Dial in your environment.
Air temperature. Humidity. Leaf temperature. See how they work together, right here.
Measure the leaves.
Read the room.
Enter measured air temperature and RH at canopy height, plus measured leaf temperature. Leaf temperature is independent of air temperature; re-measure it when conditions change.
The starting values are our week-four flower example. Use the target in your current grow chart for your crop stage.
Feed charts & grow documents ↗0.16 kPa above your selected target.
- Air VPD
- 1.49 kPa
- Dew point
- 66.7°F
64.2% RH for 1.10 kPa
If air stays at 82.0°F and leaves at 80.0°F, 64.2% RH gives your selected target. This is a calculation, not an automatic climate setting.
Make small changes, let the room settle, then re-measure air, humidity and leaves.
If VPD is too high
Test higher RH or a lower temperature within your stage’s guidance. After adjusting, check whether pots need less frequent irrigation.
If VPD is too low
Test lower RH or more warmth within your stage’s guidance. Check whether pots dry faster, and watch nighttime humidity separately.
Keep the whole crop in view
VPD alone does not tell you to change the nutrient recipe. Review irrigation, feed and runoff alongside the environment.
Read the VPD correction guide ↗Ask a grower.
Feed questions. Order questions. We’re here for both.