Study Reveals Chemical Differences in Indoor and Sungrown Cannabis

“The outdoor samples were stickier to the touch and were much more pungent than the indoor samples.”

Scientist woman indicates the chromatogram of mass spectrometry analysis results of compounds, as shown on the computer monitor of mass spectrometer instrument in the laboratory for indoor vs outdoor cannabis study
Photo: S. Singha / Shutterstock

When it comes to cannabis, most people assume the plant’s genetics are primarily responsible for an individual cultivar’s cannabinoid and terpene content. However, it turns out that cultivation practices may also play a significant role.

A recent study published in the journal Molecules reveals how the growing process can impact the cannabis plant. A team from Colombia University, in conjunction with farmers in the famed Emerald Triangle, compared two genetically-identical strains—Red Velvet and Cheetah Piss—grown indoors and outdoors.


The clones were from the same mother plants with the outdoor samples,
“grown in raised beds using a proprietary mixture of all-natural soil and composts under full sunlight.” The indoor samples were grown under artificial light in a proprietary growth medium.

Once the plants reached maturity, the team noticed immediate differences in the look and scent of the samples. As the report states, “the outdoor samples were stickier to the touch and were much more pungent than the indoor samples.”

Researchers then used gas/liquid chromatography and mass spectrometry to examine the cannabinoid content and terpene profiles of each sample. The results showed a remarkable difference between sungrown and indoor-grown cannabis, with the outdoor samples testing higher for several terpenes and showing fewer signs of oxidation and degradation.

The study is a concrete argument for consumers to consider buying outdoor bud, which is often viewed as less desirable.

“The findings were very compelling from a scientific perspective,” said Christine Skibola, Ph.D., a scientist and co-owner of A Cosmic View, which utilizes sungrown flower in its finished goods. “Sungrown cannabis has been looked upon by many in the industry as of inferior quality compared to indoor grown. This has never made sense to me, especially coming from a farming family. Does a tomato taste better grown in your garden under the sun or from a greenhouse-grown hydroponically?”

Sesquiterpenes have a higher prevalence in outdoor cannabis

One of the most intriguing results of the study was the difference in terpene content between the outdoor and indoor flower. The sungrown samples had more sesquiterpenes, a type of terpene with large molecular structures. The terpenes β-caryophyllene, α-humulene, α-bergamotene, α-guaiene, and germacrene B were far more prevelant in the sungrown flower. The farmers attribute the findings to the environment and the behavior of the plants themselves, which express terpenes to help improve the life cycle.

“If a higher level of sesquiterpenes is found in sungrown samples, this correlates to the plant’s environment and the reason the plants produce terpenes: to protect themselves from the natural environment,” said Tina Gordon, owner of Moon Made Farms.

“This includes all aspects of weather, soil type, microorganisms, and the living context the plant experiences,” said Gordon. “So it stands to figure that a plant grown within an infinite number of daily variables will have a more complex defense system than one grown in a controlled environment where there are limited variables.”

Johnny Casali, the owner of Huckleberry Hill Farms and cultivator for the study, agreed.

“With indoor cannabis, you have a consistent temperature, night and day,” he said. “Outdoor cannabis is subjected to all the different elements that nature has provided. The sesquiterpenes—which are heavier terpenes—that have been subjected to nature’s elements are preserved longer.”

Oxidized and degraded cannabinoids raise red flags

The other remarkable result from the study was the condition of the indoor flower. The samples grown under artificial light had high levels of oxidized and degraded cannabinoids.

As Skibola explains, terpenes protect against oxidation, and if those compounds are less prevalent, the likelihood of degradation increases. She believes that the lack of terpene production may be due to a lower presence of natural pests, which terpenes protect against.

“The greater presence of terpenes in the outdoor-grown cannabis likely provides an oxidation shield for the cannabis and that may be why we’re seeing less degradation in the sungrown cannabis,” Skibola said. “Terpenes can also act as natural pesticides. It only makes sense that in a controlled indoor environment, pests would be less of a problem for the health of the plant so terpene production would be lower than in plants grown outdoors.”

The study’s authors raised concerns about the indoor cannabis samples. Colin Nuckolls, Ph.D., a professor of chemistry at Columbia University and lead author of the study, noted that several of the oxidized and degraded cannabinoids may have “adverse or unknown” effects, and that consumers should be aware of the entire chemical profile of their pot.

“We found there was a lot of CBNA and other oxidation products in the indoor cannabis,” Professor Nuckolls said. “It also seemed like there was a lot of degradation going on in those samples. Those oxidation products could potentially have some bad indications.”

Paper reignites debate over testing in cannabis

The study concluded with a call to action for regulators, citing the need for more advanced testing. Many of the compounds found during the analyzing process are not part of the required certificate of analysis testing in California, specifically many of the sesquiterpenes, THCA derivatives, and the degradation products like CBNA.

Casali believes more in-depth analysis would benefit the consumer, and help them make informed choices when shopping for cannabis products.

“The more information that we can give them, the better off they’ll be,” he said.

Skibola hesitated to endorse more stringent lab testing, pointing to the potential costs that would likely fall on farmers who are already struggling to make ends meet. She was more hopeful that the study results would raise the profile of sungrown cannabis, and potentially lead to further examination.

“I hope this research begins to raise awareness and helps to break the long-held myth that sungrown is inferior to indoor grown cannabis,” Skibola said. “Sungrown flower has been looked down upon for so long without any scientific evidence to back it up and now we’re seeing evidence to the contrary.”

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