Vpd Vapor Pressure Deficit

Vapor Pressure Deficit (VPD) is not a terpene, but rather an environmental measurement critical to cannabis cultivation science. VPD quantifies the difference between the amount of moisture the air can hold versus what it actually contains, expressed in kilopascals (kPa). Breeders and cultivators monitor VPD because it directly influences transpiration rates, nutrient uptake, and terpene expression in developing flowers. Cannabis plants typically thrive within VPD ranges of 0.8–1.5 kPa during vegetative growth and 0.4–1.0 kPa during flowering, though specific lineages may show variable responses. Understanding VPD helps explain why environmental conditions—rather than genetics alone—significantly shape final aromatic and cannabinoid profiles across phenotypes.

Breeders use VPD data to standardize growing conditions when phenotype-hunting or stabilizing lines, ensuring that observed trait expression reflects genetics rather than environmental stress. Strain families developed in specific climates often show measurable differences in vigor and terpene output when grown under non-optimal VPD, making this metric essential for reproducible breeding programs.