Vpd Vapor Pressure Deficit

Vapor Pressure Deficit (VPD) is a measurement of the difference between the amount of moisture in the air and the maximum amount the air can hold at a given temperature. In cannabis cultivation, VPD is expressed in kilopascals (kPa) and directly influences transpiration rates, nutrient uptake, and plant growth dynamics. Most cannabis growing environments target VPD ranges between 0.8–1.5 kPa during vegetative growth and 1.0–1.6 kPa during flowering, though optimal ranges vary by growth stage and cultivar phenotype. Breeders and cultivators monitor VPD because plants adapted to specific regional climates often exhibit measurable differences in leaf morphology, stomatal density, and water-use efficiency under varying atmospheric conditions. Understanding VPD helps predict how a strain's genetic expression may shift across different cultivation environments.

Breeders working with regional landraces or developing cultivars for specific climates often document how genetic lineages respond to different VPD conditions. Selecting parent plants with consistent performance across varying humidity and temperature regimes can produce offspring better suited to diverse growing environments.