Ideally, cannabis should be harvested at peak cannabinoid and terpene levels, and then properly dried and cured; however, that can often be easier said than done.
How do you know when it’s time to harvest?
With harvesting, there are few hard and fast rules. Even in today’s mature adult-use markets, cannabis is harvested based solely on observations of a handful of factors, including:
1. 60-day flower period: It’s common industry knowledge that cannabis plants complete the flowering stage in approximately 60 days. Some cultivars require less time and some require more time to reach full maturity, but this rule of thumb is typically the first indicator of when to harvest.
2. Stigma/stigmata color/drying out: A popular belief and observation-based indicator is that once roughly 40 percent of stigmata dry out and turn brown—leaving 60 percent of the stigmata with a white color—your plant is mature and ready to harvest.
3. Gland color: Ranging from clear to milky, and amber to reddish, most discerning growers use gland color as a ripeness indicator. As resin glands form, they typically will be translucent (although some express color). As the plant and the glands mature, the resin glands’ composition changes as cannabinoid and terpene percentages increase. As the plant matures, the clear resin glands typically become opaque. The glands will begin to turn colors, ranging from amber to dark red, as the plant reaches the end of its life cycle. If you wait too long or over-expose those resin glands to light, they can oxidize. Oxidization can darken the color of and degrade cannabinoids.
The objective is to estimate when to harvest based on maturity of a given percentage of resin glands. Some growers harvest when they see 70-percent clear resin glands, 20-percent opaque glands and 10-percent amber/red glands. Some prefer different ratios, seeking desired or preferred cannabinoid content. Those growers might harvest later in the plant’s development, when a larger percentage of glands have become amber or taken on a darker, more mature color. In essence, these growers are altering cannabinoid ratios to suit their specific needs or to elicit a desired effect.
Extractors discovered years ago that if they harvested before the resin glands turned amber or red, the resulting extract had a lighter color without a major compromise in overall THC percentages or noticeably reduced terpene content. Many extractors began to purposely harvest early to avoid darker-colored extracts tainted with colorants (pigments and flavonoids) combined with the dark-colored cannabinoids in the resin gland.
These methods of determining when to harvest cannabis are highly subjective and may be inaccurate. Ideally, cannabis should be harvested only when a chemical analysis reveals that the desired levels of cannabinoids and terpenes have been achieved. Take vintners, for example. Grape growers utilize a Brix meter to analyze grapes’ sugar content, which determines when he picks the them. He is aiming for a targeted sugar percentage. Too much or too little, and he will change the wine’s flavor profile.
Cannabis should be harvested similarly, in that it should only be harvested when production of desired compounds has peaked. As of now, an apparatus to determine cannabinoid or terpene levels in a bud on the plant does not exist. However, given the financial reward such a device would bring to its creator, I suspect we will have one someday.
What is the point of diminishing return with respect to cannabis destined to be extracted, not sold as raw cannabis buds? In other words, at what point in a cultivar’s flowering cycle does that plant slow down cannabinoid and terpene production? At what point is it more advantageous and profitable to harvest because desirable compound production has presumably peaked? Does a cannabis variety only produce lower amounts of compounds in later stages of life? Are the stages for cannabinoid development different or similar for all cultivars?
The implications of these unanswered questions are many. I ask them to illustrate that if the cannabis is destined for extracts, and that THC or CBD production and terpene production is minimized in the late flowering stages, then there is a point at which there are more resources going into the plant in the form of labor, space, electricity, nutrients and water, than compounds being produced. As such, when growing for extraction, it could be advantageous and profitable to harvest (for example) 2 acres of cannabis two weeks early, even if harvesting early resulted in (hypothetically) 10-percent fewer available compounds, if it would facilitate one extra harvest per year. (If a grower is currently getting four cycles per year utilizing an eight-week flowering cycle and cuts each harvest by two weeks, then there is enough time for another six-week flowering cycle in the same calendar year.) Again, the focus of this harvest would be compound production (cannabinoids and terpenes), not biomass (flower/bud).
(Editor’s note: Read more about “Workflow, Turns and Yields” in CBT’s May 2018 Hort How-To Column.)
To verify whether such a practice would be worth the cost, growers must calculate the production cost increases that come from that extra cycle, in addition to calculating the amounts (or diminished amounts) of compounds in relation to a plant’s harvest time. Calculating diminishing return rates turns THC, CBD and all other cannabinoids and terpenes into nothing more than commodities, and that is exactly how they will be viewed by corporations of the future.
Both cannabinoids and terpenes will be viewed as starting material or active ingredients. Many emerging corporations want active ingredients. They do not want to cultivate, extract or process cannabis. They want those active ingredients in an exact percentage or form. Recent market projections in Canada indicate that manufacturers desire to put cannabis into anything that can be ingested, ranging from water to edibles (starting in 2019) to capsules. Manufacturers want active ingredients—not trim, flower nor kief. They do not care what cultivar it is nor which cultivation method was used.
Growers who understand this may view cultivation, harvest and crude extract production from a slightly different perspective. They may choose to produce cultivars that rapidly generate cannabinoids. This would allow them to harvest at week six, seven or whenever production has peaked, allowing them to focus on harvesting the active ingredient through resin-gland separation to efficiently produce crude extract. These resin glands can then be refined and super-refined via distillation into a form desired by manufacturers. The obvious goal would be maximum production of a desired compound with the lowest possible production cost. (Editor’s note: For more on extraction refinement, read the CBT November 2018 print edition's Tomorrow in Cannabis column, “A Crude Awakening.")
Many corporations have recently divulged their intent or interests in entering the legal cannabis market, including household names like Anheuser-Busch InBev SA/NV, PepsiCo and Corona (Constellation Brands)—the latter of which invested US$4 billion in Canada’s Canopy Growth Corporation. Global corporations are establishing themselves primarily in the legal Canadian market with the intent to develop their brands and products for future production and sales to not only Canada, but any market that allows importation. Many are also likely preparing for the emerging legal adult-use market in the U.S.
To produce their intended products, we can assume these corporations will demand the lowest price possible for ingredients, which encourages foreign sourcing. Some corporations intend on sourcing active ingredients from countries such as Colombia, Australia, South Africa, Lesotho, Mexico, Portugal and Uruguay. Odds are, they will source from anywhere they are legally allowed to import with the lowest cost of production.
Some companies will choose to source CBD from hemp cultivated by American farmers to be refined in an industrial or pharmaceutical setting. But in a free- market economy that treats cannabis and its derivatives as agricultural commodities, I suspect it unlikely that corporations would source active ingredients from either Canada or the U.S. The increased labor, power and other costs of North American cannabis production would not compete with those countries mentioned (a semi-skilled worker in Colombia can expect to make $20 per 8-hour workday), which means prices for active ingredients may someday become quite competitive. Once that happens, some producers will be forced to examine how and what they produce.