the science of growing weed

Growing cannabis can be a lucrative business. Spending on legal cannabis in North American medicinal and recreational markets is projected to reach US$21.6 billion by 2021.

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.

In contrast, researchers have been improving production practices for other crops, including medicinal plants, for decades, creating a large body of scientificaly-validated information.

Current state of cannabis production.

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.

In Canada, there are currently 73 authorized licensed medical cannabis producers, most of them large-scale producers. With the recreational use and sale of cannabis scheduled for legalization in our country next year, it is foreseeable that many more large-scale producers will enter the market.

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.

Growing cannabis has been illegal for so many years that scientific research on how to best produce this crop is limited. Much of the knowledge on how to grow cannabis lacks validation, is clouded in secrecy and is mostly connected to hidden and illegal production facilities of the past.

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

University of Guelph provides funding as a founding partner of The Conversation CA.

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.

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In the Canadian medicinal cannabis market, there are strictly enforced quality and safety regulations on products being distributed to patients. However, there is little guidance on production, other than to meet these standards. Governments will have to regulate production practices, with both producer and public interest in mind.

In Canada and around the world, legal cannabis producers face many challenges: Varying government regulations, high security requirements and a lack of reliable information on how to grow their crops.

The production challenges facing large-scale cannabis producers will inevitably be like those producing other greenhouse crops, especially issues with nutrient and disease management. For example, large-scale plant production facilities use large quantities of fertilizers and water. If improperly disposed of, they could pollute the surrounding environment.

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.

Looking to decades of horticultural knowledge.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

Humans have been growing plants in controlled environments for hundreds of years. Over the past 50 years, billions of dollars have been invested into this research field and an enormous amount of knowledge has been accumulated. Cannabis producers can dip into this knowledge pool by working with skilled researchers.

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.

Public policy on cannabis has focused on public health concerns, the illegal market and taxation. With the opening of the recreational market and increased production, regulating production will also be important.

With changing government regulations in Canada, and the many medicinal benefits of cannabis, it is time to move the legal cannabis plant production industry into the realm of high-tech laboratories and scientific practices.

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.

“Because of the federal strictures, there weren’t any standardized methods. Labs had to validate everything themselves,” Brauninger says. “It’s difficult to bring in expertise when there isn’t a wealth of information available, and no trade association to help share techniques.”

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

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.”

Cannabis companies are quickly adopting techniques and technologies that were pioneered by commercial agriculture and horticulturalists. Organigram, a cannabis producer in Moncton, Canada, stringently controls its growing operations, says Jeff Purcell, vice-president of operations. “The growing environment is standardized, and we have full control over the air, light, temperature and fertilizer,” he says. “It’s all highly automated and computer controlled.”

To run these advanced facilities, cannabis companies need researchers who are experienced in plant science, microbiology, chemistry and other scientific disciplines — and they are turning to academia to find them. “Instead of underground growers, they are hiring lots of university-educated and trained people,” says Zheng.

Testing, testing.

“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.

Part of Nature Outlook: Cannabis.

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.

One sign of progress is that cannabis products can be recalled when they fail testing, just like other medical or consumer items. In December 2016 and January 2017, Organigram had to recall some of its products when residues from pesticides not approved for use in cannabis were detected. Although the company’s reputation took a short-term hit, Purcell says that recalls are a sign of the industry’s growing professionalism. Consumers can be confident that cannabis goods have been made “under a controlled, regulated environment and tested in a certified lab that guarantees safety and quality”.

Such labs are beginning to adopt standardized tests for potency and purity using gas chromatography and high-performance liquid chromatography. They are also developing methods to identify and measure levels of THC and other cannabinoids, as well as contaminants such as heavy metals and pesticide residues. “These aren’t necessarily new tests that have been created for this industry, but the type that had to be applied for this product,” says Brauninger.

And as testing becomes more widespread, its importance is also reaching users, says Marcu. “Consumers are starting to realize that there is a big difference between illicit or grey-market products and those from a licensed operator,” he says. “They can have more confidence in the products than before.”

A commercial medical-cannabis cultivation facility in Moncton, Canada. Credit: Organigram Inc.

Organigram’s operation is in stark contrast to the image of an illicit farm hidden in the woods. It is entirely indoors, with 52 identical growing rooms on three floors. Plants are propagated by cloning, rather than grown from seed, so the crop’s genetic identity remains the same from generation to generation. The growers track and log all growing parameters, and then tweak them as needed to maintain consistency. Purcell sees the company’s operation as a ‘manufacturing facility’, rather than a garden or a greenhouse. “There are quality checks like you would see in any manufacturing facility, whether it was producing food or tyres,” he says.

In the United Kingdom, for example, strict rules concerning THC levels in medical cannabis mean that labs can find it difficult to get the sample analytical standards that they need for comparing products. The licences required to handle the standards are the same as those needed by a lab doing research on the drug itself. “It’s ludicrous that analytical standards are so tightly controlled,” says James. “The cannabis products are treated the same as a kilo of cocaine.”

But other issues are unique to cannabis production. And achieving the most efficient production requires growers to do research under controlled conditions to understand how both plant genetics and growing conditions can affect the product.

“Cannabis is just another crop,” he says. “The commercial flower and vegetable industries have been working on the same problems for many years, and they have the technology already.”

Many of his postgraduate students, he says, receive job offers from cannabis companies before they have even completed their studies. Zheng will begin teaching a cannabis production class for undergraduates at the University of Guelph in January 2020, and several colleges in North America already offer courses designed to provide skilled workers to the industry. In April, the first 24 students graduated from an 8-month cannabis production course at Niagara College Canada in Niagara-on-the-Lake. That course, intended for students who already have a diploma or degree in plant science, focuses on how to grow cannabis and the surrounding regulations. Bill MacDonald, a plant scientist and the programme’s coordinator, says that the graduates were snapped up by industry.

For years, the popular image of cannabis growers has been scruffy hippies getting high on their own supply in a disorganized underground economy, rather than shiny white industrial agriculture facilities. Even larger-scale operations involved minimal quality control or lacked formal record keeping.

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.

But as legal medical — and increasingly, recreational — cannabis becomes more widespread, the cannabis industry is becoming more professional. By adopting the methods and rigour of plant science and analytical chemistry, it is ensuring that it can produce safe, consistent and high-quality products for a fast-growing and lucrative market.

Brian Owens is a freelance journalist in St Stephen, New Brunswick, Canada.

Although small-scale growers of illicit cannabis can get away with vague descriptions of strains and considerable variation between batches, commercial producers have to meet the same standards as they would for other consumer products. They need to produce a reliable product and follow the stringent rules and regulations that apply to product labelling and safety in their country.

Many of the challenges of large-scale cannabis production can be solved by drawing on the experience of the commercial greenhouse industry, says Zheng. Growing crops commercially requires a homogenous soil and consistent irrigation. Small variations can mean that parts of the crop dry out at different rates, which leads to the spread of pathogenic agents and root rot, and to an inconsistent product. But the tomato industry, for example, has experience of growing tens to hundreds of hectares of produce at a time, and that expertise can be transferred easily to cannabis growers, says Zheng.

Zheng’s laboratory is one of many that are working with cannabis producers to support and guide this effort. He is studying how the amount and wavelength of light used in growing can affect the plant’s cannabinoid composition. Increasing the amount of ultraviolet light, for example, can increase levels of tetrahydrocannabinol (THC), the main psychoactive component of cannabis. “We want to create a lighting recipe which will help producers get a consistent product,” he says.

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In Canada, government regulations require producers to use an independent lab to measure the level of cannabinoid in dried cannabis flowers and oils so that the resulting products can be labelled appropriately. Producers must also test for contaminants such as the bacterium Escherichia coli , mould, heavy metals and 96 types of pesticide. When edible cannabis products become legal in Canada later this year, they will face similarly stringent rules, says Purcell; labels on such products will have to convey the same nutritional information as do those on any other food product. In the United States, the regulations are broadly similar to those in Canada. But each US state where medical or recreational cannabis is legal sets its own testing regime — and those requirements can vary widely and change quickly. “In Delaware, the regulations are now totally different than two years ago,” says Marcu.

Besides the challenges of growing a sufficient amount of high-quality cannabis for a rapidly growing market, cannabis companies have to deal with something that illegal growers do not — government regulation.

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.

Independent testing labs have sprung up to help growers to meet the requirements, but like the wider cannabis industry, they face growing pains. “At the moment it’s a bit like the Wild West, with different rules in different places,” says Andrew James, marketing director of Ellutia in Ely, UK, which makes chemical analysis equipment for the cannabis industry, among other markets. “It can be hard to know what to test for, how to test and where to do it.”

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.”

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Here’s one to ponder: Where did the weed come from? No, not where it was bought, but where and when was the plant first domesticated?

People feeling the effects of marijuana are prone to what scientists call “divergent thinking,” the process of searching for solutions to a loosely defined question.

Dr. Fumagalli and his colleagues then extracted genomic DNA from the samples and sequenced them in a lab in Switzerland. They also downloaded and reanalyzed sequencing data from 28 other samples. The results showed that the wild varieties they analyzed were in fact “historical escapes from domesticated forms,” and that existing strains in China — cultivated and wild — were their closest descendants of the ancestral gene pool.

“By the way, that’s the reason you call it weed, because it grows anywhere,” he added.

By sequencing genetic samples of the plant, they found that the species had most likely been domesticated by the early Neolithic period. They said their conclusion was supported by pottery and other archaeological evidence from the same period that was discovered in present-day China, Japan and Taiwan.

“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.”

The study was led by Ren Guangpeng, a botanist at Lanzhou University in the western Chinese province of Gansu. Dr. Ren said in an interview that the original site of cannabis domestication was most likely northwestern China, and that the finding could help with current efforts in the country to breed new types of hemp.

It can also be hard to understand precisely how plant species are domesticated in the first place, said Catherine Rushworth, a postdoctoral researcher at the University of Minnesota who studies plant evolution.

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.

“It’s easy to find feral samples, but these are not wild types,” Dr. Fumagalli said. “These are plants that escaped captivity and readapted to the wild environment.”

Genetic sequencing for the latest study suggests that the species has a “single domestication origin” in East Asia, the researchers wrote.

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.

A group of biologists and other scientists said humans began growing cannabis about 12,000 years ago not just for food, but also for hemp and, yes, probably to get high.

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

Farmers began breeding the plant specifically for its mind-altering properties about 4,000 years ago, as cannabis began to spread into Europe and the Middle East, the authors of the study said.

Many botanists believe that the cannabis sativa plant was first domesticated in Central Asia. But a new study published on Friday in the journal Science Advances suggests that East Asia is the more likely source, and that all existing strains of the plant come from an “ancestral gene pool” represented by wild and cultivated varieties growing in China today.

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