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.