What are Trichomes?

Trichomes are one of the coolest features on the cannabis plant. Not only do they look and smell interesting – they have a wide range of functions that contribute to the wellbeing of both the plant and its consumers.

Consumers, cultivators and botanists alike will all testify that the cannabis plant is a visually appealing specimen. The flowers host multiple shades of green and can be accented by vivid colours such as purple and pink, while there are also numerous features that the eye can be drawn to.

Perhaps the most interesting of all these features though is the trichomes – and not just because of the way they look.

What are trichomes?

Trichomes are clear appendages that protrude from plants such as algae, lichens and of course, cannabis. They appear all over the surface of cannabis plants and are mainly produced on the flowers, stems and the leaves. These trichomes can be made of hairs, glandular hairs, scales and papillae.

If you've looked at a cannabis plant before, or even just the buds, then you may have noticed that they can have a frosty-looking exterior. This is actually due to the trichomes, as they have a shiny, crystal-like appearance. It is believed that a high concentration of trichomes on the buds is an indication of the strain having high potency.

But what is the rationale behind this train of thought?

Well, trichomes contain secretory glands that produce a clear, glossy resin. This resin coats the surfaces of the plants, which is the reason why cannabis flowers and leaves have a sticky texture.

The resin is responsible for the flavours and aroma of the plant but that's not where the fun stops. It also contains all the cannabinoids, such as THC and CBD, terpenes, flavonoids and various other phytochemicals which contribute to a strain's potency, effects and unique therapeutic profile.

Types of trichomes

Trichomes fall into two main categories, with their classification dependent on their ability to secrete this resin. Glandular trichomes produce cannabinoids, terpenes and flavonoids and are able to secrete them in a resin via their secretory glands. Non-glandular trichomes, also known as cystoliths, do not secret resin.

Of the glandular trichomes, there are also three sub-categories that exist: bulbous, capitate-sessile and capitate-stalked.

Bulbous trichomes are tiny bulbs that cannot be seen without the aid of a microscope. They are evenly distributed along the surface of the cannabis plant and are not specific to any particular area. They are responsible for the frosty appearance and sticky texture of the plant, however, their ability to produce cannabinoids is still in question.

Capitate-sessile trichomes are larger and more abundant than bulbous trichomes but a microscope is still required in order to observe them. These trichomes have large bulbs and can be found on the underside of the sugar and fan leaves. They have secretory cells at their base, which are responsible for synthesising phytocannabinoids and terpenes.

Capitate-stalked trichomes are more abundant and much larger than the other varieties and can easily be seen by the naked eye. This type of trichome is mainly found on the cannabis flowers and is rarely seen on the leaves. Their structure is comprised of a large glandular bulb that sits atop a multicellular stalk. This bulb is the epicentre of phytochemical production, making these trichomes the powerhouses of strain potency.

The iconic capitate-stalked trichomes

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Trichome function

Trichomes can be found covering the surfaces of many plants throughout nature. They can have a wide range of functions and are not just specific to the cannabis plant. For example, trichomes are present on some varieties of carnivorous plants, where their stickiness allows them to capture prey. In contrast, cannabis trichomes function as a defence mechanism. 

During cultivation, their primary function is deterring pests and predators, while also protecting the plant from any other environmental stressors. Female cannabis plants that have begun to flower can become vulnerable to insects, animals and environmental conditions such as harmful UV rays.

The non-glandular trichomes known as cystoliths act as a pest deterrent by trapping and impaling small insects, while glandular trichomes produce terpenes which have a bitter taste and pungent aroma that pests find unpalatable. Trichomes also protect the plant from damaging winds, inhibit fungal growth and maintain an optimal level of surface-level humidity so that the leaves don't dry out.

As mentioned earlier, the most interesting function of trichomes (at least from a pharmacological perspective) is their ability to produce and secrete a range of phytochemicals. Clinically relevant molecules such as cannabinoids, terpenes and flavonoids are all produced within trichome cells through biosynthesis.

In this process, enzymes catalyse a series of chemical reactions that produce complex molecules from smaller molecules. In regards to cannabinoid biosynthesis, the primary enzymes involved are cannabidiolic acid (CBDA) synthase, cannabichromenic acid (CBCA) synthase, and tetrahydrocannabinolic acid (THCA) synthase.

Following the three basic steps of cannabinoid biosynthesis, which are binding, prenylation and cyclization, these enzymes convert precursors such as cannabigerovarin acid (CBGVA) and cannabigerolic acid (CBGA) into the acidic cannabinoids THCA and CBDA. These acidic cannabinoids can then further be altered by decarboxylation, to become THC and CBD, the forms that produce physiological effects.

Trichome production

Cannabinoid biosynthesis only commences within the trichome once the plant has entered its bloom phase. When the plant starts to flower, trichomes will start to form along the surfaces of the plant, where they will begin to metabolise the precursors necessary for cannabinoid synthesis.

There are many factors that can influence the concentration and growth rate of cannabis trichomes, with plant genetics and the environment playing a major role. For example, UV light can greatly affect phytochemical production, as plants that receive a broader spectrum of light typically produce higher concentrations of cannabinoids.

Trichomes will begin to display maturation when they change from a clear and translucent state to a cloudy white colour. This transition in colour indicates when a trichome has reached its 'peak ripeness' (i.e. the highest concentration of phytochemicals produced). Cannabis cultivators use this as an indication for when to harvest, as degradation begins shortly after this point and can be observed as the trichomes change from white to amber. 

Trichomes are also extremely fragile and can be destroyed or degraded through things such as excessive physical contact, overexposure to heat and light, oxidation and long durations of time. Cannabis cultivators are proficient in mitigating these risks to preserve the trichomes and their phytochemicals for as long as they can.

Cannabis concentrates

Another option for extending the life of trichomes and all the goodies they produce is by converting them into cannabis concentrates. Nearly all concentrates on the market stem from trichomes or from extracting the phytochemical soup contained within. These products have become insanely popular amongst cannabis consumers and are largely utilised due to their potency and ease of consumption.

To make cannabis concentrates, desirable compounds such as cannabinoids, terpenes and flavonoids are isolated and extracted from the plant's trichome glands. The two main modes of separating trichomes from cannabis plants are physical separation and chemical extraction.

Physical separation involves processes that break and remove the trichomes from the plant material. One method is by shaking the trichomes of the plant, as witnessed in the creation of dry sift or kief. These two terms are interchangeable and refer to the trichome glands that have fallen off the plant matter. This kief can then be pressed and turned into a concentrate such as hashish.

A collection of trichomes removed from the cannabis plant, also known as 'kief'

Another method of physical separation is by pressing cannabis flower in a heated press. The heat melts the trichomes into a resin that contains numerous phytochemicals, with the resulting product being known as rosin.

Chemical extraction utilises chemical solvents, such as ethanol, butane and supercritical CO2, to dissolve the trichomes from the plant. Solvent-based extraction is widely accepted as the most efficient method of trichome removal and is the preferred method for most manufacturers in the cannabis industry.

Trichomes are truly deserving of appreciation, so be sure to check them out the next time you're looking at a cannabis plant. Not only do they help protect the plant from any external danger, they produce all the chemicals that cannabis is associated with. Future research into trichomes will help to uncover even more medical and recreational applications for the cannabis plant.

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Josh Griffin
Josh Griffin

Josh is a Perth-based writer with a background in psychology and pharmacology. Through his studies he has gained an interest in abnormal psychology, mental health and psychopharmacology and has reported on these topics. Currently, his main focus is on cannabinoids and their medical potential.

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