 50% to 70% in water, according toFarmer's Almanac.Watering below the soil level allows the plant roots to get what water they need, and therefore to grow stronger roots. As Geoff Lawton says, clay pots can make your garden drought-proof.Little water is lost to evaporation or run-off.
Spanishsettlers introduced this irrigation technique to the Americas incolonialtimes. Agriculture and gardening specialists are teaching it, and olla use is making a comeback inNew Mexicoand the American West. The state's master gardening program is spreading the word. It can be effective for homeowners to use in the desert climate.It has also been put to use by the Global Buckets project.
As a modern gardening tool, ollas are generally made from terracotta plant pots.There are various methods to create them, but one of the easiest is to fill the bottom opening in an unglazed terracotta pot, bury it in the ground, and keep it topped up with water. Plants need to be within roots'-reach of the olla to make use of the water reservoir.
In their September 2013 newsletterEcology Actiondescribes using five 5-gallon ollas for a 100-square-foot garden plot. The test plot used 1.25 gallons per olla every four days. The ollas are fitted with caps that reduce evaporation and collect rain.
Theollais also useful for keeping water cool. When an unglazedollais filled with water, the water permeates the clay walls of the vessel, causing theollato “sweat”. The evaporation of the sweat cools theollaand its contents. In the early 20th century, many ranches in the American Southwest used the practice of hanging anollafrom a rope on theverandahin a shady, breezy spot. Several hours after theollawas hung, it was cooled enough by evaporation to keep butter and milk safely cold.
In addition to utilitarian purposes,ollasare also produced by Native American and Mexican potters asartistic works. Theseollasmay be highly decorated and/or formed.