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authors: Ashleigh Ahrens , David Llewellyn and Youbin Zheng *
School of Environmental Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada;
aahrens@uoguelph.ca (A.A.); dllewell@uoguelph.ca (D.L.)
* Correspondence: yzheng@uoguelph.ca
VIDEO SUMMARY
Practical Breakdown
This study evaluates the response of two ‘type II’ cannabis varieties to different photoperiod durations: a 12-hour light cycle and a 13-hour light cycle.
In commercial cultivation, it is standard practice to transition plants to a 12-hour photoperiod to induce the reproductive or generative phase, maintaining this cycle from initiation to harvest. This study highlights the photoperiodic plasticity of cannabis, demonstrating that different varieties may require distinct critical night lengths to trigger and sustain the reproductive phase.
Additionally, the findings suggest that extending the photoperiod beyond the conventional 12-hour cycle can positively impact plant performance. By increasing the daily light integral (DLI), growers may achieve enhanced yields, offering new opportunities for optimizing cannabis production.
Key Findings
1- Both varieties demonstrated a significant increase in yield under the 13-hour light cycle, with ‘Incredible Milk’ producing 1.35 times more yield and ‘Gorilla Glue’ achieving a 1.5-fold increase compared to the 12-hour cycle.
2- Under the 13-hour photoperiod, both varieties exhibited more robust plant architecture by the end of the flowering stage, indicating enhanced structural development.
3- The variety ‘Incredible Milk’ experienced a slight delay of 1.5 days in flower onset and showed a reduction in apical bud density under the extended light cycle.
Application for cultivators
1- Evaluate the critical photoperiod requirements of your specific commercial varieties to optimize their potential yield. Understanding these requirements will enable growers to maximize productivity.
2- Assess the morphological responses of your commercial cultivars to varying photoperiods to strategically influence overall canopy architecture and improve plant management.
3- Use photoperiod manipulation as a crop steering tool to adjust maturation times, enhancing operational efficiency and streamlining production cycles
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