Why Does Cannabis Produce THC?

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Categories : Medical cannabis

Why Does Cannabis Produce THC?

THC, the psychoactive cannabinoid, is produced by the cannabis plant to protect the plant from disease, predators, heat and UV rays.

THC or Δ9-tetrahydrocannabinol is the cannabinoid, that gives cannabis its zing, if not creates, at least in some users, the “high”, that creates euphoria, as well as provides significant relief for medical users.

It is one of the many cannabinoids found in the cannabis plant. But why exactly does the cannabis plant produce this wondrous substance in the first place?


All cannabinoids (including THC and CBD) are produced in glands along the surface of the leaves called trichomes. Trichomes are not unique to cannabis. In fact many plants have them and their purpose is generally the same in all of them. They help defend the plant from natural predators, weather, water and to attract pollinators.

Caffeine and nicotine for example, are also produced trichomes – and like cannabinoids also act as natural pesticides and to deter predators.

The flowering buds of the female cannabis plant have the highest concentrations of THC, followed by the leaves, stalks and stems of the plant.


Cannabis has three different kinds of trichomes. The first are bulbous trichomes, which are the smallest of the three. They appear on the surface of the plant. They are usually between 10-15 micrometres in size (or just a couple of cells).

The second kind of trichomes on cannabis are a bit larger and contain both a head and a stalk. They are more numerous than bulbous trichomes.

The most numerous and largest of the trichomes on the cannabis plant are called capitate-stalked trichomes. They can be anywhere from 50-100µm wide, can be seen by the naked eye and are comprised of a stalk and stem, topped by a large gland head. This gland head, which is protected by a waxy cuticle layer, is where most cannabinoids are produced.

Cannabis THC


One of the theories about why cannabis produces THC is to protect the plant from “infection” or disease. THC has strong antimicrobial properties in humans. It may be, that it serves the same purpose for the plant that produces them: they are the cannabis plant’s “immune system”.

But not so fast. Higher THC plants are not more resistant to pathogens and pests than those with less THC.


Another answer might be that THC (as a specific cannabinoid) might protect the cannabis plant from absorbing too much ultraviolet light. A recent study from the University of Maryland exposed a variety of cannabis plants from different parts of the world to UVB rays. The study found, that plants exposed to this kind of light produced more THC than those that were not exposed.

Cannabis plants thrive in open areas with lots of direct light – either from the sun or grow lamps.


Cannabinoid synthesis begins as plants move into their bloom phase. As they produce flowers, trichome cells within the gland head begin to metabolize what will become THC. Trichomes will display maturity when they change colour – going from a clear and translucent state to a cloudy white and then amber colour. This change of colour represents its peak ripeness and is also an indicator for the peak time to harvest the plant.

That said, not all strains of cannabis are the same and different strains have trichomes, that mature differently. Either when alive on the vine or after harvest, trichomes are also fragile and can be destroyed or degraded by rough handling, light, heat, air and time. In addition to the trichomes themselves risk damage, but the essential oils they also contain can also be degraded.

To limit this potential, it is very important to protect the flowers from too much physical contact. Proper trimming, drying and curing techniques can also help keep trichomes viable for longer.


Different strains of marijuana also contain different levels of THC. Plant genetics determine the amount of THC a plant can produce, although growing methods can also boost THC content. To get really high levels of potency and THC, it is essential to start with high-potential strains.

Some of the higher concentrate (and faster growing) high potency strains include:

Super Silver Haze – An all-time classic, particularly in Dutch coffee shops.

Super Silver Haze

Choco Candy – A hybrid created by the crossing of Chocolate Haze with OG Chocolate Thai, this strain has a deeply satisfying, aromatic taste and also has a high THC concentration of 21%.

Choco Candy

Amnesia Haze XL – Amnesia Haze XL is not only a fast bloomer, it also has a deliciously citrus flavour.

Amnesia Haze XL