Is indoor-grown cannabis (really) of superior quality than outdoor-grown?
Why in the world would an energy and climate researcher (me) be posting about the relative “quality” of indoor- versus outdoor-grown cannabis?
Some argue that energy-intensive indoor cultivation is superior to open-field cultivation and, indeed, in some sense “essential” for humanity. It’s an important question (to me, anyway) because it is usually the first reason given for why cannabis “needs to be” grown in energy-intensive indoor factory farms…
In practice, there are competing beliefs and positions on the issue, and of course the definition of quality itself varies depending on what one values or is trying to achieve. Some may look at the type and proportions of terpines or the quantity of THC (potency) as indicators of quality. Attributes like appearance, aroma, and taste are more subjective. Indoor cultivation aims for standardization and replicability, yet some connoisseurs say the year-to-year variations characteristic of outdoor cultivation are actually of interest (think wine vintages). Others associate quality with “cultural” factors such as appelation and who the growers are.
Indoor growers of course insist that their product is hands-down superior and that there should be no further discussion about it. Outdoor growers typically have a contrary view. There is clearly potential for apparent if not actual bias in both cases — so, what kind of independent data do we have that is also immune from the “lab shopping” or other bias that may occur in the industry?
A rare set of side-by-side results by Gomez et al. (2022)— covering five strains each grown outdoors and indoors by MCR Labs, apparently in Massachusetts or Pennsylvania — found that outdoor-grown plants almost universally had better terpenes and CBD profiles, and even higher THC levels than their outdoor sisters (see chart at end). One of the strains had measurable cadmium levels (a heavy metal) indoors, but none outdoors. These and other authors comment strain choice has a more central role in “quality” than cultivation method. Results vary quite dramatically by strain.
This was corroborated in another study, skillfully sumarized by Nate Seltenrich, where researchers at Columbia University and three cultivators found that outdoor-grown cannabis had a wider variety of cannabinoid and terpenes and higher levels of these and other active ingredients compared to genetically identical indoor-grown plants. Full report here. Additional support is found in the study by Zandkarimi et al. (2023).
Many San Francisco Bay Area cannabis luminaries were quoted back in 2011 as saying there was no material difference:
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Kevin Reed, who owns Green Cross cannabis dispensary said: “If cultivated correctly and with care, there should be no difference between the same strain grown in- or outdoors.”
Erich Pearson, CEO of the San Francisco Patient and Resource Center (SPARC) dispensary and sat on San Francisco’s Medical Cannabis Task Force said: “There’s a misconception out there that indoor is better marijuana than outdoor, but we don’t think that’s true.”
David Goldman, who is faculty at Oaksterdam University, is active in California NORML and the San Francisco chapter of the California Growers Association, and formerly served on San Francisco’s Medical Cannabis Task Force said: “I’ve seen outdoor that can compete with the best indoor strains. …I would match the best outdoor I know up with anybody’s indoor, any day.”
Rick Pfrommer, former purchasing manager for Oakland’s Harborside Health Center, said: “We’re starting to find [outdoor] strains that were scoring just as high as indoor.”
And, Berto Torres, chief operating officer of GFarma Labs, a cultivation company producing both indoor (greenhouse) and outdoor cannabis, operating in California, Washington state, Oregon and Nevada says there is a level playing field. “You have guys doing outdoor that will rival indoor in potency, and greenhouse, forget about it, (the high potency is already) there.”
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One thing suggested by these quotes is that it’s critical to be clear as to whether one is comparing typical or best practices. Otherwise, products and practices can be cherry-picked to make a desired point. Arguably, what matters in this discussion are best practices.
When it comes to the recreational uses of THC, some focused outdoor growers are reaching well into the 20% (5-times the potency of mainstream 1990s pot), while the very most potent indoor-grown reaches above 30%. That said, one has to ask what kind of imposition it is to have to smoke 1.5 hits of good outdoor to get the same effect as 1.0 hits of good indoor at 35% THC. It’s kind of like saying White Lightning moonshine is “higher quality” than Stolichnaya Vodka. Indeed, multiple peer-reviewed studies across multiple countries have found that negative consequences of cannabis use (psychosis) are correlated to potency [here, here, and here]. Further muddying the water, potency claims are often seriously fudged. I would wager that this practice is more out of control for indoor-grown.
Things surely get more complicated when one turns to cannabinoids that may be important for medical applications. I see many references to equivalent or superior cannabinoid profiles for sungrown, and the above-mentioned test-lab studies found that as well. It’s also interesting/puzzling that one of the above-referenced found a significant decline in CBDs between the mid 1990s and the mid 2010s, which may or may not be correlated with the strong shift towards indoor cultivation during that time-frame. In any case, it’s hard to imagine that no one received medical (or recreational) benefits from cannabis for 5000 years before the 1000-watt HPS lamp was invented.
The notion of quality certainly extends to appearance and perhaps “bouquet” as experienced by the nose — although there are even split opinions on that — in which case it’s particularly worth asking whether it is worth it, given the relatively great environmental impacts of indoor cultivation. It is also important to recognize that much more “R&D” has gone into standardizing the aesthetics of indoor flower. That said, photos of prize-winning outdoor bud are rather compelling, and when grown in unconditioned hoop houses I imagine that there are distinct benefits to physical appearance without the energy penalty. Meanwhile the results from Punja et al. (2019) regarding mold forming on buds in indoor grows is certainly a buzzkill.
The importance of cosmetics is decreasing as a more and more flower is diverted for the production of extracts, edibles, and “pre-rolls”.
It is important to think about the ultimate use of the flower (as-is vs extracted). Especially given current over-supply, I imagine that some “perfectly good” flower ends up being processed for oil and blended with that from multiple cultivars. Thus, at a minimum, it would be prudent to cultivate no more flower indoors than is actually “needed”. (Compounding the issue on the energy side, the oversupply is leading to extensive refrigeration, further inflating the carbon footprint.)
Even for those not convinced that outdoor-grown is superior, in a warming world we all need to ask what level of incremental creature comforts are worth further melting the icecaps and whether embodied carbon should itself be included in the definition of quality.
Perhaps the industry is coming to its senses on its own terms. It’s notable that some of the very large actors (e.g. Canopy Growth) have been shuttering millions of square feet of indoor facilities (including greenhouses) and shifting more towards outdoor cultivation. Maybe they are only serving the vape market, but they’re not the only ones seeing a crumbling business case for indoor cultivation. One can anticipate huge swaths of vacant warehouses and lots of stranded investment in some areas, which stands to worsen urban blight and such.
