More plants are drowned than dried out

When a balcony plant dies, the first thought is usually "I forgot to water it". Dig into the pot and the truth is often the opposite: the soil is wet, the roots have already rotted, they fall apart between your fingers, and there is a faint sour smell.

The reason is simple. Roots drink, but they also breathe. The pores in the soil are supposed to hold air, and every extra pour squeezes that air out. Roots sitting in oxygen-free water last only a few days, and the finest feeder roots go first. That is when the leaves start to droop, which looks exactly like thirst, so you water again. That last pour is what finishes the plant off.

So the real skill in watering is two decisions: how dry is dry enough to start, and how wet is wet enough to stop. Once those two numbers exist, a machine can hold them far more precisely than a person, and it never gets sentimental about it.

Why two numbers, not one

With a single number, say "water below 45%", the reading hovers right around that point forever. The valve opens, closes, opens again, and the soil never leaves that half-damp state that roots like least.

Pull the two numbers apart and the picture changes completely. The soil genuinely dries to 35% before any water flows, then it fills to 60% and stops, then nothing happens for days. That long swing between wet and dry is exactly when roots grow best. The technique is called hysteresis, and it is the heart of this whole setup.

What it actually did that week

The same week written out shows just how unhurried the rhythm is.

1. Mon morning

   Soil still damp, nothing happens

   Moisture reads 44%, well clear of 35%. The system takes a look every half hour and goes back to waiting. Nothing at all happens today.

2. Mon evening

   The first pour

   The reading falls to 35%, the valve opens, water reaches the pot. Two minutes later moisture is at 60% and the valve shuts. You were having dinner and never noticed.

3. Tue to Wed

   Slowly drunk down

   Moisture drops roughly ten points a day from 60%, faster in the heat. Through this stretch the soil moves from wet to dry, which is exactly when roots do their growing.

4. Thu afternoon

   The second pour

   Back down to 35%, so another two minutes of water, stopping at 60% again. This time a push notification arrives: 35% before, 61% after, one line and done.

5. Sun evening

   The week totted up

   Three pours in seven days, two minutes each. Never once above the 70% rot line, never once below 25%. You did not pick up a watering can all week.

Four things it takes care of

Before and after

What you need on hand

Home Assistant calls every device in the house an entity. Brand and model do not matter; what matters is the category it falls into. These are the ones this setup uses.

How the whole thing works

There are only three parts: one measures, one decides, one lets the water out.

Use a ready-made decision maker

The hub ships with 22 tested automation blueprints. Think of a blueprint as a fill-in-the-blank form: the boxes are already drawn, you only supply the contents. This setup needs exactly one of them, called greenhouse, which exists precisely to handle a pair of numbers.

Fill in those five boxes and both the starting and the stopping are handled. You do not write two separate rules, and you never have to work out what to do about a valve that keeps flicking on and off.

Different plants, very different numbers

The 35 and 60 above suit ordinary leafy houseplants. If that is not what is on your balcony, swap the whole pair — copying these across can actively hurt.

Two optional extras

One blueprint covers the core. These two are additions — take whichever one you actually need.

Two modes to switch between

You do not have to set this up yourself

None of the above needs clicking through box by box. The WOOWTECH smart hub runs HA-MCP, so the AI can connect straight into your system, build the thing, and then go back and check for itself that it really runs.

Prompts you can copy straight out

Every block below can be copied whole, using the button on the right. Pick the one closest to your situation — you do not need all of them.

Set up automatic watering for the plant on my balcony.
Water once the soil dries to 35%, stop at 60%, and do not flick on and off.
Find the devices yourself, and tell me plainly if you cannot find them.

Set up automatic watering on my balcony using an upper and a lower threshold.
Water only once soil moisture falls to 35%, and stop the moment it is back to 60%.
Check the soil every half hour, that is often enough.
Hold off during the few hours when the sun is strongest, and top up once it eases.
Message me after every pour with the moisture reading before and after.
If it hits 35% three days running without a successful pour, tell me to go and check the tubing and the valve.
Once it is set up, test it yourself, make sure it genuinely works, then tell me which devices you used.

What I grow on the balcony is succulents and cacti, not ordinary leafy pots.
Change the thresholds to water at 15% and stop at 35%, much lower than usual, which is correct for them.
Keep each pour short as well, under a minute.
They barely drink in winter, so two or three weeks with no watering is normal and I do not want alerts about it.

On the balcony watering rule, move the start threshold from 35% up to 42%.
It has been hot and the soil dries much faster than it used to.
Leave everything else alone and just confirm when it is done.

The soil never dries out, so I suspect it is getting watered more than once a day.
Start by listing every rule in the house that has anything to do with watering, including the ones I threw together myself.
Mark any pair that does the same job, or whose conditions overlap enough to fire together.
Once you are sure it is a duplicate, keep one of them and just disable the rest instead of deleting anything.

Common questions