If you water a garden in summer, you already know the problem: the sprinkler wets the surface and the air, the weeds drink first, and on free-draining sandy ground the water is gone before the roots see it. This page answers a specific question — how to water at root depth with no timer, no drip line, and no electricity, and refill on a schedule measured in days, not evenings.
The problem, plainly
Surface watering loses most of its water to evaporation, feeds weeds, and trains roots to stay shallow where the soil dries fastest. Drip systems fix the delivery but add plumbing, pressure, and parts that clog and fail. The buried-pot method sidesteps all of it. It is one of the oldest water techniques in the world — the agricultural records of ancient China include it — and the principle has never needed improving, only remembering.
What actually works
An olla is an unglazed clay pot buried up to its neck, filled once, and capped. Water seeps through the porous clay wall by capillary action — drawn out only as the surrounding soil dries. Wet soil holds the water back; dry soil pulls it out. The pot self-regulates: no timer, no valve, no electricity. Delivery is deep, 15–25 cm down at root depth, so the surface stays dry — fewer weeds, far less evaporation — and the release is slow, metered over days rather than minutes, so the soil never floods and never starves. Roots grow to the pot, and the water goes to the roots. The rule of thumb is one litre of pot per plant; a 5–10 litre olla covers a small bed. The pot must be unglazed terracotta — glaze seals the pores and stops the whole mechanism. The classic DIY version is two flower pots joined mouth-to-mouth with the bottom hole plugged.
How to run it
- Choose the pot. Unglazed terracotta, about one litre per plant or 5–10 litres for a bed. Glazed pots don't work — the wall is the mechanism.
- Install before the dry season begins, while the soil is still soft enough to dig, so roots meet water from the start.
- Bury it in the root zone at the dripline of the plant, not at the stem. On sandy ground, where beds dry faster, sink the pot a little deeper.
- Seat the pot firmly so no air gap forms along the wall — an air gap kills the capillary contact — then backfill and tamp gently.
- Fill to the brim and cap it with the saucer or a stone. The cap is what stops evaporation.
- Refill when the level drops — roughly every 3–7 days in summer. That is the whole schedule.
Where it fails
- A sealed pot. Glaze, paint, or a plastic liner blocks the pores; the water stays in the pot and the roots stay thirsty.
- An air gap. If the wall isn't seated against the soil, water seeps into the gap instead of the root zone. Tamp the backfill.
- The stem, not the dripline. Roots drink at the canopy edge; a pot at the stem waters nothing that needs it.
- Installing mid-drought. The ground is hard and the plants are already stressed; timing is part of the method, not a detail.
- Wrong size. One litre roughly waters one plant; an under-sized olla empties in a day, an over-sized one wastes clay.
- Ignoring the sandy-soil pairing. On free-draining ground, pair the olla with a cover-crop mulch to slow surface drying further — water at the root, mulch on top.
The short version
Bury an unglazed clay pot to its neck at the dripline, before the dry season; seat it so no air gap forms; fill it, cap it, and let the soil pull what it needs; refill every 3–7 days in summer. Water is released 15–25 cm down at root depth, the surface stays dry, and the weeds and the evaporation get almost nothing. The oldest honest way to water, and still no moving parts.
From the Olla Irrigation Guide
Olla Irrigation Guide — PDF ($7) →
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