Too Dense or Not Too Dense: Higher Planting Density Reduces Cannabinoid Uniformity but Increases Yield/Area in Drug-Type Medical Cannabis

Abstract

A major challenge for utilizing cannabis for modern medicine is the spatial variability of cannabinoids in the plant, which entail differences in medical potency. Since secondary metabolism is affected by environmental conditions, a key trigger for the variability in secondary metabolites throughout the plant is variation in local micro-climates. We have, therefore, hypothesized that plant density, which is well-known to alter micro-climate in the canopy, affects spatial standardization, and concentrations of cannabinoids in cannabis plants. Canopy density is affected by shoot architecture and by plant spacing, and we have therefore evaluated the interplay between plant architecture and plant density on the standardization of the cannabinoid profile in the plant. Four plant architecture modulation treatments were employed on a drug-type medicinal cannabis cultivar, under a density of 1 or 2 plants/m2. The plants were cultivated in a naturally lit greenhouse with photoperiodic light supplementation. Analysis of cannabinoid concentrations at five locations throughout the plant was used to evaluate treatment effects on chemical uniformity. The results revealed an effect of plant density on cannabinoid standardization, as well as an interaction between plant density and plant architecture on the standardization of cannabinoids, thus supporting the hypothesis. Increasing planting density from 1 to 2 plants/m2 reduced inflorescence yield/plant, but increased yield quantity per area by 28–44% in most plant architecture treatments. The chemical response to plant density and architecture modulation was cannabinoid-specific. Concentrations of cannabinoids in axillary inflorescences from the bottom of the plants were up to 90% lower than in the apical inflorescence at the top of the plant, considerably reducing plant uniformity. Concentrations of all detected cannabinoids in these inflorescences were lower at the higher density plants; however, cannabinoid yield per cultivation area was not affected by neither architecture nor density treatments. Cannabigerolic acid (CBGA) was the cannabinoid least affected by spatial location in the plant. The morpho-physiological response of the plants to high density involved enhanced leaf drying at the bottom of the plants, increased plant elongation, and reduced cannabinoid concentrations, suggesting an involvement of chronic light deprivation at the bottom of the plants. Therefore, most importantly, under high density growth, architectural modulating treatments that facilitate increased light penetration to the bottom of the plant such as “Defoliation”, or that eliminated inflorescences development at the bottom of the plant such as removal of branches from the lower parts of the plant, increased chemical standardization. This study revealed the importance of plant density and architecture for chemical quality and standardization in drug-type medical cannabis.

Correlations among morphological and biochemical traits in high‐cannabidiol hemp (Cannabis sativa L.)

“…In many species, variation in light penetration has been shown to contribute to intra‐plant variation in secondary metabolites, including: flavonoids (Del Valle et al, 2018 ), anthocyanins (González‐Talice et al, 2013 ), and tannins (Mole et al, 1988 ). Recently, Danziger and Bernstein ( 2022 ) found that increased shading as a result of greater planting density decreased cannabinoid concentrations in axillary inflorescences from the bottom of the plant. Additional work examining light penetration into the canopy, photosynthetic activity throughout the canopy, and sub‐canopy lighting will provide a better understanding of the degree to which variability in light intensity modulates variation in cannabinoid concentration.…”

Yield and content of cannabidiol (CBD) and tetrahydrocannabinol (THC) in medicinal cannabis (Cannabis sativa) grown in the Ecuadorian highlands

“…Arsenault et al (2024) also evaluated Δ 9-THC and total CBD in 14 cultivars of hemp, demonstrating that both CBD and THC increase rapidly over a 1-2-week time frame with maximum concentrations (about 16% and 0.6%, respectively). However, the increase in THC and CBD in C. sativa is not yet defined, it is known to be related to soilclimatic conditions and even the availability of nutrients (Danziger andBernstein, 2022, Saloner and.…”

Selected cannabis cultivars modulate glial activation: in vitro and in vivo studies

“…The biological effect of cannabis Fleisher-Berkovich et al Journal of Cannabis Research (2024) 6:25 cultivar extracts may therefore have higher efficacy compared to treatments with only individual cannabinoids (Comelli et al 2008). The production of bioactive compounds in the cannabis plant is affected by genetics (Shiponi & Bernstein 2021b), location in the plant (Bernstein et al 2019), and by cultivation conditions Bernstein 2021, 2022a;Danziger and Bernstein 2022). Since the secondary metabolite profile in cannabis varies between plant cultivars (Danziger & Bernstein 2021a;Saloner & Bernstein 2022b), so may their beneficial effects against neuroinflammation.…”