VPD Explained for Complete Beginners

VPD stands for Vapor Pressure Deficit. Think of it as the air’s drying power.

If the air is too dry (high VPD), plants sweat too much and slam their stomata to save water. Growth stops. If the air is too humid (low VPD), they barely sweat. No water movement means no calcium uptake.

You want the Goldilocks zone. For early veg, aim around 0.8 kPa. For flower, push 1.2–1.4 kPa.