Less water, same buds: moderate drought as a water-saving strategy for indoor cannabis.

Crispim Massuela D.; Munz S.; Hartung J.; Pieters A.; Asch F.; Graeff-Hönninger S. · Frontiers in plant science · 2026

**Background & Methods** This controlled study examined how drought stress (DS) intensity and timing during flowering affected cannabis production in two CBD-dominant (chemotype III) genotypes. Two DS protocols were tested: moderate DS (substrate dried to 20-30% container capacity before daily replenishment of 50-150 mL) and severe DS (complete water withholding until wilting), each imposed at three flowering stages (early, mid, late), compared to well-watered controls maintained at 60-80% container capacity with 50-300 mL daily supply. **Key Findings** • Moderate drought stress reduced water consumption without negatively affecting inflorescence biomass or CBD yield, making it a viable water-conservation strategy for indoor cannabis cultivation. • Severe drought stress consistently impaired plant performance across all metrics, increased leaf-level water-use efficiency through reduced carbon assimilation (a short-term survival response), and provided no agronomic advantage for cannabinoid production. • Genotype selection exerted substantially stronger influence on productivity and cannabinoid accumulation than irrigation regime, indicating that genetic factors are more critical determinants of yield than drought-stress applications designed to stimulate secondary metabolism. **Dosage & Administration** Not reported. (This study addressed irrigation protocols rather than drug dosing.) **Safety & Adverse Effects** Severe drought stress induced measurable physiological stress responses including reduced relative water content, decreased osmolality, impaired transpiration, reduced photosynthesis, and diminished stomatal conductance, indicating plant distress without corresponding cannabinoid benefits. No adverse effects on human subjects were assessed. **Evidence Quality** This review-type study provides controlled experimental evidence but is limited by examination of only two genotypes under indoor conditions, potentially restricting generalizability to diverse cannabis cultivars and outdoor or greenhouse environments. The findings are level 3 evidence (controlled laboratory study). Key limitations include lack of evaluation across broader genetic backgrounds, absence of economic cost-benefit analysis of moderate versus standard irrigation, and inability to determine whether findings apply to non-CBD-dominant chemotypes. The inconsistency with previous literature on drought and secondary metabolism is acknowledged, suggesting this area requires further investigation across diverse genotypes and cultivation conditions.

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