Study to Develop a Value for Cultivation and Use (VCU) Field Trial Protocol for Cannabis sativa L. Flower Varieties

Variety testing systems in Europe do not account for cannabis varieties selected specifically for flower and cannabinoid production. These “flower varieties” are morphologically distinct from industrial varieties, with significant implications for agronomic characterization in the Value for Cultivation and Use (VCU) testing system. However, they are not considered as drug-type varieties due to their low Δ9-tetrahydrocannabinol (Δ9-THC) content. Identifying specific traits that can objectively describe these varieties is integral to establishing stable and high-quality production standards. We evaluated specific traits tailored to the VCU testing of flower varieties in two field trials. The assessed phenological traits showed significant differences between varieties (p < 0.0001) for all traits except ease of harvest (EH) and lodging, with significant differences also found in all yield-related traits. The number of branches per plant (NBP), flower and leaf yield (FLY), harvest index (HI) and raceme compactness index (RCI) could therefore be considered for VCU testing. The varieties differed significantly in their cannabinoid content, with all falling below the THC limit under Swiss regulation (1%) but not all meeting the 0.3% limit set by European countries. Variations in THC content were dependent on the testing year, the timing of sampling and the number of plants sampled, underscoring the need to clarify VCU testing methodologies. Incorporating cannabinoid content along with morphological and phenological traits is crucial in introducing a new “flower” category within the VCU system for cannabis.