Growlink Precision Irrigation Controller
Global Version, with the controller plus an ESM3 climate sensor and a Terralink substrate sensor. This is not a timer. It waters your plants based on what the root zone and the room are actually doing, so you can steer your crop instead of guessing.
From watering by the clock to watering by condition
A normal timer says “feed six times a day for 90 seconds.” It assumes every day is identical, that plant demand never changes, and that every pot dries at the same rate. None of those are true.
The Precision Irrigation Controller reads the moisture and salt levels at the roots, reads the climate driving water use, and lets you water in response to that data. That shift, from fixed feed times to genuine feedback, is the entire point of the product, and it is what makes deliberate crop steering possible.
| Crop steering | Deliberately pushing a plant toward leafy (vegetative) or flowering and fruiting (generative) growth by adjusting watering, feed strength, light and climate. |
|---|---|
| VWC | Volumetric Water Content, meaning how wet the medium is. This is your dryback signal. |
| EC | Electrical Conductivity, meaning how concentrated the nutrient salts are at the roots. Your early warning for salt build-up. |
| VPD | Vapour Pressure Deficit, meaning temperature and humidity combined, telling you how hard the plant is pushed to drink. |
| Dryback | The drop in moisture between waterings. The core lever growers steer with. |
What a dryback actually looks like
With a timer, this is all invisible. You set a clock and hope. With a sensor and controller, the root zone becomes a picture you can read at a glance. This is the data the whole product is built around.
The green saw-tooth shows watering then drying, repeating through the lights-on period, with one long slow dryback overnight. The second line shows EC stacking up as the medium dries, the warning sign of salt build-up that appears before any visible plant stress. Bigger drybacks and higher EC steer generative. Smaller drybacks and lower EC steer vegetative.
Vegetative vs generative steering
Crop steering comes down to pulling the same four levers in opposite directions. The controller is what lets you move between the two strategies deliberately and repeatably, rather than relying on pot-lifting, runoff checks and gut feel.
The diagram shows the direction of each lever, not fixed targets. Exact moisture, dryback size and EC depend on your cultivar, substrate and growth stage.
The controller is the brain, not the plumbing
The controller is the intelligence layer that sits on top of your irrigation hardware. It reads your sensors and opens your valves, but it only works as well as the system underneath it.
What you need alongside it
- A constant-pressure pump such as a DAB, where the valve opening drops pressure and the pump powers up to hold it
- Up to four 24V solenoid valves (FloraFlex nylon or RPE are compatible)
- A pressure-regulated feed line with consistent emitters and good filtration
- A stable reservoir or batch tank, and a controlled substrate (coco, rockwool, mapito)
- 2.4 GHz Wi-Fi or Ethernet, since the platform is cloud-forward and reliable connectivity matters
The controller will not fix a badly built irrigation system. Uneven dripper output, unstable pressure, poor filtration and blocked emitters will still wreck consistency. The controller will expose them, not solve them. Get the hardware right, then this turns your system from time-based to condition-based.
Buy sensors as you grow
You do not need four sensors on day one. One controller drives up to four substrate sensors and four climate sensors across four independent zones, so you start with one, learn your room, and add sensors only as you start automating more zones. No upgrade, no trade-in, just plug the next one in.
- The most representative plant. A typical plant in your main zone. This is your monitoring baseline, covering first dryback after lights-on, moisture drop per hour, EC through the day, and overnight dryback.
- The fast-drying edge. Plants near walls, doors or airflow dry back faster. This answers “why are my edges different?” and stops you watering the whole room to suit one area.
- A different cultivar. Strains drink at different rates. One sensor on cultivar A tells you nothing about cultivar B, so this lets you steer each on its own terms.
- Propagation or veg. Smaller pots and younger plants dry back completely differently. Added last for full coverage across all four zones.
How it compares
Most growers shopping at this level weigh Growlink against TrolMaster and AROYA. Here is the honest positioning. Growlink is the data-led option that does not force you onto a subscription.
| Growlink | TrolMaster Aqua-X | AROYA | |
|---|---|---|---|
| Best at | Cloud data, AI steering, sensor plus climate bundled | Local reliability, lighting and CO₂, no recurring cost | Large commercial, autonomous steering |
| Subscription | Free app covers most; Pro optional (about £0.55/day) | None, one-time hardware | Required, ongoing |
| Sensors | 4 valves plus 4 substrate plus 4 climate | Add-on water-content sensors | Premium sensor tech |
| Sweet spot | Serious craft to small commercial wanting data | Grower wanting proven local hardware | Bigger commercial at scale |
Who it is for, and who it is not
A strong fit if you…
- Run high-value crops in coco or rockwool drip
- Already have a pressure-regulated line and 24V solenoids
- Run multiple zones or different cultivars
- Want to push dryback and EC strategy precisely
- Are willing to read graphs and adjust
Probably not for you if you…
- Run a small hobby tent or hand-water pots
- Have uneven drippers or an unstable pump
- Expect it to increase yield by itself
- Do not want to engage with data
1. It controls watering and valves only. It does not dose nutrients, which is a separate layer. 2. It will not fix a badly built irrigation system. 3. One sensor reads one plant, so start on a representative spot and add sensors to cover zones.
Three parts, one feedback loop
| Part | Role | What it does |
|---|---|---|
| Precision Irrigation Controller | The brain | Runs irrigation events, reads sensors, applies the rules, drives the valves, handles app and remote access |
| Terralink substrate sensor | Root-zone feedback | Moisture (VWC) and salt (EC) inside the medium |
| ESM3 climate sensor | Environmental context | Temperature, humidity, VPD, light, and CO₂ on the CO₂ version |
One controller scales to four substrate sensors and four climate sensors across four independent zones. The free iOS and Android app lets you monitor and manage remotely. An optional Growlink Pro subscription adds deeper graphing, alerts and analytics.
The ESM3 climate sensor requires a Bluetooth-capable controller, as older units are not compatible, and should be placed within the canopy near the top of the plants so it reads the conditions your plants actually experience.
