Severe Drought Significantly Reduces Floral Hemp (Cannabis sativa L.) Yield and Cannabinoid Content but Moderate Drought Does Not

Floral Hemp (Cannabis sativa L.) is a new crop of interest due to its capacity of producing medicinally active substances such as cannabidiol (CBD) and other cannabinoids and low tetrahydrocannabinol (THC). Preliminary experiments performed in high-THC cannabis have found that light drought stress close to inflorescence maturity can increase THC levels raising concerns about the negative effects that drought can have on floral hemp production. Therefore, the objective of this study was to examine the effects of various timings and levels of drought on floral hemp yield, CBD and THC content. The hemp cultivars 'BaOx' and 'Cherry Mom' were planted in a commercial greenhouse setting in 2021 and 2022 and grown under well-watered conditions until flowering, at which drought treatments started. Moderate drought intensities (30–50 % field capacity) did not modify yield or THC and cannabidiol (CBD) levels. However, intense drought treatments led to significantly decreased yield and THC and CBD concentrations. Overall, drought stress reduced the THC percentage less than CBD, therefore decreasing the CBD:THC ratio. This research also demonstrates that intense drought decreases THC and CBD content instead of increasing it.