Cannabis Science

28 September 2021

The Role of Trichomes in Cannabis

Have you ever held a juicy nug in your hand and noticed how shiny and sticky it was? Take a closer look, and you will see hundreds of tiny, translucent, and amber crystals dotting the flower’s surface. These crystals are known as trichomes, and they are essential whether you are a cannabis cultivator, connoisseur, extraction artist, or novice consumer.

Trichomes are so vital because they produce and house the chemical compounds that give cannabis flowers their flavours and psychoactive effects. Cannabinoids, terpenes, and flavonoids are all found in the tiny little crystals. Trichomes are so prized that farmers in California’s Emerald Triangle have said they cultivate trichomes as much as flowers.

But what exactly are trichomes, and how do they develop? Read on to learn more about these incredible, tiny chemical factories that give cannabis flowers their potential beneficial effects.

Plant Trichomes Come in All Shapes and Sizes

Trichomes (from the Greek word “Tríchōma” or “growth of hair”) are outgrowths from the epidermis of plants. They are external structures that help move products of plant metabolism to different parts of the plant via secretion. Secretion is the movement of plant material, such as chemical substances, from secretory cells or glands.

The epidermis is the outer layer of cells of a plant that includes the stem, leaf, roots, seed, and flower organs. The epidermis protects the plant from various threats such as water loss and damage from invasive pests and pathogens.

Plants, unlike animals, are unable to get rid of waste and other metabolic products through sweat glands or digestive and urinary systems. Instead, such products are stored within individual cells or transferred to other parts of the plant.

The epidermis plays a crucial role in the transfer and storage of certain intermediate or end products of plant metabolism. For example, oxygen is released through the epidermis after photosynthesis.

Trichomes on the epidermis provide a similar service. They are highly specialised cells and come in different forms, but all are found on the surface of the epidermis. There are many different types of trichomes, and they manifest as tiny hairs, scales, or in the case of cannabis, glands.

Terpenes and other essential oils produced and stored in trichomes provide flowers with fragrance to attract pollinators. In addition, defensive compounds such as alkaloids found in the trichomes of poppies are highly poisonous with a bitter taste that deters herbivores.

One well-known example of defensive trichomes are the hairs found on stinging nettles. Nectaries are trichomes that attract bird and insect pollinators by secreting a sugar solution (nectar). Salt glands found in coastal marine and saltmarsh plants are modified trichomes that help the plant get rid of excess salt absorbed from the environment.

Cannabis trichomes are just as unique. So let’s take a closer look at how they develop and why they are so prized by cultivators.

Cannabis Trichomes – Tiny, Delicate, and Specialised Chemical Factories

Google “cannabis trichomes”, and you will be greeted with images of translucent, alien mushrooms on the surface of the cannabis flower. These are known as glandular trichomes, and they are characterised by a globe-shaped appearance. Of all the compounds plants produce, terpenes are among the most common in glandular trichomes.

Cannabis trichomes consist of a stalk rising from the epidermis that is one or more cells long and holds an expanded globular gland. This gland contains an outer protective cuticle layer in addition to an internal, subcuticular layer in between the cuticle and its contents. Terpenes, as well as chemical precursors to THC, such as cannabigerolic acid (or CBGA), form in the gland.

This trichome configuration provides extra protection to the valuable chemicals (also referred to as secondary metabolites) housed inside trichomes and is a feature of both cannabis and hops. Larger glands contain more THC and CBD precursors, as well as terpenes, and are the reason why well-developed trichomes are highly sought-after among cannabis cultivators.

Cannabis flowers develop three types of trichomes, categorised by size and stage of development:

1 . Bulbous trichomes are generally the smallest variety and contain limited amounts of secondary metabolites. There is no discernible stalk between the gland and epidermal surface
2 . Capitate-sessile trichomes sit above the epidermis atop tiny stalks and tend to be a little bigger than their bulbous counterparts.
3 . Capitate-stalked trichomes are taller than sessile and have larger glands containing the highest concentration of secondary metabolites. The stalk is observed to be “multicellular”, and these are the trichome heads that are most visible to the naked eye.

Cultivators who are hunting for desirable strains ought to pheno-hunt ones that produce capitate-stalked trichomes, as these will contain the largest amount of cannabinoids and terpenes. However, there is another reason for choosing capitate-stalked trichomes, which has to do with plant defence.

While humans experience beneficial effects from consuming the chemicals produced by cannabis, the plants evolved these compounds as a defence. There is evidence that trichomes help prevent water loss and lower plant surface temperatures during periods of heating.

Trichomes and their contents are spread over the surface of the epidermis of marijuana plants. This protects the plant’s surface from insect damage via insecticidal and behaviour-modifying effects. They also act as a barrier between the epidermis and pathogens such as fungi and smaller predatory insects that may not be able to penetrate through the dense layers.

It stands to reason that bulbous or even capitate-sessile trichomes, being smaller and less full of compounds than their capitate-stalked counterparts, would be less effective at mitigating pests and pathogens.

How trichomes Inform Cultivators of Ripeness

Like the plants that produce them, trichomes have a developmental life cycle. When cannabis plants reach the flowering stage, they begin to produce cannabinoids and terpenes. Trichomes develop on the epidermis, and flowers will begin to be fragrant and sticky.

Cultivators keeping an eye on their strains should take note of earlier-than-usual resinous extension, usually along the sugar leaves. This is typically a sign of enhanced trichome production. A jeweller’s loupe with light is a valuable tool for a cultivator to keep an eye on the development of their plant’s trichomes.

As cannabis flowers mature, trichomes will undergo a steady and noticeable transformation. The trichome glands will first appear transparent (or translucent), a sign that they are not yet ready for harvest. In the next stage, the glands will become cloudy, indicating a peak concentration of cannabinoids and terpenes.

Cultivators growing sativa-dominant strains should consider harvesting their flowers when trichomes are in the second stage. Flowers harvested with cloudy trichomes provide an energetic head high as a result of the accumulation of cannabinoids. However, this is a limited window, as cloudy trichomes will develop an amber hue before long.

In the third stage, cloudy glands will begin to turn amber, and there will be a mix of cloudy and amber trichomes. In this stage, cannabinoids and terpenes start to deteriorate due to overexposure to the elements and their lifespan. The decreased concentration of THC levels will lead to a relaxing body high, so indica-dominant strains should be harvested during this stage.

The final stage of trichome development is characterised by most or all trichomes appearing amber. This indicates that there has been significant deterioration of cannabinoids and terpenes. A lower concentration of cannabinoids will lead to a very mellow smoking experience.

Cultivators should take care not to leave flowers on for too long before harvesting. The deterioration of chemical compounds can lead to undesired surprises. For example, orange terpenes may start to smell like BBQ chicken when the trichomes are past their point of ripeness (true story!)

Preserving Trichomes After Harvest

You might think the battle is won after harvest time, but that is not the case. A bountiful harvest can be ruined as trichomes are incredibly delicate and can continue to deteriorate in the wrong conditions.

Trichomes can be destroyed by agitation (being too rough with harvested flowers), exposure to UV rays, heat, oxygen, or may simply degrade over time. Therefore, harvested cannabis buds should be treated as gently as possible and not exposed to any direct light during the drying period.

Cultivators should aim to keep their drying and curing conditions as stable as they can. A proactive approach is better than a reactive one, as often disaster has already struck before any semblance of control can be regained. Therefore, maintain a methodical and attentive approach, and use tools and equipment such as dehumidifiers and thermo-hygrometers to stay on top of dry room conditions.

Generally speaking, a temperature of between 15-21 degrees C and humidity of 45-55% will maintain trichomes during the drying period. A two-to-three-week curing period in airtight, UV glass jars will help preserve trichomes on nugs as much as possible.

Growers looking for the best place to start their trichome tour should start using the highest quality seed available. Check out Marijuana Grow Shop and browse our high-quality collection of seeds sourced from some of the world’s most skilled and passionate cultivators. MGS helps growers of any level search for their favourite cannabis strain by genetics, medical symptoms, varieties, and even desired effects.

Post author
Martin
Martin is a production horticulturist with experience in commercial cannabis cultivation and sustainable farming from his time with Emerald Cup Award-winning farmers Esensia Gardens in northern California's Emerald Triangle.
See more from Martin

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