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Trichomes: Fruit of the cannabis plant
The pharmacologically active components of the cannabis plant, the cannabinoids and terpenes, collect in microscopic glandular structures known as trichomes. These are tiny outgrowths from the surface of a plant similar to a hair. The most abundant type of trichome on the cannabis plant are capitate stalked glandular trichomes, which resemble a ball on the end of a stick. The “ball” is the glandular head of the trichome, which collects cannabinoids, terpenes and other active compounds within a waxy cuticle. This structure could be compared to a fruit or vegetable, with the waxy cuticle being the skin and the interior the flesh. Similar to many crops, when the cannabis plant and its trichomes have matured to be “ripe”, the glandular heads can be easily separated from the plant by gentle agitation. The physical process of removing the trichomes from the plant matter has been practiced for thousands of years to produce keif and hash.
Over the past 50 years, the average potency of herbal cannabis has increased significantly due to specialized breeding, cultivation, and processing techniques. This rise in potency has come from increasing the size and number of trichomes on the female flowers. Similar to breeding food crops to produce more fruit per plant, by increasing the number of trichomes there is a greater ratio of active molecules to inert plant matter. Breeders have selected plants with the most and largest trichomes over many generations to produce plants with higher potency genetics. The technique of removing male plants to stop fertilization increases the concentration of trichomes on the unfertilized female flowers, and this is a standard and vital technique for cannabis growing today. After harvest, the flowering tops are removed from the stalk and trimmed to remove leaves with lower concentrations of trichomes. This post harvest processing increases the ratio of trichomes to plant matter in the final saleable product, cannabis buds, to maximize its potency. Using these methods, while providing optimal growth conditions, the concentration of cannabinoids in dry herbal cannabis can approach 35%. Many plants produce secondary metabolites of medical interest, but most often at quite low concentrations, 1-5% of dry weight for example. By secreting the cannabinoids and terpenes into a trichome, the cannabis plant can collect these metabolites in much higher concentrations. If these compounds were contained within regular plant cells, such high concentrations could interfere with its metabolism and become toxic. By using a trichome to collect its medical components, the cannabis plant can collect the highest known concentrations of active metabolites of any plant known to science.
When compounds collect within plant cells, their extraction requires a solvent to free them from the plant matrix. Extraction methods such as Super-Critical CO2 were developed to break open plant cells and free hard to extract metabolites. Such methods are not completely necessary with cannabis, since the trichomes are so easily accessible. Trichomes heads can be broken from the stalk and separated from the plant matter using simple physical methods, like sifting dry material over a screen or agitating cannabis in cold water. By collecting just the trichome heads and separating the rest of the material, kief or hash is created. The potency of trichomes can reach up to 80% cannabinoids! This is a basic component of the cannabis pant, and while kief or hash is often referred to as a cannabis “concentrate” this may not be the best terminology. If one removes all the seeds of the pomegranate from the pith would you call that pomegranate “concentrate”? Would you call shelled hemp seeds or walnuts an “extract”? While the production of kief or hash most definitely concentrates cannabinoids more than in herbal cannabis, it is not much different than “concentrating” the edible components of food crops by removing the inedible parts like leaves, stalks, husks or shells.
The glandular trichome of the cannabis plant is a biosynthetic powerhouse. Its physiology allows cannabis to produce active metabolites in concentrations impossible for most other plants, and also makes the collection of these compounds easy and inexpensive. While some people have started to make cannabinoids in yeast to bypass plant production, this seems entirely unnecessary considering the efficiency of cannabinoid production in trichomes. Rather than utilize yeast to grow cannabinoids, perhaps we should be utilizing trichomes to produce other compounds of interest.