An introduction to cannabis cultivation
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- Local cannabis cultivation laws and regulations
- Cannabis plant sex and anatomy
- The three main growing environments for cannabis
- Cannabis propagation techniques
- Selecting a cannabis growing medium
- Cannabis vegetation
- The cannabis flowering phase
- Harvesting your cannabis
- Cannabis storage tips
- Local cannabis cultivation laws and regulations
Our relationship with cannabis arguably begins and ends with cultivation. All forms of cannabis that we consume derive from a cultivated plant. The value of the cannabis plant, medicinal or otherwise, is largely dependent on what we do with it — how and when we grow it, how we refine it for our own consumption, and even what words we use to describe it.
Cannabis is a dioecious plant, meaning it can be categorically divided into male and female plants. Photo by: Gina Coleman/Weedmaps
Cannabis is a dioecious plant, meaning it can be categorically divided into male and female plants. Male plants produce the pollen necessary for a female plant to produce seeds, while the female plant is the one to naturally produce more of the major cannabinoids, namely cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA), which convert to CBD and THC, respectively. Cannabis also produces several other valuable compounds, such as terpenes and flavonoids, that potentially work synergistically with the cannabinoids to enhance desired and therapeutic effects .
While still highly debated, most countries only recognize one cannabis species, Cannabis sativa L., but some recognize up to three species — C. sativa, C. indica, and C. ruderalis — based on geographic origin, genetics, and morphology. The central difference between today’s indica and sativa plants is in their observable traits during the cultivation cycle.
Indica plants tend to grow short with thick stems and broad, deep-green leaves. They also have shorter flowering cycles, and grow sufficiently in cold, short-season climates. Sativa plants have longer flowering cycles, fare better in warm climates with long seasons, and usually grow taller with relatively light-green, and narrow leaves.
Knowing the morphological, or physical, form differences between indica and sativa plants is more useful to growers and cultivators than virtually anyone else in the cannabis space, despite the terms’ common use in the consumer marketplace.
Every part of the cannabis plant is usable. Historically, cannabis has been bred by humans for three distinct purposes:
- Fiber – harvesting cannabis stalks, typically from hemp varieties.
- Seeds – harvesting seeds from a female hemp plant for its rich oil and protein content.
- Drug-type cultivars – harvesting cultivated varieties for their psychoactive and therapeutic cannabinoids.
From seed to harvest, the cannabis plant’s growth cycle can last anywhere from 10 to 26 weeks. The cycle has three main stages: germination, vegetation, and flowering. Like most plants, cannabis requires light, air, nutrients, and a medium to house its roots. The amount and duration of light the plant is exposed to dictates which growth stage it will be in.
Local cannabis cultivation laws and regulations
In most countries and local jurisdictions where cannabis is legal — medically or recreationally — some sort of home growing is typically allowed, but growing laws vary significantly from country to country and even city to city. If you’re a prospective or current home grower, you should know the laws and regulations of your jurisdiction.
Cannabis plant sex and anatomy
Male and female cannabis plants share a common basic anatomy of roots, stems, and leaves. Both plant sexes produce trichomes , the glandular appendages on the surface of the flower that produce and hold the plant’s cannabinoids and terpenes , however, the female plant produces far more trichomes than the male plant. Beyond these basics, cannabis anatomy varies significantly between male and female plants.
Both plant sexes produce trichomes, however, the female plant produces far more trichomes than the male plant. Photo by: Gina Coleman/Weedmaps
Over the course of our shared history with cannabis, authors, scientists, growers, and industry insiders have used competing terms to describe the same reproductive plant anatomy. Due to an extensive period of prohibition, botanical terms have been frequently misused or replaced entirely. What’s more, popular colloquial terms have become interchangeable despite having different meanings.
So, let’s alleviate some of the confusion and map out the anatomy of both plant sexes by first identifying botanical terms, then clearing up some of the common colloquialisms we’ve inherited.
Anatomy of the female plant
The female cannabis plant is a pistillate, meaning it has pistils and stigmas. You may have heard female cannabis plants referred to as “sinsemilla,” translated from Spanish as “without seeds.” Sensemilla refers to all non-pollinated female plants. Sensemilla plants are ideal for marijuana growers because they offer the highest potential yield of cannabinoids. Pollinated female flowers, or female flowers with seeds, produce a less desirable product than flowers from seedless marijuana.
The reproductive anatomy of the female plant includes:
- Colas: The flowers produced by the female plant. Colas are covered with cannabinoid- and terpene-rich trichomes and commonly called buds or nugs. A cannabis bud is not to be confused with the botanical definition of the word bud: a newly emerging plant.
- Bracts: Small, scale-like leaf structures that encapsulate and protect the seeds. Bracts are often referred to as calyxes, though this term is botanically incorrect. The female cannabis plant does, however, have calyx cells within the delicate layer of tissue between the seed and the bracts that encapsulate it.
- Stigmas: The reproductive parts of the cannabis plant, which catches pollen from the male plant. Stigmas are commonly and incorrectly referred to as pistils. Two stigmas protrude from one pistil.
- Pistil: The reproductive parts of the female cannabis flower that are activated if pollen is captured by the stigmas.
- Sugar leaves: The small leaves that hold cannabis buds together. They are called sugar leaves due to the high concentration of trichomes that have a sugarlike appearance.
Anatomy of the male plant
The male cannabis plant is a staminate, meaning it has stamen or pollen-producing reproductive organs. Male plants are sometimes cultivated for fiber and are more commonly used for breeding new varieties of intoxicating cannabis. During their flowering phase, male cannabis plants release pollen, which will prompt a female plant to start producing seeds. This practice diverts energy from flower production and reduces the overall yield. To maximize your flower yield and prevent seed production, keep male and female plants separated.
The male cannabis plant is capable of producing cannabinoids, but its trichomes are sparsely dispersed across its surface. Males do not produce nearly as many trichomes as a female.
The reproductive anatomy of the male plant includes:
- Stamen: The organ of the male plant that produces pollen and releases it into the wind, where it may be carried to the stigma of a female plant for pollination.
- Anther: The sacks that produce and hold pollen within the stamen. Anthers hang by a small filament. Together, the anther and the filament make up a stamen.
- Pollen: Microscopic grains produced and contained in the anther that fertilize the female plant when released.
A hermaphrodite is a rare monecious plant, meaning it develops both male and female sex organs. The term monecious stems from the root “mono,” meaning “one.” While there are multiple reasons that a plant may exhibit both signs, hermaphrodites are primarily formed if a female plant is exposed to extreme conditions during key stages of growth, such as insufficient light or harsh environmental conditions. Signs of a hermaphrodite typically show late into flowering.
In a final attempt to continue their seed line, a sensemilla crop will occasionally produce a few hermaphrodites. While the pollen of these hermaphrodites is frequently unviable, marijuana growers should remove hermaphrodites when they occur to eliminate the risk of pollination. Hermaphrodites will also produce a lower overall flower yield as the plant is forced to divert energy into the production of seeds that would have otherwise been used for the production of trichome-rich flowers.
The three main growing environments for cannabis
How to grow marijuana outdoors
Growing marijuana outdoors exposes a crop to the elements, offering natural light and significantly reducing costs for growers. With no artificial lights or fans required, electricity may only be required for irrigation.
While exposure to a natural environment is generally good for plants, exposure to harsh environmental conditions may present hindrances to an outdoor crop. Rain, insects, invasive plants such as thistle, animals, and extreme weather conditions are all potential crop killers. Outdoor cultivation also limits cultivators’ control over environmental crossover from neighboring fields. In short, your fellow farmer’s pesticides could end up being your pesticides if they’re not expertly applied.
Outdoor cannabis cultivation relies on the available sunlight during the changing seasons, during which the plant is exposed to the full spectrum of light available in nature at that time of year. Outdoor cultivators experience a longer growth cycle and typically only harvest once a year.
How to grow marijuana in a greenhouse
Growing cannabis in a greenhouse offers the free sunlight of an outdoor grow, but with far greater environmental control. Greenhouses allow growers to control natural light with a blackout shade or similar roof covering system. Greenhouses also offer the option to add electrical lighting to supplement sunlight on cloudy days and an added layer of protection from animals, pests, and extreme environmental changes.
One of the downsides to greenhouse cultivation is the upfront cost required to have such a structure. Greenhouses range from temporary structures made of plastic and PVC pipe to permanent structures that allow growers to control every environmental aspect and utilize advanced cultivation methods, including light deprivation.
A risk in greenhouse growing is that pests can spread inside the enclosed environment at a faster rate. Protection against environmental crossover is also limited depending on the type of greenhouse structure.
How to grow marijuana indoors
Growing marijuana indoors usually means a warehouse setting, which requires artificial lighting and use of air conditioning and dehumidification systems. The intention of an indoor setup is to mimic the elements of the outdoors that facilitate plant growth while maintaining full control over every environmental parameter. High upfront costs, including the building structure, equipment, water, electricity, and other utilities, is the major downside of growing marijuana indoors for beginners .
Cannabis propagation techniques
How to grow marijuana for beginners
Propagation encompasses the entire growth cycle from start to harvest. Cannabis can be grown either from seeds or a cutting (clone) from another plant.
Cannabis seeds, formed when pollen fertilizes the female plant, are ready to plant and grow as soon as they successfully germinate, or once the root has broken through the seed. While you can plant your seeds directly into the ground, it’s recommended to germinate them in a moist paper towel before planting. Home cultivators often start with feminized seeds to ensure that the adult plant is a flowering female.
Propagation through seeds is commonly known as sexual propagation, and is an often preferred method for outdoor cannabis cultivation because it makes for a more durable plant. Not only do sexually propagated crops have a greater yield potential than clones, they’re also more resistant to pests, illnesses, and diseases.
The most frequently cited disadvantage of growing plants from seeds is inconsistency. Plants propagated by seeds do not maintain the exact phenotype, or observable physical characteristics and chemical traits, of the parent plant. This causes variances and inconsistencies in the cannabinoids and terpenes that growers and consumers may find undesirable.
While most growers want uniform plants, occasionally growers will grow a large amount of plants from seeds so they can choose plants that produce unique physical and aromatic characteristics. This practice is commonly referred to as pheno hunting and is practiced by most nurseries.
Asexual propagation, also known as cloning, is the replication of a single parent plant outside the means of sexual reproduction. Cannabis clones typically start with a cutting of a stable mother plant, which is likely to grow into a genetically similar plant under the right growth conditions. A clone’s central purpose is to reproduce and preserve the genetic identity of a cannabis plant. When grown under the exact same environmental conditions as the mother plant, a clone is infinitely more likely than a plant grown from seed to exhibit the mother plant’s physical traits, as well as its cannabinoid and terpene profile. It should also mirror the mother’s ability to take in nutrients and resist pests or fungi.
Because they’re not exposed to the genetics of multiple plants — instead receiving the same genetic code as the mother plant — clones stand a far better chance of preserving the desired characteristics of the mother. Plants grown from clones also allow growers to determine which environmental conditions will maintain those ideal genetics, and determine optimal feeding schedules, flowering times, and nutrient recipes.
Lack of genetic diversity is a good thing for growers, but it can also have catastrophic consequences. If plants are exposed to adverse environmental conditions for which they have no genetic defense, an entire crop can be wiped out.
Selecting a cannabis growing medium
Whether a plant is grown from a clone or seed, it needs a medium to serve as a base for a healthful life. A growing medium is the material in which plants are set during the growth cycle. Whether you use hydroponics , aeroponics , or traditional soil cultivation, your selected growing medium needs to provide the plant’s roots with air, water, and nutrients.
Soil is the most common medium for growing cannabis. Healthful soil is an exceptionally stable growing medium, allowing for sufficient moisture retention that provides the grower ample time between watering sessions. Soil is readily available and relatively easy to work with, which makes it an effective growing medium for the widest spectrum of growers — from prospective home growers to bona fide experts. Soil can be used for both indoor and outdoor growing.
Hydroponic cultivation is the preferred medium for indoor cultivators, feeding plants through a nutrient-rich liquid solution. Perlite, vermiculite, coco coir, and hydroton balls are all commonly used hydroponic media, which allow for optimal uptake of nutrients and reduced water usage compared with soil. Hydroponic methods are also frequently used in greenhouse settings, but not commonly used for outdoor growing.
The major downside of hydroponics is the rigorous attention to detail the practice requires. Hydroponic media are much more sensitive to severe temperatures. Too much heat, in particular, can be very damaging as it invites bacteria and disease. Meanwhile, the water’s pH and nutrient levels must be consistently monitored to ensure the plant is getting what it needs to grow strong.
Aeroponics function similarly to hydroponics, but rather than maintaining the plant’s roots submerged in water, an aeroponic system suspends the plant’s roots in an environment of mist and air where they absorb water, nutrients, and oxygen. An aeroponic system arguably has the most potential for maximum yield, but it’s also much more temperamental than other systems. Both environmental and growth control factors must receive careful, constant attention for an aeroponic system to be effective.
Germinating seeds or rooting cannabis clones
The germination phase takes place from the moment a seed’s embryo is exposed to water until the seed has sprouted its plumule, or initial taproot. Germination only occurs when plants are grown from a seed, and usually takes between 12 hours and three weeks, depending on the vitality of the seed, age of the seed, and germination techniques selected by the grower.
The simplest way to germinate a cannabis seed is by placing it about 3 millimeters deep in moist soil. Germination soils are also an option, designed with micronutrient blends that facilitate healthy sprouting. Many growers prefer towel germination, in which seeds are placed between two damp paper towels, then immediately transferred into a growing medium once the taproot is exposed.
Many growers prefer towel germination, in which seeds are placed between two damp paper towels, then immediately transferred into a growing medium once the taproot is exposed. Photo by: Gina Coleman/Weedmaps
If growing from a clone, the rooting phase is the time in which the plant develops its taproot. During this time, the young cutting is exposed to 24 hours of light in an environment with high humidity. This can take anywhere from 3 to 14 days.
The vegetative phase is when the plant grows its roots, stalks, and large fan leaves that will structure the plant. Fan leaves will ultimately be used to convert the sunlight into the sugars that the plant needs to produce the flowers or seeds. The light cycle is typically reduced to 18 hours of light, as it requires a minimum of 16 hours of light to maintain the plant. During cannabis vegetation, cultivators can train their plants or manipulate their growth patterns for a multitude of reasons. Indoor growers may want to train their plants to stay short by growing horizontally, while indoor and outdoor growers may want to force their plant to develop multiple flower growth sites at the same level.
There are several training techniques indoor growers deploy to get an optimal yield out of their plants within limited space and lighting conditions. All of them involve manipulating the shape and growth of the plant, usually by bending the stem in some fashion or another.
Sea of green (SOG)
The Sea of Green (SOG) technique involves growing several small plants instead of a few large ones with the intention of maximizing space and cultivating single colas. With the proper setup, a SOG grow promotes the shortest vegetative phase to produce short and dense colas.
Low stress training (LST)
Low Stress Training (LST), like most training methods, involves bending and tying down stems for maximum yield and light exposure within a finite space. The “low stress” element of LST refers to manipulating stem growth in favor of extreme bending to prevent the stress that results from breakage or cutting.
You might think of super cropping as the opposite of LST in that it features strategically executed forms of “high stress,” rather than sustained forms of minimal stress. This method uses targeted stress to encourage cannabis plants to produce more of the cannabinoids and terpenes they develop for protection.
Strategically planned and executed stress on the plant is intended to initiate a defensive reaction, thereby increasing the plant’s cannabinoid and terpene production. This type of sustained stress is usually achieved by pinching targeted areas of the stems and tying them down. When growers accidentally apply too much stress, they typically apply duct tape to the damaged area to help the plant heal.
Screen of green (SCROG)
The Screen of Green (SCROG) method uses LST or Super Cropping to inhibit vertical growth of the cannabis plant by encouraging horizontal growth. This is done by forcing the plants to grow through a suspended horizontal screen. As the crop stems spread laterally across the screen, colas form in otherwise dormant areas of the stem. This technique is used where local laws limit the amount of plants that can be cultivated at one given point, allowing growers to make use of a larger amount of area.
The SCROG method uses LST or super cropping to inhibit vertical growth of the cannabis plant by encouraging horizontal growth. Photo by: Gina Coleman/Weedmaps
Lollipopping is removing growth from the lower portion of the plant to divert energy to the higher branches that produce colas, resulting in a “lollipop”-shaped plant. This technique is especially handy for indoor setups that offer minimal light to lower branches and often used on SCROG grows.
Topping and fimming (FIM)
Topping consists of clipping the growing tip of a plant’s main stem at a 45 degree angle that causes two colas to form instead of one. This method is used to prevent the plant from growing like a Christmas tree by stopping the vertical growth of the main stalk and allowing the lower growth tips an opportunity to catch up. Growers can also “top” a plant multiple times to turn two growth tips into four, and so on.
The FIM method, or fimming, is an offshoot of topping, and derived from topping a plant imprecisely (hence the name FIM, which stands for “F**k, I missed”). Rather than cut the whole tip of a cannabis plant at a 45 degree angle, fimming involves pinching off most of the cannabis tip with the goal of growing four colas immediately in the place of one.
Removing fan leaves
Removing fan leaves from the plant can be considered a training technique that aims to divert the plant’s energy into producing larger colas by limiting the amount of foliage that the plant needs to maintain and increasing the amount of direct light to any growth sites below the canopy. It also helps reduce the likelihood of a pest or mildew infestation. However, fan leaves do take in light and provide energy for the plant, so growers should use caution when removing them.
Removing fan leaves from the plant can be considered a training technique that aims to divert the plant’s energy into producing larger colas. Photo by: Gina Coleman/Weedmaps
The cannabis flowering phase
The flowering phase is when the female plant produces trichome-covered colas and when the male plant produces and releases its pollen. Cannabis plants flower naturally during the 12/12 photoperiod when the plant receives 12 hours of light and 12 hours of darkness. In nature, daylight hours are optimal for cannabis plants flowering from July to November in the Northern Hemisphere. On the autumnal equinox in September, the sun is in the sky for 12 hours of the day, with daylight hours slowly reducing until and through the winter. The opposite is true in the Southern Hemisphere.
The flowering phase is when the female plant produces trichome-covered colas and when the male plant produces and releases its pollen. Photo by: Gina Coleman/Weedmaps
Indoors or in a light-controlled greenhouse, introducing an artificial 12/12 light cycle will force a cannabis plant to flower.
When is cannabis ready for harvest?
A female plant is generally ready to harvest when the glands on the top of the capillary stalked trichomes turn from clear to a milky white color. Some cultivators are also able to use the color of the stigmas to time their harvest. Stigmas tend to change from either white to orange or red to brown. Growers should also be aware of the typical flowering times of the cultivars they’re growing.
Harvesting your cannabis
Once the cannabis plant is ready for harvest, its precious and delicate trichomes are in one of their most vulnerable states. Overexposure to oxygen, light, and/or heat may degrade cannabinoids and terpenes, or activate them prematurely. Trichomes become more fragile and therefore more susceptible to breaking off the plant if mishandled under extreme conditions. When harvesting cannabis plants, growers should implement methods of drying, trimming, and curing that reduce the amount of agitation the plant experiences in order to limit any damage to the trichome glands.
When your cannabis is ready to harvest, cut the whole plant at the base or cut the plant into large branches. Hang your plant or cuttings upside down on a clothesline in an environment that is not overly dry or humid. At this point, some growers begin manicuring their plants by cutting off all remaining fan leaves and some of the sugar leaves. Plants should be left hanging upside down to dry until the stems slightly snap when bent.
Avoid losing trichomes by not letting your branches hit any surfaces while hang-drying. Contact with a surface can damage the trichomes and could cause them to break off the plant. Depending on environmental conditions, the initial drying process usually takes three to seven days.
The trichome gland will experience a few changes during the drying process. The most noticable is a loss of the extremely pungent smell. This is due to a loss of the most temperature sensitive terpenes, or hydrocarbon compounds that produce each cultivar’s unique aroma. Studies have found that upwards of 30% of monoterpenes, or terpenes with two isoprene units — as opposed to the three isoprene units of sesquiterpenes, four isoprene units of diterpenes, and so on — produced during the flowering phase are lost in the drying process. Additionally, when cannabis is dried, terpene compounds are oxidized, and the terpene technically becomes a terpenoid.
Once the initial drying is complete, it’s time to finish trimming and manicuring your bud. Cannabis is typically trimmed to remove the excess sugar leaves that, while consumable, have a smaller concentration of trichomes than the flower and can be harsh when smoked. Sugar leaves aren’t normally discarded, however, as they are excellent for making edibles or concentrates.
Cannabis is typically trimmed to remove the excess sugar leaves that, while consumable, have a smaller concentration of trichomes than the flower and can be harsh when smoked. Photo by: Gina Coleman/Weedmaps
Begin trimming by holding your colas by a stem and gently cutting away any sugar leaves and stems that surround the buds. This is a very delicate process that requires attention to detail. Ideally, this is done over a screen to collect any trichomes that may break off the plant. Take extreme care when handling your bud. Every moment of contact can result in trichome loss or damage. Whenever possible, hold your plants and branches by the end of the stem.
Wet trim vs. dry trim
While most cultivators trim their cannabis after drying, some prefer to trim while the plant is still wet. When cannabis is trimmed immediately after harvesting, the leaves are still full of chlorophyll, which may lead to a persistent grass-like aroma. Trimming the plant once it has lost most of its moisture is the more traditional approach.
Curing can be considered the final drying stage, allowing bacteria on the surface of the buds to break down any residual chlorophyll and ensuring the colas are neither too moist nor too dry.
This should be a gradual process, as bud that gets too dry will degrade more easily during transportation and packaging, lose potency, and become unnecessarily harsh to smoke. On the other hand, bud that is too wet may grow mold. Preserving fragrance and flavor is a key concern for cannabis cultivators while curing. Overexposure to light, oxygen, and high temperatures can break down cannabinoids and terpenes, and ultimately reduce potency. Striking a delicate balance between dry and moist is the key indicator of a finely cured bud.
Growers should never rush through curing. The process often requires significant trial and error. One to two months is generally a sufficient length of time for curing, though preference and available time to cure may differ among growers. It’s important to keep the environment around your cannabis cool during the curing phase.
This curing process can be performed by placing your trimmed buds in a glass jar or rubbermaid tote for 4-8 weeks. During the first week or two, the containers should be opened daily to allow some fresh oxygen to replace the air in the container. This process is called burping and is repeated until the buds have the optimal moisture content. In the last two weeks of curing the containers are opened every 2-3 days.
Cannabis storage tips
Glass jars are the ideal option for short-term storage. Ideally, cannabis jars should be opaque and airtight for ample preservation of cannabinoids and terpenes. For long-term storage , growers should vacuum seal their final product whenever possible.
Cannabis cultivation is a dedicated practice for home growers and professional cultivators alike. To master growing marijuana takes a lot of patience and trial and error, but with time — and a few great suggestions from seasoned growers — you’ll be able to give your plants a healthy life from seed, or clone, to harvest.
Local cannabis cultivation laws and regulations
In most countries and local jurisdictions where cannabis is legal — medically or recreationally — some sort of home cultivation of marijuana is typically allowed, but growing laws vary significantly from country to country and even city to city. If you’re a prospective or current home grower, you should know the laws and regulations of your jurisdiction.
From seed to harvest, the cannabis plant’s growth cycle can last anywhere from 10 to 26 weeks. Learn more about how to grow marijuana & cannabis cultivation.
The professionalization of cannabis growing
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A commercial medical-cannabis cultivation facility in Moncton, Canada. Credit: Organigram Inc.
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.
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.
“As the industry has gotten bigger, they realized they must transition to use modern horticultural science,” says Youbin Zheng, a horticulture researcher at the University of Guelph, Canada, who works with cannabis companies.
Part of Nature Outlook: Cannabis
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.
“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.”
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.
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.
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.”
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.
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.”
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.
A student inspects a cannabis plant at Niagara College Canada’s teaching laboratory in Niagara-on-the-Lake, Canada. Credit: Niagara College
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.
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.
“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.
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.
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.”
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.”
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.
“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.”
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.
Cannabis analytical labs are becoming more professional. “I’ve seen an evolution in the sophistication of the industry,” Brauninger says. “Most of the people running labs now have PhDs and experience in the pharmaceutical industry. It’s light years more sophisticated than five or six years ago.”
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.
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.
More from Nature Outlooks
Although many small-scale cannabis growers at first questioned the need for intensive product testing, most can now appreciate the benefits that the rules bring to the market. “People see the need for quality control and testing,” says James. “It brings a legitimacy to the industry that hasn’t always been there.”
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.”
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”.
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.”
Nature 572, S10-S11 (2019)
This article is part of Nature Outlook: Cannabis, an editorially independent supplement produced with the financial support of third parties. About this content.
As the wave of legalization advances, a budding industry is adopting the high standards of consumer-product makers to meet regulatory requirements.