How much water does a planter lose before a plant drinks any?

We weighed one planter for two days on a kitchen scale. The first day it was open. The second day it had a mock-up of our planned lid. The lid cut evaporation by about 70%.

Published October 12, 2026

Concluded experiment

How much water does a planter lose to the air on its own, and is a lid over it worth having?

Started

July 28, 2026

Ended

July 30, 2026

Hypothesis

A lid should slow evaporation enough that a reservoir lasts a month between refills, not a week or two.

What we measure

The weight of one sealed acrylic planter of LECA and water, with no plant in it, on a kitchen scale reading in 1 g steps — every few hours for about a day per run, open for the first and under a foam-board mock-up of the lid for the second.

Conditions

Indoors, about 25 °C by day (air conditioning on) and 22 °C at night, humidity around 65%

Result

Hypothesis held

The lid cut evaporation by about 69%, to roughly 12 g a day per planter — a six-planter wall gives up about half a liter a week, well inside a monthly refill.

A clear planter filled with LECA clay pebbles, covered with a white foam-board lid that has a long slot down the middle, next to a kitchen scale — Day two: the same planter under a foam-board mock-up of the lid. Only the slot, where the plants would go, is open to the air.

How much water the wall has to carry

Every Meadori planter holds a shallow pool of water under a bed of LECA, the round clay pebbles in the photos. Some of that water goes to the plants. The rest evaporates into the room from the wet clay at the top.

That second share decides how big the reservoir has to be, and the reservoir is the heaviest thing on the wall: water weighs a kilogram a liter. If a planter gave up water quickly, we would have to carry a lot more of it to keep the refill interval sensible — and a frame heavy enough to hold that much water is a different product from the one we are building.

So this was a go or no-go on the recirculating design. Leave the plants out, measure the evaporation on its own, and find out whether a reservoir we can hide in a picture frame is enough. Two runs, and they only make sense together: the open run is the baseline, with the whole top of the planter exposed, and the lidded run shows what the planned lid saves.

One planter, two days, a kitchen scale

We took a transparent acrylic test planter the size of one Meadori planter, sealed it with silicone so it couldn’t leak, filled it with LECA, and topped it up with water almost to the brim. It sat indoors, at about 25 °C during the day with the air conditioning on and 22 °C at night, with humidity around 65%.

On day one the top was open. On day two we taped on a foam-board mock-up of the lid we plan to use, with a slot down the middle where the plants would sit. Everything else stayed the same: the same planter, the same table, the same scale, the same room.

The open planter full of LECA sitting across a kitchen scale that reads 1149 grams — Run 1, first reading: 1,149 g with the top open.

Between the runs we topped the planter back up, and the foam lid and tape added a little weight, so run 2 starts heavier than run 1 ended. Only the change in weight matters, so the starting weights don’t need to match.

Side view of the planter with the foam lid taped down along its edges, LECA visible through the clear wall — Run 2: the foam lid, taped down along every edge so the only opening is the slot.

The lid kept about two-thirds of the water in

Open: 40.5g/day
Lidded: 12.4g/day
Saved by the lid: 69%

Water lost since the first reading

Open
Lidded
Overnight, no readings

Both lines are close to straight. The planter lost water at a steady pace through the afternoon, the evening and the night, with no sudden jumps. That steadiness is a good sign the readings are real and not scale noise.

The lid made the difference at every hour. Open, the planter lost about 1.8 g an hour in the afternoon and evening, and about 1.6 g overnight. Lidded, it lost about 0.6 g an hour in the afternoon and about 0.4 g overnight.

Stretch	Open	Lidded
Afternoon and evening	1.8 g/h	0.6 g/h
Overnight	1.6 g/h	0.4 g/h
Next morning	1.5 g/h	0.6 g/h
Whole run	40.5 g/day	12.4 g/day

Why the lid works

Water evaporates from the wet surface of the LECA into the moving air of the room. The lid covers almost all of that surface and leaves only the plant slot open, and the air trapped underneath stays humid — so less water leaves.

Two runs, read with care

One run each. We measured each setup once, for about a day. The result is a clear direction, not a precise constant.
Back-to-back days, not side by side. The runs were on consecutive days in the same room, under the same conditions: about 25 °C by day with the air conditioning on, 22 °C at night, humidity around 65%. A side-by-side run would rule out what small day-to-day differences remain.
No plants. This is evaporation only. Plants drink and breathe out water through their leaves, and on a living wall that’s the bigger share. We’ll measure it on a planted wall.
Water almost to the top. In use, the water sits lower, under more dry LECA. A lower water line would likely lose less, so these numbers are on the high side.

The lid stays in the design

A lid over each planter keeps roughly two-thirds of the evaporation in. It also hides the clay and leaves only the plants on show, which is what living art should look like.

The test planter is the size of one Meadori planter. If each planter on a six-planter wall like Sam lost 12 g a day, the wall would give up about 75 g a day to evaporation, or about half a liter a week. That’s small next to Sam’s planned 4.5 L reservoir, so it leaves plenty for the plants.

Next, we want the whole picture: how much water a planted wall uses in a day, plants included. Sam is the place to measure it once its water loop is running.