Editor's Note
A field study was performed to investigate the development of cannabinoids in flowers of industrial hemp using three day-length-sensitive and two day-length-neutral varieties. Flower samples were analyzed for cannabinoids on a weekly basis from two to four weeks postanthesis to plant senescence. Results indicate that total THC, CBD, and CBG significantly increased as flowers matured, reaching the greatest concentration during six to seven weeks postanthesis.
Summary

A field study was performed to investigate the development of cannabinoids in flowers of industrial hemp using three day-length-sensitive and two day-length-neutral varieties. Flower samples were analyzed for cannabinoids on a weekly basis from 2 to 4 weeks postanthesis to plant senescence. Results indicate that total THC, CBD, and CBG significantly increased as flowers matured, reaching the greatest concentration during 6 to 7 weeks postanthesis. After a plateau stage of varied length for different varieties, the peak concentrations declined as plants senesced. Total THC was above the 0.3% threshold from 4 weeks postanthesis to the end of the growing season for day-length-sensitive varieties, but this only occurred during 6 to 7 weeks postanthesis for day-length-neutral varieties. The CBD/THC ratio in flowers dynamically changed during the entire reproductive stage for all of the evaluated varieties. The current study provides vital information for successful cultivation of industrial hemp.

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