Humidity Vapor Pressure Deficit

Vapor Pressure Deficit (VPD) is not itself a terpene, but rather an environmental measurement that significantly influences terpene production and expression in cannabis plants. VPD describes the difference between the amount of moisture the air can hold at a given temperature versus the moisture it actually contains, measured in kilopascals (kPa). In cannabis cultivation, VPD directly affects how plants transpire and allocate metabolic resources, which in turn impacts secondary metabolite synthesis including terpene accumulation. Breeders and cultivators working with specific strain genetics often correlate optimal VPD ranges (typically 0.8–1.2 kPa during flowering) with enhanced aromatic profiles. Understanding VPD is essential for phenotype expression, as the same genetic material can produce markedly different terpene ratios under varying humidity and temperature conditions.

Breeders track VPD conditions during strain evaluation and preservation to ensure consistent terpene expression across generations and growing environments. Controlled VPD documentation helps breeders identify which genetic lines produce stable aromatic signatures under standardized conditions, supporting seed-line stability and lineage record accuracy.