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the science of growing weed

The science of growing weed

Light emitting diode (LED) technology) is rapidly developing, with dramatic increases in energy efficiency and decreases in price. LEDs can provide different light colours and spectral combinations as needed. Research tells us that we can use light colour and intensity to steer plants to produce desired characteristics and chemical components. However, there is hardly any published scientific research on how to use this modern technology to produce high quality cannabis — information that cannabis growers certainly need.

In the past, indoor cannabis production was largely confined to smaller-scale operations. Under these conditions, growers accumulated enormous levels of knowledge and experience. But much was kept as trade secrets and most still needs to be scientifically validated.

University of Guelph provides funding as a member of The Conversation CA-FR.

Even in today’s modern medicinal cannabis production facilities, growers are often reliant on online forums — so-called “grow guides” — and advice from salespeople for information on crop production. Without proper training, it can be hard to tell fact from fiction.

Looking to decades of horticultural knowledge

We must sift through accumulated grower knowledge, while publicly documenting and improving production practices. Evidence-based research will help growers produce more consistent, high-yielding and high-quality products and help inform policy makers as they regulate this industry.

Growers may also decide to reuse their nutrient solution, but doing so risks spreading pathogens from one infected plant to the whole operation. Through collaboration with horticultural scientists, large-scale producers will have access to many different technologies and strategies to treat irrigation water for reuse or discharge. This will help combat potential problems.

As researchers who study how to produce high-value plants (e.g. medicinal, nutraceutical, edible and ornamental plants) under controlled environments — including indoor medical cannabis — we believe this will require collaborative research among cannabis growers and researchers.

Current state of cannabis production

Unfortunately, reliable evidence-based research is lacking. As mentioned, the bulk of production knowledge is anecdotal and even secretive. It makes things difficult for policymakers charged with setting standards and policies.

Another example involves artificial lighting for plants. In the past, most operations were using high pressure sodium (HPS) lamps as growing lights. HPS is not efficient in converting electricity to light for plant growth, and lighting is one of the major costs for indoor plant production.

The science of growing weed

“For a product to be sold in most US states, it has to be tested externally,” says Jahan Marcu, director of experimental pharmacology and behavioral research at the International Research Center on Cannabis and Mental Health in New York City.

As the cannabis industry expands, the role of good science within it will also expand, and there will be further opportunities for collaboration. “More and more,” says Zheng, “the scientific community and industry are directly communicating and sharing information.”

A student inspects a cannabis plant at Niagara College Canada’s teaching laboratory in Niagara-on-the-Lake, Canada. Credit: Niagara College

Testing, testing

The large-scale, controlled environment enables Organigram to conduct systematic, controlled trials and to produce huge amounts of data — with 5 cycles of growth per year in each of the growing rooms, it can generate more than 250 generations’ worth of growing data each year, says Purcell. The company can use those data to determine what works best for the plants, and then replicate those conditions at scale. “That’s the big difference with the black market,” he says. “When you scale up, you have to take a data-driven approach.”

A2LA is also helping labs to attain ISO/IEC 17025 accreditation, the main international standard for testing and calibration labs. It covers all phases of lab operation, including staff training, data protection and dealing with conflicts of interest.

And not all analytical labs are up to the job. Roger Brauninger, biosafety programme manager at the American Association for Laboratory Accreditation (A2LA), a non-profit organization in Frederick, Maryland, says that although US states introduced requirements for external testing as medical or recreational cannabis became legalized, there was rarely any infrastructure or expertise in place to facilitate a professional testing regime. Even the most established labs, located in California, have only been around since the mid-2000s — despite the state legalizing the medical use of cannabis in 1996.

That led to labs being set up quickly with old equipment in unsuitable spaces, and with minimal quality control. James says that, in the past, it was not uncommon to meet people at trade shows who had bought analytical kits on the online auction site eBay and were running testing labs from their bedrooms.

The science of growing weed

“That seems to be the most pressing problem for humans then: How to get food,” said Professor Purugganan, who was not involved in the research. “The suggestion that even early on they were also very concerned with fiber and even intoxicants is interesting. It would bring to question what were the priorities of these Neolithic societies.”

Michael Purugganan, a professor of biology at New York University who read the study, said the usual assumption about early humans was that they domesticated plants for food.

Although scientists can make some basic predictions about how a given plant species will diverge in nature, she added, such predictions “go out the window” when a natural selection process is driven by humans.

Luca Fumagalli, an author of the study and a biologist in Switzerland who specializes in conservation genetics, said the theory of a Central Asian origin was largely based on observational data of wild samples in that region.

“I would like to see a much larger study with a larger sampling,” he said.