Date of Award
12-2025
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Plant and Environmental Science
Committee Chair/Advisor
James E Faust
Committee Member
Sruthi Narayanan
Committee Member
William Bridges
Committee Member
Bruce Bugbee
Abstract
Controlled-environment cannabis (Cannabis sativa L.) production is a novel horticultural industry due to long-standing federal prohibitions associated with production, distribution, and consumption of this species. Many cannabis production methods are based on legacy knowledge and hypotheses that often contradict standard practices used in the agriculture and floriculture sectors. During this research, several horticultural practices were evaluated, including shoot number manipulation, fertilizer restriction, harvest timing, and photoperiod manipulation. Shoot number manipulation was achieved by repeatedly pinching apical shoots, which reduced reproductive shoot length (cm/shoot) and improved inflorescence:trim ratio, both of which can reduce material cost in production and labor cost in post-harvest processes. Fertilizer restriction at the start of inductive short-day photoperiod decreased both plant area (m2/plant) and per plant mass measurements (g/plant), but together these changes increased inflorescence and cannabinoid yield (kg∙m-2). Fertilizer restriction prior to harvest, colloquially known as “flushing”, tended to decrease dry mass, cannabinoid yield, and mineral nutrient concentrations, though these changes are thought to improve organoleptic characteristics of dried inflorescences. Harvest timing experiments identified two key temporal trends over a 10-week flowering period, including: 1) linear increase of reproductive mass, and 2) quadratic response of cannabinoid concentration. The ratio of CBD:THC changed little over the flowering period, thus compliance and regulatory sampling can occur at any time during production. Photoperiod manipulation evaluated differences in growth under continuous photoperiod treatments as well as trade-offs associated with initiating inflorescences under one photoperiod and finishing under a different photoperiod at various intervals during the flowering period. Dry mass and shoot length generally increased with photoperiod, though cannabinoid concentration in inflorescence tissue was unaffected and longer photoperiod corresponded with inflorescences lower in organoleptic quality. The results from these studies demonstrate that multiple horticultural strategies are available to improve yield and efficiency during controlled-environment production, but identifying end-product goals e.g., dried inflorescences or extracted concentrates, is critical to balance tradeoffs and maximize overall profitability.
Recommended Citation
Alden, Michael John, "Horticultural Strategies to Improve Yield and Efficiency for Controlled-Environment Cannabis Production" (2025). All Dissertations. 4161.
https://open.clemson.edu/all_dissertations/4161