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Cannabis Terpene Levels: Indoor Vs Outdoor Grow

Written by Lydia Kariuki

The growing acceptance of cannabis as a therapeutic agent has sparked an interest in the bioactive or healing molecules in the plant, with cannabinoids and terpenes being the locus of the discussion. Consequently, factors affecting the cannabinoid and terpene profile of a strain have been of great significance. A recently concluded study has revealed that cannabis is only as good as the cultivation environment and hence potency will fluctuate based on environmental factors. This reinforces the age-old belief that indeed nurture, and not just nature determines the characteristics of a living thing.

Traditionally,  cannabis has been grown outdoors by local communities and legacy cultivators. But as cannabis has become more mainstream the demand has increased compelling cultivators to explore indoor cultivation that allows for year-round cultivation. Unknowingly and as this study has revealed, the chemical composition of cannabis has undergone significant changes as well.

Details of the Study

A group of researchers from New York’s Columbia University together with the owners of three cannabis companies  – Huckleberry Hill Farms, Moon Made Farms, and Novato’s Cosmic View  –  conducted the study that compared the cannabinoid and terpene profile of cannabis under natural and artificial cultivation environments. The results of the study were published in the journal Molecules in January 2023.

The researchers cultivated six cannabis plants from two genetically identical cultivars:  Red Velvet and Cheetah Piss. Three plants were cultivated outdoors in “living” soil and under natural sunlight while the other three plants were cultivated indoors using artificial light and medium. When the plants were ready for harvest the researchers selected buds of similar size and morphology from the upper third of the plants. Gas chromatography with mass spectrometry (GC-MS) was used to analyze terpenes while ultra-performance liquid chromatography (UPLC-MS) was used to analyze cannabinoids.

Outdoor Cannabis Has Higher Terpene Levels

The researchers found that cannabis that had been grown outdoors had a greater diversity of terpenes which also occurred in higher concentrations. They reported “remarkably higher levels” of the following beneficial terpenes:

  • Limonene

  • Β-myrcene

  • Β-caryophyllene

  • Α-humulene

  • Α-bergamotene

  • Α-guaiene

  • Germacrene B

The research also highlighted a “greater preponderance of sesquiterpenes” in outdoor-grown cannabis. Interestingly, there was only a slight difference between the cannabinoid profiles of indoor cannabis compared to outdoor cannabis. Indoor-grown cannabis had a higher concentration of oxidized and degraded cannabinoids. The researchers elucidated that this could be as a result of lower terpenes levels in the indoor samples; terpenes act as antioxidants. The levels of cannabigerolic acid (CBGA) and cannabidiolic acid (CBDA) were almost similar between the two groups. Cannabichromenic acid (CBCA) was slightly higher in outdoor plants while tetrahydrocannabutolic acid (THCBA), was higher in indoor plants.

Need to Look Deeper Into Outdoor Cultivation

Most commercial producers cultivate cannabis in indoor environments that allow them to manipulate and optimize production. Unfortunately this may result in a less robust terpene profile. With research now highlighting the importance of terpenes in a cultivar,  there’s a need to reimagine and reinvent outdoor cultivation as the next frontier in commercial cannabis production.

About the author

Lydia Kariuki