Most cannabis information available today is based on observations made by underground growers during repeated production cycles over the course of the past several decades. Indeed, prohibition has stifled cannabis research for most of the 20th century. In the near future, however, there will be many legitimate cultivation studies as legalization and legitimacy often come with the ability to scientifically research and examine all aspects of cannabis cultivation practices.

Until those studies are published and shared across academic and cultivation channels, cannabis cultivators are left with dozens of questions, including: Are there other, more productive growing methodologies than what I am currently using? Are there cultivation methods that enhance production of certain cannabinoids or terpenes? Which input has the biggest positive impact on yields and cannabinoid production?

Given the many variables under a cultivator’s influence, it’s good to question your practices today so that you remain ahead of the technology curve tomorrow. Here are six areas in which more information will spur further questions and better solutions.

1. Lighting:

Do we know exactly what light level and spectrum each cultivar prefers in each stage of production?

Is it a fixed spectrum, such as a blue-dominant spectrum in vegetative growth and a red-dominant spectrum in flowering stages, as is commonly believed and accepted as fact by some? Or is it possible the plant prefers a roving spectrum throughout a daylight period so that all spectrums are available throughout the day? Or is it best to mimic nature and utilize blue and red spectrums as many currently do? Conversely, is there a preferred targeted application that yields superior results? Is there a perfect spectrum for every stage of growth? These are the types of questions academic studies and white papers can and should answer.

2. Precise nutrient application and utilization:

I have witnessed clones taken from the same mother plants inexplicably outperform all others clones around it under similar environmental conditions and lighting, and in the same growing media and amendments. The only hypothesis I could drum up was that the plant received exactly what it wanted exactly when it wanted it, whatever “it” is.

Today, reports on nutrient applications are starting to hit the mainstream cannabis market (including in Cannabis Business Times’ “Nutrient Matters” series by researchers at North Carolina State University (NCSU)). These first studies are looking at the low-hanging fruit of cannabis nutrition, namely: What are the specific nutritional requirements of a cannabis plant in each growth stage? Many growers might intuitively know this, but it does not take away from the importance of such studies leading us to a deeper understanding of how this plant works.

Indeed, projects like the NCSU research could help growers determine if we sometimes apply fertilizers or amendments that are not utilized by the plant during specific stages. If it can be shown that cannabis plants only use/absorb/feed on certain elements at certain life stages and completely ignore anything that is not needed, growers can develop more efficient and precise nutrient application systems and methods, which is both environmentally and financially responsible. Deeper analysis into nutrient needs of cannabis plants also might reveal systems, nutrient formulations or amendments that accentuate or accelerate the production of biomass or desirable compounds.

3. pH fluctuation:

Traditionally, cannabis growers prefer a pH range of 5.8 to 6.8. Many choose 6.2 to 6.4, as within this range, they are likely to get most, if not all, of the desired nitrogen, potassium and phosphorus (NPK) minerals, as well as many other essential elements required for healthy plant growth. By raising or lowering the pH of a nutrient solution, it raises or lowers the availability of the required elements.

Is a plant receiving the desired amounts of elements at proper levels when employing this method? Or would it be best to fluctuate the pH? Put differently, would a slight variation in pH from one watering cycle to another improve health, growth and cannabinoid production? If you had a watering cycle that watered plants two to four times a day depending on methods and media, the first application of the day could have a pH of 5.8. The second application could be 6.2, the third could be 6.4 and the fourth could be set at 6.8. Would fluctuating the pH during watering ensure that all NPK elements are fully available throughout the watering cycle? Or would that be ineffective?

4. Temperature fluctuation:

Traditionally, indoor cannabis is produced in a very controlled environment where high and low temperatures are set and closely monitored. Outdoor plants, for their part, are subject to the whims of nature, resulting in wide-ranging daily and seasonal swings in environmental conditions, especially temperature. Outdoor cannabis plants typically flower in late fall, when temperatures are cooler. (Daily light interval (DLI) determines when a cannabis plant will flower, not temperature, but that is not the focus here.)

But what temperature range is best? Should you maintain constant set point temperatures? Or maybe allow for outside temperature fluctuation influences to dictate temperatures to some degree? Not too extreme, but perhaps you should set cooler temperatures in flowering stages and night cycles to mimic daily and seasonal temperature shifts.

Which temperatures are best for cannabinoid production and terpene preservation while maintaining proper humidity and vapor pressure deficit parameters? Cooler temperatures lend themselves to terpene preservation as terpenes evaporate at higher temperatures, yet most cannabis cultivars’ yields suffer if cultivated in cooler environments. There is an obvious balance between healthy and vigorous plants that yield well, produced in warm environments, and plants produced in cold/cooler environments with a primarily focus on terpene production and/or terpene preservation. What temperature is best for compound production and preservation? And what are the parameters?

5. Ethylene Gas:

Besides the factors listed above, there are many influences to investigate that have been utilized for decades by modern agriculture in a multitude of applications. For instance, ethylene gas is utilized to accelerate the maturation of fruits and flowers in some cases. I have seen a grower who used an ethylene gas buildup during the last days of flowering to cause a majority of a plant’s large fan leaves to dry up and fall off, without compromising the product’s quality. Would it be possible to mature cannabis early without compromise of yield, desirable compounds, or quality at scale by elevating ethylene levels?

6. UVB light spectrum levels for THC production:

Millions of dollars already have been spent investigating this one influence. Yet, even when compiled, the resulting studies and research are conflicting. Most published papers indicate there is a significant benefit to using UVB lighting to increase THC production, while investigations by others indicate very little impact.

Other questions remain: How much UVB light spectrum does a cannabis plant prefer? How much is too much? Can UVB have a positive influence on yield? Does UVB aid in control of contaminants such as powdery mildew?

But Wait, There’s More

Many other areas of cannabis production need further investigation. The cannabis plant is responsive to many influences, such as organic natural enzymes like seaweed and other organic inputs.

Plant hormones are another potential production influence that merits further research. Gibberellins are a group of plant hormones that stimulate stem elongation, germination and flowering. Auxin is another plant hormone that is produced in the stem tip and promotes cell elongation and inhibits growth of lateral buds.

All of this is to point out that we don’t know what we don’t know, and I believe a lot of facts about cannabis cultivation and commercial production have yet to be truly established. So, avoid sticking to your guns unless you have research as ammo.

Kenneth Morrow is an author, consultant and owner of Trichome Technologies. Facebook: TrichomeTechnologies Instagram: Trichome Technologies k.trichometechnologies@gmail.com

Air purification is critical to create an ideal environment for an indoor grow. Your facility’s air quality directly affects the environmental systems, integrated pest management and human comfort. With proper design and preventative maintenance, better crop quality can be ensured through reduced pest pressure and best care for environmental control systems. Here are eight tips for proper and efficient air purification.

1. Facilitate proper air movement throughout the growing environment to assist in maintaining optimal temperature and humidity. This is achieved through horizontal air flow and air exchanges. Microclimates within in the crop can create ideal environments for diseases and other pests, so to reduce pest pressure, create air flow that minimizes humidity and heat pockets. Air exchanges move air through the entire room and create an opportunity to purify air. At Pruf Cultivar, a vertically integrated company based in Portland, Ore., we complete 30 air exchanges per hour.

2. Create a multilayer system of filtration. Implement different technologies to reduce the presence of pathogens.

Prefilters: Use passive, lower-cost filters to trap larger particles, which will permit the finer and more expensive filters to work more efficiently and longer. A pleated filter creates a larger surface area, increasing filtration with higher air flow.

Carbon/Charcoal filters: These filters trap passing organic matter and reduce odor.

Excitation technology: This technology uses an electrical field to increase particle collision (excitation), which makes smaller particles stick together to create larger particles, enabling the HVAC filters to remove the resulting, larger particles permanently.

Ionization technology: These systems contain an electrical field and two electrically charged plates—one negatively charged, and one positively charged. As a particle passes through the electrical field, it is ionized and attracted to one of the two plates, removing it from the air stream.

Ultraviolet photocatalytic oxidation (UV-PCO): Using ultraviolet light to energize a catalyst, electrons are released and interact with water in the air stream, creating hydroxyl radicals, which destroy pathogens.

High Efficiency Particulate Air (HEPA) Filters: These remove 99.97 percent of particulates 0.3 microns in size. Spores are 3 to 40 microns in size.

Active airflow along with Integrated Pest Management (IPM) throughout the grow and surrounding areas can aid in your efforts to keep pathogens out of the air and maintain a clean facility from top to bottom. These tips can help.

3. Filter air throughout the whole facility to reduce pathogens and odors. This ensures people’s safety and comfort while reducing pest pressure.

4. Place foot baths/mats strategically throughout the grow to reduce tracking pathogens from outside to inside or from one grow environment to another.

5. Create a “uniform” and wear freshly laundered clothes into grow rooms every day.

6. Keep tools used in other gardens from entering the grow. Grow tools should be used, cleaned and stored at the grow.

7. Preventative maintenance should be completed successfully and in a timely fashion to ensure proper air filtration and that other environmental control systems work correctly.

8. All team members should participate in IPM and voice concerns and ideas for improvement.

Lee Nye is the head grower at Pruf Cultivar. She has a Bachelor of Science in Plant Biology, and previously was a grower at Pleasant View Gardens and D.S. Cole Growers nursery for a combined 15 years.

One of the first questions I ask a potential consulting client is, “Do you and your employees purchase and consume the cannabis you produce? And if so, are you proud of the products you produce?” The answers I get sometimes surprise me, especially when the answer is “no” and that it does not matter because their products sell, regardless. At those times, I politely decline the employment opportunity. At no time in my career have I had any desire to produce anything other than the absolute best-quality cannabis possible with the funding and situation presented. I always strive to do the best I can with what I have.

A Colorado grower had once asked me to do a facility evaluation because their production totals were getting lower and lower each month. I began my assessment with a quick tour of the facility, then re-walked the facility without management, which allowed me to interview staff about their thoughts as to why production was slipping. Each employee sheepishly explained that management did not listen to the input or the needs of the employees, and that management told the grower that the plan was dictated by costs. Two out of three members of management never consumed cannabis, and it was simply a commodity to them. They were more concerned with the completion of their dispensary remodel than with the quality of their cannabis.

At one point, I attempted to explain to the carpenter/owner that no healthy cannabis plant is completely yellow and that he had 200 yellow plants. He would not even entertain me to go look at them.

At the same facility, another owner walked me to their drying room. As soon as they opened the door, I was blasted with the overwhelming odor of ammonia, a byproduct of degradation caused by inadequate airflow and by placing freshly cut product in the same environment with material that was almost dry. This essentially rehydrates the almost-dry material and does not properly address the humidity levels. Freshly cut material cannot be placed in the same room with material that has been drying for multiple days and be expected to dry at a uniform rate without proper ventilation, humidity and temperature control.

Yet again, these owners did not care because the product still sold. The one owner who did consume cannabis, as well as all their employees who were consumers, did not consume the cannabis they produce, nor were they proud of the product they sell.

A Phoenix, Ariz., operation was so focused on filling up its 65,000-square-foot facility to make money that it completely neglected to construct a proper drying and curing area. The management didn't understand or care about the importance of drying and curing. After three years of operation, their head grower quit. They couldn't sell all the mid-grade product at their two dispensaries, so they were forced to wholesale the majority of what they grow to competing dispensaries.

They do not grow quality cannabis, and theirs is certainly not a product to be proud of. When competitors produce superior products for a superior price, a company built on inferior cannabis will ultimately implode. You can grow the best, strongest, most aromatic cannabis in the world, only to destroy most of those qualities with improper drying and curing.

The Art of Drying and Curing

Drying and curing cannabis properly is an art in itself. Similarly, a tobacco farmer who grows tobacco for the finest hand-rolled cigars gives the highest level of care and attention to detail when drying and curing, which sets the stage for the final product. I have been to organic tobacco farms on a Caribbean island that dry and cure their leaves by old-world standards, the same as they have for decades. The care and the attention to detail they demonstrate is all for the love of the art, not just for monetary gain.

In the California, Oregon or Washington state coastal regions, it is very difficult to rapidly dry or over-dry cannabis because of the marine layer influence, which causes elevated nighttime humidity and, in some areas, fog. It is this marine layer influence that is responsible for mold and/or mildew proliferation in some cannabis. To rapidly dry or over-dry cannabis in these regions, one would have to try in fall and winter.

This is not so in some areas of Nevada, Arizona or Colorado, two of which have significant differences in elevation, temperatures and humidity variation. Arizona and Nevada are both different climates that can range from 115°F in summer to 28°F and lower in winter, with low humidity levels most of the year and no real humidity influence except for monsoon season in Arizona.

Denver, Colo., is more than 5,000 feet in elevation and in many areas, elevation is even higher, and temperatures can range from sub-0°F in winter to well over 100°F in summer. In winter, in one 24-hour period, it can range from subzero and snowing with 0-percent humidity at night to 75°F with 60-percent humidity during the midday as the snow melts in the sunshine. Both of these diverse climates require special attention to drying and curing, which may not be required in a region that has a predictable coastal marine layer influence.

A bud of cannabis should have some give-and-take to it when squeezed, similar to the give-and-take when squeezing a marshmallow between thumb and forefinger. The bud should not be so dry that it simply crumbles or turns to a dry powder. Rapidly dried or over-dried cannabis, as mentioned, has diminished levels of desirable terpenes and is much less flavorful than properly dried and cured cannabis. Small amounts of cannabis are fairly simple to dry and cure, as long as you understand the nuances and maintain a stable proper environment that is not too hot nor too cold, in a well-ventilated area.

However, large commercial amounts of cannabis require special attention to every detail to ensure the resulting product is superior in quality, not over-dried and flavorless. Many believe that with properly dried and cured cannabis buds, the primary stem inside the body should be so dry that it snaps in half when bent. In reality, that would be considered over-dried. It should crack, yet bend without being wet or excessively moist. Again, the stem should audibly crack, but not break in half, and the bud should have give-and-take, not explode into powder.

It is a fine line. Drying and curing are developed skills that come from actually consuming the cannabis you produce (if you are a medical patient or involved in an adult use business) and striving to always make it better. Yet again, it is an art as well. There is no magic temperature and humidity set point, because there are many variables from seasonal temperatures, fluctuating humidity levels, elevations, barometric pressures, different cultivars and quantities, and so on.

However, a drying room should always be properly ventilated, with fresh, filtered, outside air and with proper odor control practices on all exhausted air. It should have the ability to both impart humidity via a humidifier and to dehumidify via a dehumidifier, as well as the ability to both heat and cool. Whether you hang dry individual plants or branches with buds attached or put wet, trimmed buds on racked screens, whether your crop is 500 pounds or 50,000 pounds, you must have at least that amount of control over the drying rate—not excessively hot (over 75°F to 80°F). Many dry at lower temperatures, for example, 60°F to 70°F, to preserve the highest percentage of terpenes possible.

Temperatures that are too cold, however, with improper airflow, will produce inferior cannabis with undesirable qualities; the final product retains excessive levels of chlorophyll, and never smells or tastes as it should, and sometimes has a fresh cut grass or hay odor. Humidity control is always a must. Logically, one would want to eliminate as much humidity as rapidly as possible, which is typically accelerated with elevated temperatures. But there is a fine line between rapidly drying the cannabis and rapidly evaporating terpenes, contained inside the trichomes that coat the outside of the cannabis buds.

Each and every terpene has a boiling point and temperature at which it begins to evaporate. Monoterpenes evaporate first and are typically the primary terpenes evaporated in drying. The task is to eliminate unwanted moisture from the plants and buds as rapidly as possible without evaporating excessive amounts of terpenes. The outside of the bud dries first and becomes slightly dry to the touch.

The art is to draw the inner core humidity to the outside slowly, without sacrificing terpenes. The cigar tobacco-leaf drying sheds on the Caribbean island had ropes hanging from the ceiling. Bundles of leaves were raised or lowered from the floor to the 20-foot ceiling multiple times a day to accommodate proper drying and curing, because the higher you go in the shed, the hotter and more humid the air. Take note, this is in the Caribbean on an archipelago in the Atlantic Ocean with a hurricane season.

Heaters, coolers, humidifiers and dehumidifiers combined with airflow are the science if used properly, but there must be “the art” in the equation as well. Someone who does not appreciate the nuances of cannabis and all its qualities, whether they personally consume cannabis or not, should not be in charge of drying and curing.

When the outside of the plant is dry, it is best to rehydrate the outside of the bud by drawing the inside moisture to it. The best way to achieve this is to place the buds into a sealed container for a short period at drying temperature (for 2 to 24 hours depending on quantity), while periodically exchanging the container air. The bud will again become uniform in moisture consistency or dryness. This can be very time-consuming and difficult at large-scale, which is why few large-scale commercial growers do it. The homogenized buds are then rehung or placed back on drying racks to repeat the process until the desired moisture content is achieved, which should never be “very dry.”

This begins the curing phase. Always be careful to avoid excessive temperatures and be vigilant for any possible signs of mold. If there is any mold present, it will spread in a warm, moist environment, which is exactly what you don't want. Properly dried cannabis is fairly easy to cure. After proper drying, the cannabis is again placed into sealed containers to prevent moisture and terpene dissipation. The sealed containers are checked multiple times a day, and all air in the container is exchanged for fresh air.

At this point, proper moisture content is closely monitored. If a container is opened and the buds are excessively moist, the container is left open until desired moisture content is achieved, or the contents can be placed on the drying rack and closely monitored.

This process is repeated over and over and over again until the perfect, uniform, desired humidity and moisture content are achieved. And therein lies the art.

Prices for greenhouse and outdoor flower deteriorated dramatically in 2018 after a bounteous fall harvest in 2017. Meanwhile, indoor product saw significantly smaller declines in wholesale rates last year, according to data collected by Cannabis Benchmarks.

National quarterly prices in 2018 illustrated the large supplies of greenhouse and outdoor product available in legal cannabis markets. National volume-weighted price for greenhouse products averaged $1,192 per pound in Q1 2018. That dropped by 12 percent to $1,047 per pound in Q2, then fell another 10 percent to $946 per pound in Q3. Outdoor flower saw its going rate average $938 per pound in Q1. It sank 21 percent to $740 per pound in the second quarter, before sliding an additional 6 percent in Q3, to $693 per pound. Both types of sun-grown product saw rates level off in Q4, when greenhouse and outdoor flower averaged $942 and $705 per pound, respectively.

Overall in 2018, annual average prices for greenhouse and outdoor flower saw respective declines of 29 percent and 30 percent compared to 2017’s wholesale averages. The downturns outpaced those of the annual average for indoor flower, which decreased 17 percent in 2018.

Additionally, while rates for indoor product dropped overall last year, weekly prices were observed to stabilize, and in some cases rise, around periods of strong demand (4/20, Labor Day weekend, and the end-of-year holidays). Quarterly prices increased for indoor flower in Q2 and Q4, which was largely due to elevated rates in April and December, respectively. Wholesale rates for greenhouse and outdoor product generally saw little to no respite from their downward trends even when buyers were looking to take in additional supply.

Prices for indoor and greenhouse flower recovered somewhat during Q1 2019. The average prices for both grow types in Q1 2019 were up roughly 3 percent relative to Q4 2018. Meanwhile, outdoor flower’s quarterly average rate for Q1 of this year was down by more than 5 percent from Q4 2018, as another year of good growing conditions on the West Coast led to robust harvests that piled even more inventory onto already ample supplies.

At the end of Q1, national rates for indoor and greenhouse product were up a bit compared to Q4 2018, while the price for outdoor flower has tracked downward slightly.

Adam Koh is the editorial director for Cannabis Benchmarks.