Best Olla Watering Pots

What an olla actually is

An unglazed clay vessel, buried to its neck in a bed or a large container, filled with water and capped. The clay is porous. Water moves through the wall toward drier soil, and it moves faster when the soil is dry and slower when it is wet. The Olla Company puts it as plainly as anyone: when the soil is moist, the flow pauses on its own. Roots grow toward the pot and take water from its surface.

That makes an olla a demand-driven device, like a ceramic cone and unlike a timer. It delivers less on a cool wet week and more on a hot dry one, without a valve or a schedule. It is also, in effect, a very large terracotta spike with the bottle built in - the same porous-clay throttling that makes spikes better behaved than glass globes, scaled up to a garden bed.

How we ranked them

Published capacity first. An olla is a reservoir, and a reservoir product that does not print its volume cannot be compared with one that does. Four of the five here publish a figure. One does not, and it finishes last for that reason alone.

Published reach second. This is the number a bed gardener actually needs: how far from the pot does the moisture travel, and therefore how many pots does a bed need? Two makers here publish it as a diameter. It depends on soil, and every maker should say so, but a published figure beats a guess.

Honesty of the duration claim third. We ran every published capacity through our arithmetic. The results are in the table, and they separate the makers more sharply than anything else on the page.

Setup guidance fourth. An olla does nothing until roots reach it. The maker that says so on the box scores higher than the ones that do not.

The same 700 ml, sold two different ways

Look at rows two and four. Back to the Roots and DoubleFill both publish 700 ml, both publish an 18-inch reach, and both say the pot serves two large plants. Back to the Roots calls that a week and, elsewhere on the same listing, a long weekend. DoubleFill calls it up to three weeks. The clay did not change and the volume did not change. Only the sentence did.

Here is the arithmetic, on the only case our published bands actually cover. A single tropical plant in an 8-inch container takes about 800 ml per thorough watering in our pot table, and Virginia Cooperative Extension publishes the cadence as once or twice a week. Seven hundred milliliters is 0.9 of a watering, which is 3 to 6 days. In a 12-inch container at 2,800 ml per watering it is a quarter of a watering - under two days. Three weeks from 700 ml would need a plant drawing about 33 ml a day, which is a small succulent, not two large plants.

We score honesty of claims because it predicts something. A maker that under-promises on the one number you can check is likelier to be right about the numbers you cannot. That is why GrowOya, whose five-to-seven-day claim sits inside our range for a 3 liter pot in a large container, is first, and why the three-week claim is the reason DoubleFill is fourth despite being the best value per pot on the page.

Why we do not compute a bed interval

Everywhere on this site the refill interval is reservoir capacity divided by one thorough watering, multiplied by a published cadence - the method is here. Those cadence bands are for container houseplants indoors. A raised bed of tomatoes in July draws several times that and varies with the weather from one day to the next, so applying the band to a bed would produce a flattering number and mislead you. We say the same about every product on our vegetable garden page, and it applies here with full force.

The container columns are the honest version of the vacation question. An olla in a big patio pot is a sound idea and the 3 liter class is the one that makes it work; a 700 ml olla in a big pot is a long weekend, and its makers should say so.

The two-week rule that decides whether it works at all

GrowOya publishes the instruction the whole category depends on: surface-water normally for the first couple of weeks, then let the pot take over. An olla delivers water to the roots that have reached its wall. A newly planted bed has no roots at the wall, and a full olla in that bed does very little while the seedlings dry out around it. Buyers skip this step, blame the pot, and return it.

The corollary is that an olla is a season-long installation, not a night-before-the-trip fix. Bury it at planting time, water conventionally until the bed is established, and by the time you travel the roots are where the water is. If the trip is next week and the bed is already planted, a terracotta spike with a bottle delivers to the surface roots you already have.

How many, and how far apart

Buy by the published reach and halve it for spacing. Bio Green publishes 23.6 inches of irrigation diameter for its small olla, Back to the Roots and DoubleFill publish 18 inches for a 700 ml pot, and The Olla Company publishes up to three feet for its large. Reach is a property of the soil as much as the pot - water moves further through a loose, organic mix than through compacted clay - so treat every figure as a sunny-day optimum and plant within it, not at its edge.

A four-foot by eight-foot bed at an 18-inch reach is roughly six small ollas or two to three large ones. At that count the per-pot price matters, which is the case for the multipack - and the case for ignoring its three-week claim while you buy it.

Where an olla fits against everything else on this site

An olla is for beds and large containers, outdoors, over a season. It is the wrong tool for a houseplant: too large for most pots, and the 1 liter smalls are the only sizes that fit a big indoor container. For a shelf of houseplants, a wine-bottle stake is the same clay mechanism at pot scale. For a sub-irrigated planter with the reservoir built in, the EarthBox class of box publishes its numbers and needs no burying. The olla sits between them: a reservoir you add to soil you already have.

Maintenance, and the part every maker mentions quietly

Porous clay clogs. Minerals from hard water and fine soil particles build up in the pores over a season and the flow drops. GrowOya publishes the fix - a wire brush and a vinegar solution - and it applies to every pot on this page. Lift them at the end of the season, scrub, dry and store; an unglazed clay vessel left full of water through a hard freeze is a risk we would not take with any of them.

Keep the cap on. An open neck loses water to the air, and Back to the Roots is right to make a point of its stopper. If a maker sells the pot without a lid, a saucer or a flat stone does the job.

The honest cons on every pick

GrowOya Oya medium. Expensive per pot next to the generic packs. Needs the two-week establishment period like everything else. No published reach figure, which is the one number it is missing.

Back to the Roots. Seven hundred milliliters is a small reservoir for the two large plants it is sold as serving, and a week is above our range on any single big container. Buy it as a long weekend and it is honest.

Bio Green Hydro MAX S. The reach figure is generous for 1.1 liters. Pricier per liter than the multipacks. The larger sizes in the same range are the ones that match the published reach.

DoubleFill 4 pack. The three-week claim is the least defensible figure on this page. Quality varies in this bracket and a dense-fired olla releases very little. No published reach.

The Olla Company large. No published capacity, which for a reservoir is the number that decides duration. The most expensive pot here. The mechanism description is the best in the category, and we wish it came with a volume.

The verdict

Ollas are the best-behaved outdoor watering device on this site, because the clay responds to the soil instead of to a clock. Buy one with a published capacity, size it to the bed rather than to the claim, bury it at planting, and give the roots two weeks to find it. Do all four and the method works exactly as it has for a very long time. Skip any of them and it is a clay pot in the ground.