Growing for Terpenes

When asked by my dear friend Ellen, the editor in chief of this publication, to resume writing for High Times I jumped at the request. As a journalist/educator and lifetime student I’ve always enjoyed diving into topics that I’ve covered for this magazine over the years and revisiting certain subjects as new science became available. Here I look into growing cannabis specifically for terpene production.

Terpenoids or terpenes are one of the most important chemical compounds produced by the cannabis plant. They are the compounds responsible for the plant’s smell and give each cultivar their unique perfume. Terpenes, like cannabinoids, are produced in the plant’s trichome. The trichomes are the little appendages that grow out of the plant, they are found on the buds as well as sometimes on the leaves of the plant. In the cannabis plant they are typically comprised of a stalk and head. Inside these heads are most of the essential oils found in the cannabis plant, including the cannabinoids, terpenes, flavonoids, and other compounds.

Currently there is a shift in the dialogue regarding THC percentage and its sole importance to selling cannabis in the many legal markets around the world. This should be understood as fantastic news to consumers, as they will finally be the beneficiaries of more knowledge surrounding the plant and the way in which its active compounds work with each other to steer effects. This has come to be known as the entourage effect. THC is like the gas of the car and the terpenes and other compounds act like the GPS, giving the high its direction.

The first researchers to discuss the entourage effect were Dr. Raphael Mechoulam and Dr. Shimon Ben-Shabat. They proposed that the combined effect of all the compounds found in the trichome head worked in a “botanical synergy,” to maximize the pharmacological effect of cannabis. This concept was further expanded by Dr. Ethan Russo in a paper he wrote in 2011. In the British Journal of Pharmacology, Dr. Russo wrote “that phytocannabinoid-terpenoid interactions found in cannabis offer complementary pharmacological activities that may strengthen and broaden clinical applications and improve the therapeutic index of cannabis extracts.”

This discussion has mirrored improvements in the cultivation of cannabis and have shown that phytocannabinoids and terpene percentages rise to unbelievable levels. It’s not uncommon for some strains to test as high as 35-38% total cannabinoids, with some flower testing as high as 5.5-6% total terpene content. As more cannabis research emerges, cultivation techniques are becoming more and more refined. Using a science-backed approach, cultivators can test their flower and really dial in environment, nutrient usage, and genetics. When it comes to growing for terpene content, the main factors a grower can control are: nutrients, ultraviolet (UV) light, temperature control, harvesting schedule, the drying/curing process, and genetics.

Nutrients

Nutrients, specifically certain plant hormones like methyl jasmonate, can stimulate the systemic acquired resistance (SAR) in a plant. This forces it to increase the natural oils, in this case terpenes, flavonoids and cannabinoids, as a means of protection. Another way to access this response is something called salicylic acid. In an article found in the journal, Food Science and Nutrition, a team of botanists from Urmia University of Medical Sciences in Iran, discovered that using salicylic acid as a foliar feed can increase cannabinoid, flavonoid, and terpene production. When sprayed on the cannabis plant the acid regulates the jasmonate signaling pathway naturally found in cannabis. This makes the flavonoid and terpene synthesis more efficient, increasing their values by several percentage points. The most well-known nutrient used for terpene enhancement is the Terpinator. The product contains no methyl jasmonate or salicylic acid, instead its main ingredient is potassium (K) which increases enzyme activity making the essential oil production more efficient. Another product on the market is FlaVUH from Ventana Plant Science; it uses a proprietary polyaspartic amino acid which increases the nutrient uptake to the plant, increasing yield and natural oil production. It also contains no jasmonate or salicylic acid.

UV Light

UV light has been found to also have a big impact on terpene production as well as an increase in cannabinoids. This comes from the fact that the plant naturally protects itself from UV light by increasing essential oil production. One of the more interesting advances in cultivation has been the improvement in the quality of LED lights. In recent years LED fixture companies have added UV diodes to their lighting fixtures, which causes cannabinoid and terpene values to increase. The long time question surrounding the benefits of outdoor vs. indoor cultivating has also found new evidence to support the benefits of UV light. In the journal Molecules a group of scientists from Columbia University, in partnership with several cultivators in California, tested the difference between outdoor and indoor cultivation. Using the same clones, medium, and nutrient regiments, they grew plants in outdoor farms and under artificial lights. Their discovery showed that not only were the terpene and cannabinoids higher in outdoor grows, but that there were also unique terpenes and minor cannabinoids detected in the plants grown outdoors. Additionally, the percentages of sesquiterpenes like b-caryophyllene and a-humulene were higher in the outdoor plants. One could speculate that those terpenes were more present in the outdoor plants because they needed extra protection from the UV light.

Temperature Control

Temperature control is another important factor in the production of terpenes. Typically by lowering the temperatures at the end of your flower cycle you will also see an increase in terpene production. Usually a drop between 5-10 degrees Fahrenheit will do the trick. An added benefit to dropping the temperatures is that flavonoid production will also increase and the plants that naturally get purple will also increase the amount of color present in the buds.

Harvesting Schedule

A harvesting schedule is a fairly easy factor to control since the advent of cannabinoid and terpene testing labs. In the past we had to rely on loupes or magnifying glasses to study the color of the trichomes. Now you can test your flower at any point in the harvest cycle and pick the perfect moment of ripeness, depending on your needs. Usually for terpene production you want to harvest a bit on the earlier side, whereas with THC you’ll want to harvest a bit later in the cycle.

Drying & Curing

Drying and curing is just as important a process as growing is. Most people forget that your nine weeks of work can easily be ruined by an improper cure or storage. Especially in cities like Denver where the altitude can easily dry out your flower. My preference for drying is a lower temperature environment between 45-50 degrees Fahrenheit and around 55-60% relative humidity. I also like to keep the fan leaves on the plant as well as keeping the plant as intact as possible. This allows the cannabis to dry at the slowest possible rate preserving the essential oils. As for storage, glass is always better than plastic, unless you can nitrogen flush and vacuum seal the bags. The key to storing flower is to have a full jar. The head space in the jar, which is the native space between the lid and the flower is what causes the terpenes to slowly evaporate, therefore pick a jar size that can be filled to the top. Some people also swear by the use of the humidity-regulating packs. I personally have found that they cause a reaction to some of the more volatile terpenes with the result being a more homogenous smell across different cultivars. I would say invest in some research and test your flower before and after using any humidity packs to see if they work for you.

Genetics

Finally, genetics can also play an important role in terpene-rich flower. The key here is to experiment with your environment and keep testing. Test which cultivars work best for you, for your environment and for the nutrient program you are using. Science is your ally here, use cannabis testing labs to your advantage. Remember that science is based on proof and not belief, so using it will help you discover more about your flower and the chemical compounds found within. This will allow you to grow the dankest, loudest, and most potent flower you can. May the terpenes be with you.

This article was originally published in the May 2023 issue of High Times Magazine.