How Important is Leaf Temperature in the Grow Room?

Written by Robert Hammell

As cannabis grow configurations become more and more sophisticated, it is increasingly possible to control a variety of factors that contribute to the final product. Light exposure, soil composition, atmospheric conditions all pay a role, but how significant is temperature? Multiple studies have been conducted to determine just how important temperature is to cannabis growth.


Why Temperature Matters

All plants need three basic components for effective photosynthesis: water, carbon dioxide, and sunlight. Temperature not only affects the humidity of the environment, which can lead to more or less water available, but it can also play a role in how much light is exposed. A 1995 study in the Netherlands found a linear correlation between stem and leaf growth when compared to temperature.[1] Temperature change effected 98.6% of leaf growth and contributed to 90% of light absorption per plant.


Exploring Cannabis Temperatures

Leaf development can start below 10 degrees Celsius, but this is not ideal for cannabis growth. When comparing photosynthesis rates at 20, 25, 30, 35 and 40 degrees Celsius, one University of Mississippi study found the rates rise with temperature respectively: 32%, 41%, 44% 50%, and 57%.[2] With higher photosynthesis stimulation, there is a potential for higher biomass yields, but this does not give the complete picture. When temperatures rise too high, there are other concerns that may arise beyond photosynthesis. Excessive heat may also limit plant growth in other ways. A Journal of Cannabis Research study tested cannabis’s resilience by exposing plants to extreme conditions, including exposure of 45-50 degrees Celsius, for 5-7 days.[3] The study found major drops in both THC and CBD production following extreme heat exposure. Even more concerning though is the large drop in cannabinoid production associated with drought stress. Dehydration can lead to as much as 80% less CBD and an 85% drop in THC. Higher temperatures could also contribute to drought stress through increased evaporation.


The Ideal Temperature for Cannabis Growth

Temperature is one variable in the balanced equation to successful cannabis growth. It is possible to grow cannabis successfully outside the common temperature range, but only by adjusting other variables like water, carbon dioxide, and soil composition. The ideal leaf temperature for growing cannabis ranges somewhere between 22-25 degrees Celsius.[4] Anything beyond that will require continued adjustment and monitoring of the cannabis plant.


Image Reference




1- WERF, H. M. G. V. D., BROUWER, K., WIJLHUIZEN, M., & WITHAGEN, J. C. M. (1995, June). The effect of temperature on leaf appearance and canopy establishment in fibre hemp (Cannabis sativa L.). Annals of Applied Biology, 126(3), 551–561. https://doi.org/10.1111/j.1744-7348.1995.tb05389.x


2- Chandra, S., Lata, H., Khan, I. A., & Elsohly, M. A. (2007, October). Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Retrieved September 11, 2022, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/pdf/12298_2008_Article_27.pdf


3- Park, S. (2022, January 4). Effects of short-term environmental stresses on the onset of cannabinoid production in young immature flowers of industrial hemp (Cannabis sativa L.) – Journal of Cannabis Research. BioMed Central. Retrieved September 11, 2022, from https://jcannabisresearch.biomedcentral.com/articles/10.1186/s42238-021-00111-y


4- Sabeh, N., Wainwright-Evans, S., & Justice, A. (2020). Fluence Cannabis Cultivation Guide. Fluence by Osram. Retrieved September 11, 2022, from https://1gt3sd9flvb3kwgha3wmyhbu-wpengine.netdna-ssl.com/wp-content/uploads/2020/02/FLU-CultivationGuide_Cannabis_WEB_PROOF_01-2020.pdf

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Robert Hammell

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