Cannabidiol industrial hemp growth, biomass, and temporal cannabinoids accumulation under different planting dates in southern Florida

Abstract

Due to limited information, identifying suitable cannabidiol (CBD) dominant industrial hemp (Cannabis sativa L.) cultivars and optimal planting date are critical for hemp commercialization for CBD production in Florida. Two field trials were conducted with seven cultivars planted on three different dates from late April to late June. The cultivars were received from two different suppliers (Kentucky and Colorado) representing their adaptation. Plant growth parameters such as plant height and green canopy cover were recorded at 2−3 weeks intervals during crop growth. Temporal CBD and Δ‐9‐tetrahydrocannabinol (THC) concentrations in developing flowers were analyzed weekly beginning two weeks after flowering until maturity. The final floral biomass yield was measured at harvest. CBD and THC concentration curve over crop growing season varied among the tested cultivars. High positive correlations between CBD and THC concentrations (R2 = 0.88−0.98) were observed in all cultivars. This resulted in similar CBD/THC ratios across all planting conditions. Earlier planting resulted in higher CBD, THC, and floral biomass yield in a few cultivars, with no significant effect in most cultivars. Cultivars adapted in Kentucky performed better compared to Colorado in floral biomass and CBD yield. However, THC concentrations in the cultivars adapted in Kentucky mostly exceeded the acceptable legal threshold (0.3% THC) at harvest. Results indicate cultivar performance was affected more by genetics compared to planting date. Screening more cultivars adapted to regions of similar latitudes and environmental conditions is necessary to identify suitable hemp cultivars for Florida or similar climatic conditions.

Temporal cannabinoids profile and biomass yield in cannabigerol dominant industrial hemp under different planting dates in southern Florida

“…Similarly, the effect of planting date was also not consistent among the locations (Figure 4). In other studies with CBD-dominant industrial hemp cultivars, we also found that the effect of location and planting date was not consistent across the cultivars (Chiluwal et al, 2023;Sandhu et al, 2022). We did not see significant location and planting date effect in most of the tested cultivars possibly due to similar environmental conditions during cannabinoid accumulation across all planting dates and locations in the experimental year.…”

“…Both THC (<0.1%) and CBD (<0.2%) concentration was very low in both cultivars in this study suggesting there was no or little transformation from CBGA and CBG into THC and CBD in all planting conditions and locations. Hence, the results of this study suggest that CBG‐dominant industrial hemp cultivars could be better suited in Florida's environment as most of the CBD‐dominant cultivars often exceed acceptable THC concentration (Chiluwal et al., 2023; Sandhu et al., 2022; Yang et al., 2020;). However, floral biomass yield was low in both cultivars.…”

“…THC concentration exceeding a legal threshold in CBD‐dominant hemp cultivars has become a bottleneck for hemp cultivation for essential oil production in Florida (Chiluwal et al., 2023; Sandhu et al., 2022; Yang et al., 2020). However, previous studies have only evaluated CBD‐dominant hemp cultivars and there is no information regarding the potentiality of growing CBG‐dominant hemp cultivars in Florida and similar other locations.…”

“…However, similar information regarding the effect of the environment on CBG accumulation is not available. The CBD and THC accumulation pattern over crop growing season has been documented in both CBD and THC‐dominant Cannabis cultivars (Calzolari et al., 2017; De Backer et al., 2012; Latta & Eaton, 1975; Pacifico et al., 2008; Sandhu et al., 2022; Chiluwal et al., 2023). However, CBG accumulation pattern in CBG‐dominant cultivars is still unknown.…”

“…Due to its photoperiod sensitivity coupled with comparatively shorter day length in Florida, cultivars from the northern latitude begin the reproductive phase very early in the season without accumulating much vegetative biomass in Florida's environment (Zhang et al., 2021). Similarly, most of the industrial hemp cultivars adapted in other agroclimatic conditions often exceed THC concentration above the limit (>0.3%) when grown in Florida (Chiluwal et al., 2023; Sandhu et al., 2022; Yang et al., 2020). Hence, lack of suitable cultivars with acceptable legal THC concentration and less biomass yield remains the major challenge for its commercialization in Florida and similar other climatic conditions.…”