Temperature effects on cannabis growth

Growing the cannabis plant is relatively easy and straightforward.  The plant is hardy to a wide range of temperatures.  Growing at an industrial scale, however, is much different, as temperature and humidity can affect the growth rate of the plant as well as flower quality.  For such a multibillion-dollar industry as cannabis, growth temperature is extremely important to help maintain high quality and consistency among the entire cannabis crop.

              The cannabis business is expected to grow exponentially as more states legalize both medicinal and recreational uses for the plant.  With revenue projected at around $20 billion dollars by 2022, growers have an incentive to maximize the quality and quantity of their product.¹  While several factors, such as hours of sunlight and soil content, contribute to plant health, temperature plays an important role in growth rate and quality of flower production.  Throughout the four stages of growth, seedling, vegetation, flowering, and late flowering, the cannabis plant prefers certain temperatures to produce at the best levels.¹ As well, depending on what the grower is trying to achieve, for instance THC content, temperature is also important.  The strain of cannabis also determines the optimum temperature for production.  There are strains that prefer high temperatures, such as Kaya Gold, because they are originally from warmer climates.¹ It appears that African and Hawaiian strains also tend to be more heat resistant, while autoflowering strains originating in Siberia are often heat sensitive.¹  While strain type does matter, in general, certain temperature ranges and drops during the night are appropriate for most plant types.

              The best range to grow cannabis is between 22 – 24^o C during the day and 2 – 5^oC during the night.  The cannabis plant, however, does not react well to changes is temperature of more than 8^oC at a time.  More that this can shock the plant and severely affect growth rate.² In the seedling stage, cannabis prefers temperatures in the 24 – 27^oC.³  Clone cuttings also prefer the same temperature range.⁴ In the vegetation stage, when the plant produces its signature leaves, the best temperature range is 21 – 26^oC.  Flowering plants seem to prefer a smaller range of temperatures, around 20 – 24^oC.⁴ Finally, the late flowering period, which is when the plant reaches maturity over six to 12 weeks, temperature between 21 – 27^oC seem to produce the best quality flower.³ Colder temperatures tend to affect cannabis much more negatively than warmer temperatures. In warmer temperatures, growth may slow, and flowers tend to be less dense, but the plant can still thrive.  On the other hand, when temperatures are too low, the root system is affected, and nutrient absorption is lowered. This can cause a deficiency in vital minerals such as magnesium.⁵ Mold and other contaminants also thrive at lower temperatures and may form on the root systems. As well, under 15^oC the leaves will start to curl and the plant will eventually die.⁶  

              There are many factors that influence the cannabis plant during its cultivation.  Temperature is one of the most important of these that can contribute to growth rate and flower quality.  In general, cannabis prefers warmer temperatures because of the warmer climates from which they arise.  While temperature is strain dependent, as a whole, cannabis does not like large temperature swings and cannot survive below 15^oC.  Too high temperatures can stunt growth and create sparse flowers.  Industrial scale growers regulate temperature very closely, as it can greatly affect the overall quality and quantity of their product.

References:

1. Cannabis temperature tutorial. Grow weed easy website. https://www.growweedeasy.com/temperature#why-temperature-matters-to-YOU-as-a-grower. Accessed on June 15, 2020.
2. Cannabis temperature for indoor grow rooms. Green CulturED website. https://www.greencultured.co/cannabis-temperature-indoor-grow-rooms. Accessed on June 15, 2020.
3. Temperatures and medical cannabis growing from seedling to harvest. SensoScientific website. https://www.sensoscientific.com/blog-temperatures-and-medical-cannabis. Accessed on June 15, 2020.
4. What’s the best grow room temperature and humidity level? High Times website. https://hightimes.com/grow/best-grow-room-temperature. Accessed on June 15, 2020.
5. The effect of cold on cannabis plants. Alchimia website. https://www.alchimiaweb.com/blogen/the-cold-during-a-cannabis-plant-crop. Accessed on June 15, 2020.
6. The ideal temperature for growing cannabis. Cannaconnection website. https://www.cannaconnection.com/blog/2245-ideal-temperature-growing. Accessed on June 15, 2020.