VPD Masterclass: The Secret Key to Maximum Yield
Why relative humidity alone is misleading and how mastering Vapor Pressure Deficit (VPD) unlocks your plants’ full genetic potential.
What is VPD and Why Does It Matter More Than Humidity?
Most growers focus solely on temperature and relative humidity (RH). However, your plants “feel” something else entirely: the air’s pulling power. **Vapor Pressure Deficit (VPD)** measures the difference between the moisture in the air and how much moisture the air can potentially hold when saturated.
Optimal VPD Phases for Cannabis
Depending on the life cycle of your homegrow, your plants require different VPD ranges to thrive without stress:
- Seedlings & Clones: 0.4 – 0.8 kPa (High humidity needed for fragile roots)
- Vegetative Stage: 0.8 – 1.2 kPa (Balanced transpiration for robust growth)
- Flowering Stage: 1.2 – 1.6 kPa (Higher pressure to prevent mold and increase resin)
Vivosun Smart Grow Tip: Automation is King
If you are using the Vivosun SGS (Smart Grow System), you no longer need to calculate VPD manually. The Grow Hub controller monitors temperature and humidity simultaneously and adjusts your exhaust fans in real-time to keep your environment in the “Sweet Spot.”
This automation prevents growth stalls caused by dry air and protects your harvest during late bloom by aggressively countering high humidity that leads to bud rot (Botrytis).
