Quick Answer: VPD (Vapour Pressure Deficit) is the measure of how hard air is pulling moisture from your plant’s leaves. Target 0.4 to 0.8 kPa for seedlings, 0.8 to 1.2 kPa in veg, 1.0 to 1.5 kPa in early flower, and 1.2 to 1.6 kPa in late flower. Use leaf temperature, not air temperature, when […]
