Harvesting cannabis is a task many amateurs have learned from classic cultivation tomes like Marijuana Horticulture by Jorge Cervantes and the litany of texts from Ed Rosenthal. These leaders in cannabis growing education have learned from teachers, experience, and their peers.
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This work led countless people to grow their own medicinal and recreational pot, creating a new generation of equipped cultivators. Now, as the green rush perks interest in the plant, science is catching up with the culture.
A research paper published in Smart Agricultural Technology used deep learning methods to identify the color and shape of trichomes ready to harvest. Interestingly enough, Ed Rosenthal and David Downs published the same tips in Marijuana Harvest five years earlier. This convergence marks a special time in cannabis history where science meets the culture.
Ed Rosenthal is a leading authority in weed horticulture, educating others for decades on the art of growing. The social activist shared his feelings with GreenState on the scientific validation of his adopted cannabis harvest methods.
“It’s a slow process because farmers have a natural conservatism,” Rosenthal said. “Now, with the scientific advancements in genetics, propagation, and lighting, the next step will be developing more efficient techniques of cultivation.”
Harvest tips become facts thanks to this research paper
Researchers looked for answers in the trichomes of four phenotypes to create more efficient cultivation strategies. The study, funded by Health Canada, took place in a hydroponic commercial greenhouse and looked at four strains.
Pink Kush and White Rhino were cultivated from October to April. Afghan Kush and Green Death Bubba were grown from May to September. These four varieties were originally cloned from mother plants using rock wool cubes before being transferred into coconut fiber blocks.
Image data was collected three weeks into the growth cycle when trichomes became visible. Then again at weeks eight or nine when the flower aged. Researchers used visible fluorescent lighting and ultraviolet light in the captures. They harvested flower and collected data from the top, middle, and bottom branches.
Glands have previously been complicated to observe in this way as they often stick to or hide behind other trichomes, among other segmentation issues. For this study, researchers relied on DO-U-Net to solve this problem. The deep learning neural network segments repeated shapes in aerial images and two-dimensional microscopy.
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The network predicts the edges of the trichome glands, allowing them to be measured individually without a clear shot. Researchers assessed changes in the morphology as the flower aged, plotting roundness, density, regression, and head diameter. What they found validated what Rosenthal has learned and taught for years: it is time to harvest when the trichomes are mostly translucent with a few milky heads.
The master grower came to the same conclusions with ingenuity and persistence over years of cultivating.
“I had used a photographer’s loupe to look at photo slides, so it was natural for me to use it to look at other small things close up,” Rosenthal explained. “Understanding the color tone of the trichomes came from experience, conversations with others, and reading some science papers.”
Cannabis has long remained separate from formal research due to legality and lack of interest, but that never stopped those who loved the plant. While mainstream science ignored weed horticulture, experts earned their stripes in the grow room. Now, as scientific research catches up to the wisdom of the counterculture, we may be entering the crest of cannabis agriculture innovation.
