Above Sea Level: The Unique Benefits of High-Altitude Cannabis Farming

The Effects of High Altitude on Cannabis Secondary Metabolites

Several studies have reported that environmental and genetic factors regulate cannabinoid production in Cannabis sativa L. (Haney and Kutscheid, 1973; Latta and Eaton, 1975; Tuner et al., 1982).

In tropical high-altitude environments, biologically effective ultraviolet (UV)-B (UV-B 280-320 nm) may be linked to greater production of secondary metabolites, such as flavonoids (Caldwell et al., 1983; Flint et al., 1985).

Most notably, Doorenbos and collaborators (1971) have mentioned that cannabinoids may function as solar screens, protecting vulnerable plant tissues from UV-B rays.

Solar UV radiation increases with altitude mainly due to decreasing amounts of air molecules, ozone, aerosols, and clouds in the atmosphere as well as due to snow covered surfaces (Schmucki and Philipona, 2002). With increasing altitude less atmosphere is available to absorb UV radiation. With every 1000 m increase in altitude, UV levels increase by approximately 10% (World Health Organization, 2016). Furthermore, the closer the proximity to the equator, the higher the UV radiation levels. At latitudes closer to the equator, the sun's rays travel shorter distances through the atmosphere and therefore less harmful UV radiation can be absorbed.

The relationship between altitude and Cannabis Secondary Metabolite production has been previously reported. Mountain-grown cannabis had 32% more CBDA, 39% CBGA and 63% CBCA compared to cannabis grown in plains in studies by Giupponi et al. (2020). Higher tetrahydrocannabinol (Δ⁹-THC) levels were found in plants grown in high UV-B environments in studies by Pate (1983) and later in controlled environment studies by Fairbairn and Liebermann (1974). Indeed, the highest UV-B dose tested resulted in a 32% increase in Δ⁹-THC content in studies by Lydon et al. (1987). Despite linear Δ⁹-THC response to elevated UV-B irradiance, Lydon and collaborators (1987) did not find a significant effect of UV-B light on other cannabinoids, physiology and morphology in the drug cannabis chemotype. Interestingly enough, Lydon et al. (1987) suggested that the UV-B absorbing cannabinoids may be important in preventing UV-induced damage to reproductive organs. Therefore, it is probable that populations of Cannabis Sativa L. which express UV-B-enhanced cannabinoid production may have more reproductive success in high UV-B radiation environments.

In more recent studies, conducted in indoor facilities, supplemental UV radiation resulted in a reduced harvest index by 1.6% and no effect from UV radiation on the production of secondary metabolites. Nevertheless, cannabis inflorescence yield and THCA content increased by 66% and 20% respectively when light intensity was increased from 350 to 1400 μmol m-2 s-1 (Llewellyn et al., 2022). Similar findings were reported in controlled environment studies by Westmoreland et al. (2023) where cannabinoid concentration was 3 to 13% higher than the control in UV-treated plants, but the effect was not statistically significant. Studies by Rodriguez-Morrison et al. (2021) that also evaluated UV Radiation Effects on Cannabis agree with the above findings. Therefore, one may consider that the effects of light intensity may have a greater effect on secondary metabolite content when compared to UV radiation alone. More research may be needed to clarify the effects of light intensity and UV radiation on secondary metabolite production in cannabis.

Enhancing Terpene Profiles with High-Altitude Cultivation

Giupponi and collaborators (2020) reported that plants grown at an altitude (1200 m above sea level) exhibited a higher total amount of terpenes when compared with plains (130 m above sea level) counterparts, accumulating more β-Myrcene, trans-Caryophyllene and α-Humulene. Two of the 4 tested high-altitude sites had up to 72% greater total monoterpene content compared to low-altitude sites. Whereas on average across all sites mountain cannabis inflorescence samples had 50% more total monoterpene content when compared to samples taken from plains. A similar trend was observed with sesquiterpenes where one mountain site had up to 75% higher total sesquiterpene content. While the average total sesquiterpene content was 48% greater in the mountain samples compared to the ones collected from plain sites. Isoprenoid flavones (Cannaflavins A, B, and C) were correspondingly upregulated in mountain samples, while apigenin turned out to be more abundant in plains samples. Nevertheless, high light intensity was associated 20% decline in total terpene content (Llewellyn et al., 2022). Indicating that both high cannabinoid potency and terpene content may be a challenging target for cannabis cultivators.

Navigating the Challenges of High-Altitude Cannabis Cultivation

High Altitude Cannabis Cultivation has its challenges including but not limited to high winds, unpredictable precipitation cycles, higher light intensity, longer light exposure and temperature swings. Nevertheless, high-altitude-grown cannabis plants make adjustments to the aforementioned conditions by growing shorter, stronger stems, and lighter-coloured thinner leaves.

The choice of genetics for high-altitude cultivation should factor in aspects such as disease resistance, drought tolerance and performance in cooler temperatures with shorter growing seasons. Since maturity in cooler high-altitude climates may be delayed, close attention shall be paid to trichome development for optimal harvest timing.

Sustainable High-Altitude Farming Practices for Cannabis

Despite of benefits of UV exposure and high solar radiation shading plants from excessive UV and high light intensity exposure may prevent sunburn and may facilitate optimal plant growth and development. Shortwave solar radiation increases with altitude whereas air temperatures tend to decrease (Gale, 1972a; Gale 1972b). Importantly, for many hours during the day, plants may be exposed to solar radiation that greatly exceeds saturation levels for photosynthesis.

Fertigation Strategies for High-Altitude Cannabis Farms

Considerations should be given to greater irrigation requirements due to increased wind velocity and transpiration rates at high altitudes. High transpiration rates of high-altitude grown plants were previously reported in studies by Cohen et al. (1981). Therefore, fertigation should be tailored to weather conditions and nutrient absorption rates to meet mineral nutrition and water demands. Indeed, when access to moisture is not limited at an elevation of 1000 m above sea level transpiration rates may be doubled (Gale, 2004). Explore our article Generative Steering in Cannabis Cultivation: The New Frontier to further advance your cannabis cultivation practices.

When producing cannabis in greenhouses for highly regulated markets the importance of preventative pest and disease control measures should not be underestimated. The ability to repeatedly sanitize production equipment and greenhouse infrastructure and maintain robust barriers to pest entry should be of paramount importance.

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Further Reading:

Doorenbos, N. J., P. S. Fetterman, M. M. Quimby and C. E. Turner (1971) Cultivation, extraction and analysis of Cannabis sativa L. Ann. N. Y. Acad. Sci. 191, 3-12.
Caldwell, M. M., R. Robberecht and D. Flint. (1983) Internal filters: Prospects for UV-acclimation in higher plants. Physiol. Plant. 58, 445-450.
Cohen, S.S., Gale, J., Poljakoff-Mayber, A., Shmida, A., Suraqui, S. (1981) Transpiration and the radiation climate of the leaf on Mt. Hermon: a Mediterranean mountain. Journal of Ecology 69: 391–403.
Fairbairn, J. W. and T. A. Liebmann (1974) The cannabinoid content of Cannabis sativa L. grown in England. J. Pharm. Pharmac. 26, 413-419.
Flint, S. D., P. W. Jordan and M. M. Caldwell (1985) Plant protective response to enhanced UV-B radiation under field conditions: Leaf optical properties and photosynthesis. Photochem. Photobiol. 41, 95-99.
Gale, J. (2004) Plants and Altitude - Revisited. Annals of Botany 94:199.
Gale, J. (1972a) The availability of carbon dioxide for photosynthesis at high altitudes: theoretical considerations. Ecology 53: 494–497.
Gale, J. (1972b) Elevation and transpiration. Some theoretical considerations, with special reference to Mediterranean type climates. Journal of Applied Ecology 9: 691–702.
Giupponi L., Leoni, V., Pavlovic, R., Giorgi, A. (2020) Influence of Altitude on Phytochemical Composition of Hemp Inflorescence: A Metabolomic Approach. Molecules. 25(6):1381. doi: 10.3390/molecules25061381. PMID: 32197420; PMCID: PMC7144370.
Haney, A. and B. B. Kutscheid. (1973) Quantitative variations in the chemical constituents of marihuana from stands of naturalized Cannabis sativa L. in Eastcentral Illinois. Econ. Bot. 27, 193-203.
Latta, R. P. and B. J. Eaton. (1975) Season fluctuations in cannabinoid content of Kansas marijuana. Econ. Bot. 29, 153-166.
Lydon, J., Teramura, A. H., and Coffman, B. (1987) UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES. Photochemistry and photobiology. Volume 46, Issue 2.
Llewellyn, D., Golem, S., Foley, E., Dinka, S., Jones, A.M.P., and Zheng, Y. (2022) Indoor grown cannabis yield increased proportionally with light intensity, but ultraviolet radiation did not affect yield or cannabinoid content. Front. Plant Sci. 13:974018. doi: 10.3389/fpls.2022.974018
Pate, D. W. (1983) Possible role of ultraviolet radiation in evolution of Cannabis chemotypes. Econ. Bot. 37, 396-405.
Rodriguez-Morrison, V., Llewellyn, D. and Zheng, Y. (2021) Cannabis Inflorescence Yield and Cannabinoid Concentration Are Not Increased With Exposure to Short Wavelength Ultraviolet-B Radiation. Front. Plant Sci. 12:725078. doi: 10.3389/fpls.2021.725078
Schmucki, D. A. and Philipona, R. (2002) "Ultraviolet radiation in the Alps: the altitude effect," Optical Engineering 41(12), https://doi.org/10.1117/1.1516820
Turner, C. E., H. N. Elsohly and G. S. Lewis. (1982) Constituents of Cannabis sativa L., XX: The cannabinoid content of Mexican variants grown in Mexico and Mississipi, United States of America. Bull. Narc. 34, 45-59.
Westmoreland, F.M., Kusuma, P., and Bugbee, B. (2023) Elevated UV photon fluxes minimally affected cannabinoid concentration in a high-CBD cultivar. Front. Plant Sci. 14:1220585. doi: 10.3389/fpls.2023.1220585
World Health Organization (2016) https://www.who.int/news-room/questions-and-answers/item/radiation-ultraviolet-(uv)

Above Sea Level: The Unique Benefits of High-Altitude Cannabis Farming

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