Trichomes are the hair-like structures found on plants. Stinging nettles have trichomes that inject an irritant when they are brushed, mint plants have trichomes containing the essential oils that give them their distinctive smell, and sundew plants have sticky trichomes that trap insects.
Cannabis also has trichomes containing concentrations of more than a hundred different cannabinoids including the best-known: tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN). These trichomes also contain terpenes, which account for many of differences in aroma and flavor between different varieties. Common terpenes include earthy myrcene, lemony limonene, flowery linalool, piney pinene, hoppy humulene, spicy-woody beta-caryophyllene, and many others. In terms of consumption, the rest of the plant material (leaves, flowers, etc.) can generally be thought of as carriers for the active ingredients in the trichome material.
Hash and other concentrates are variations on the same theme, separating the contents of the trichomes from the rest of the plant material. Consuming trichomes without the additional plant material tends to have a similar effect to consuming the same amount of trichome material still in buds, but can be consumed faster and takes up less space for transportation and storage. Consuming leftover plant material that has had the trichome material removed will have little to no “high” effect depending on the efficiency of the extraction.
So, technically, it isn’t the female flowers that are the most desirable portion of the plant, but the trichomes found on and around the flowers. While trichomes can appear on many parts of the cannabis plant, they tend to be found in the highest numbers on the flower bracts and the immediately surrounding foliage.
Since the trichomes are where the active ingredients are, it makes sense to consult them when judging the best time to harvest. Indicators such as the wilting of the stigmas (the white hairs at the end of the pistil), a stronger aroma, and the swelling of the buds usually happen in a similar time frame to trichomes ripening, but direct observation of the trichomes themselves can give a more exact harvest window.
Trichome sites on a particular leaf are established early in a leaf’s growth. These trichomes grow in size, first creating their desirable components and then maturing them. Trichome maturity has basically three stages:
Immature trichomes tend to be clear or lightly tinted. These have little effect as they have not yet had time to fully develop their cannabinoids. Cannabis harvested with mostly clear trichomes will not only have a reduced effect when consumed, but will yield less than the plant would have if allowed to mature before harvesting. Clear trichomes tend to be the least desirable of the three stages.
Cloudy trichomes have had time to develop into their mature stage, and are more potent than their clear counterparts. These will generally turn to a more amber color as they age.
Recently turned, amber-colored trichomes are generally considered to be past their “prime” but still retain a fair amount of potency.
By looking at the trichomes through magnification from a scope or a photo, their maturity and suitability can be determined. Since the trichomes do not all mature at the same time, judging can be done by gauging the rough ratios of clear to cloudy to amber.
It is generally accepted that you’re too early if most of the trichomes are still clear. It isn’t until at least some of the oldest trichomes have started to turn amber and most of the trichomes are cloudy that harvesting should be considered, at the earliest. The exact ratio of cloudy to amber trichomes has to do with the peculiarities of the particular variety and the preference of the gardener, although somewhere in the neighborhood of 25-percent clear, 50-percent cloudy, and 25-percent amber is a common rule of thumb. To determine personal preference, samples are sometimes taken at various stages and consumed to associate a particular ratio with its effect on the resulting product.
After harvesting, care should be taken to protect the trichomes from damage. The buds should be dried or frozen before mold can set in. If the trichomes are going to be left attached to the flowers, the buds should be cured after drying to improve the flavor of the plant material. If the flowers were fresh frozen for use in concentrates, they do not require a curing period because the plant material is removed as part of the process. Trichomes, in whatever form, should be stored in a cool, dry location in an opaque, airtight container.
Unless exposed to heat (or enough time), much of the THC found in trichomes is in an acidic form known as THCa, which is basically THC with enough extra atoms to make an attached carbon dioxide (CO2) molecule. Decarboxylation is the process of driving off this extra carbon dioxide turning the THCa into the active form, THC.
If the trichomes are consumed using a method that involves heat (smoking, vaping, dabbing), then decarboxylation occurs as the THCa is exposed to the high temperatures of the ingestion method. If they are going to be consumed in a form that is not heated to decarboxylation temperatures, such as with many edibles, then they should undergo the heating in an additional process. The temperature needed is inversely proportional to the time needed. When exposed to high heat, the reaction can take place in a fraction of a second, but will take longer with lower temperatures.
To decarb the trichomes, expose them to temperatures through processes such as 90 minutes in boiling water (in a sealed boiler-safe bag) or an hour or so on a sheet pan (stirring occasionally) in a 230-degrees Fahrenheit oven.
Trichomes are the jewels of the cannabis plant, and when allowed to mature properly, stored properly, and decarbed as needed, are what yields the wondrous effects most commonly attributed to cannabis consumption.