Role of Planting Date on Yield and Cannabinoid Content of Day-neutral and Photoperiod-sensitive Hemp in Georgia, USA

Abstract

Industrial hemp (Cannabis sativa) cultivars used for flower, fiber, or seed production are usually considered short-day plants and flower in response to photoperiod. However, some cultivars of hemp are day-neutral, where flower induction may be independent of daylength. Day-neutral cultivars of hemp were planted before recommended dates and studied in field experiments conducted in Watkinsville, GA, in Spring 2020 and 2021. Day-neutral cultivars (Pipeline and Maverick) and photoperiod-sensitive cultivars (Von and Whitehouse Cherry) were planted on 9 and 25 Apr and 11 and 28 May to determine the impact of planting date on hemp flower yield and quality. Planting date did not impact yield of the photoperiod-sensitive cultivars, but yields of day-neutral cultivars decreased as planting date progressed. Average yields of photoperiod-sensitive plants were greater than the day-neutral cultivars in both study years. Cannabinoid concentrations in flowers were affected by cultivar and study year but were not impacted by planting date. Cannabidiol was the most prevalent cannabinoid in flower tissue with concentrations ranging from 6.5% to 10.5%. Flower biomass yields suggest that the spring hemp planting season may be extended using day-neutral cultivars in the southeastern United States.

Cadmium exposure is associated with increased transcript abundance of multiple heavy metal associated transporter genes in roots of hemp (Cannabis sativa L.)

“…In experiment 2, these threshold levels were exceeded even under the 0 mg·L -1 Cd treatment, suggesting that changes in environmental conditions between experiment 1 and 2 may have influenced total THC content. It is not uncommon for high CBD hemp cultivars, such as Purple Tiger, to have THC concentrations exceeding the 0.3% threshold ( Stack et al., 2019 ; Yang et al., 2020 ; Coolong et al., 2023 ). Although variation in cannabinoid concentrations is largely impacted by genetics, it is also understood that there are genetic and environmental interactions that may impact cannabinoid concentrations ( Trancoso et al., 2022 ).…”

Cadmium Bioconcentration and Translocation Potential in Day Neutral and Photoperiod Sensitive Hemp Grown Hydroponically for the Medicinal Market

“…Plant height was determined by measuring the distance from the base of the stem to the tip of the apically dominant flower at harvest [11].…”

“…Subsamples were taken from the air-dried materials and further dried in a forced air oven set at 55 • C for 48 h until a constant weight was achieved. The dry weights of the whole plant samples were then normalized based on subsample moisture content [11].…”

“…Advantages of DN hemp varieties include the ability to flower in regions that have little variation in photoperiod throughout the year (tropics) or during times of the year when photoperiods may be inadequate to grow DLS varieties. However, many DN types of hemp have been reported to be particularly sensitive to environmental stressors such as high temperatures and may have lower yields than comparable DLS varieties [11].…”

Gene Dosage at the Autoflowering Locus Effects Flowering Timing and Plant Height in Triploid Cannabis

“…As a result, moisture-related diseases, including Fusarium and Botrytis, are a problem for late-to-harvest crops (Darby et al 2021a). Autoflowering plants offer the benefit of quicker harvest (45 to 75 d), but they yield half as much flower per unit area as photoperiod-sensitive plants (Coolong et al 2023). It may be possible to complete two crop cycles per growing season using autoflowering plants; however, the second crop will be affected by the same problems that affect late-harvest photoperiod-sensitive plants.…”