Short answer
Terpenes are the volatile compounds that give cannabis most of its smell and taste: myrcene, limonene, β-caryophyllene, pinene, terpinolene and many more. The plant makes them in its glandular trichomes, alongside cannabinoids. Total terpenes average about 2% of flower weight. Established chemistry.
Why
Terpenes are made in the resin glands. Terpene synthase enzymes in the trichomes build monoterpenes (10 carbons, lighter and more volatile) and sesquiterpenes (15 carbons, heavier) from shared precursors [1]. Which synthase genes a plant carries largely sets its profile [1][5].
Commercial flower clusters into a few profiles. In 89,923 US lab results, THC-dominant flower fell into three terpene groups: caryophyllene–limonene, myrcene–pinene and terpinolene–myrcene, with the first two holding 87.4% of samples [2].
Not every smell is a terpene. The fuel-like "gas" note comes mostly from trace prenylated sulfur compounds, detected at tiny levels [3].
Terpenes are fragile. Monoterpenes evaporate and oxidise with heat, air and time. Gamma irradiation cut some volatile monoterpenes by 10–20%, up to 38% for one compound [4]; slow drying and cool, dark, airtight storage keep more.
Labels track terpenes loosely. "Indica" and "sativa" tags associate with a few terpenes, not with genome-wide ancestry [5].
The numbers
| Terpene |
Class |
Common aroma |
| Myrcene |
Monoterpene |
Earthy, musky |
| Limonene |
Monoterpene |
Citrus |
| α- and β-pinene |
Monoterpene |
Pine |
| Terpinolene |
Monoterpene |
Fresh, herbal, "haze" |
| β-caryophyllene |
Sesquiterpene |
Pepper, spice |
| Humulene |
Sesquiterpene |
Woody, hoppy |
| Total terpenes |
— |
~2% of flower weight on average |
What to do
- Read the terpene section of a certificate of analysis, not just THC.
- Dry slowly, about 18–21 °C (64–70 °F) and 55–62% RH for 7–14 days.
- Cure and store in full, airtight, dark jars; skip humidity packs, which rob terpenes.
- Pheno-hunt by nose and keep unusual profiles.
Common mistakes
- Assuming a terpene predicts an effect. Effects are reported, not promised.
- Fast, warm drying that drives off monoterpenes.
- Believing very high total-terpene claims without a lab name and date.
Terpenes are volatile hydrocarbon compounds built from five-carbon isoprene units; in cannabis they are made in the trichome heads and are a major part of aroma and flavour.Myrcene (beta-myrcene) is a monoterpene with a musky, earthy, ripe-fruit aroma and is the most common dominant terpene in commercial cannabis flower.Limonene is a monoterpene with a citrus aroma, found in citrus peel and many cannabis cultivars, where it is often among the top three terpenes.Beta-caryophyllene is a spicy, peppery sesquiterpene common in cannabis, notable as a dietary terpene that also binds the CB2 receptor in laboratory studies.Alpha-pinene is a bicyclic monoterpene with a sharp pine-resin aroma, the main terpene of conifer needles and a common, usually secondary, terpene in cannabis.Terpinolene is a monoterpene with a fresh, herbal, piney-citrus-floral aroma that dominates a distinctive, less common cannabis chemotype.A hair-like outgrowth of the plant's skin; in cannabis the glandular types make and store the resin holding cannabinoids and terpenes.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.A monoterpene is a ten-carbon terpene made from geranyl pyrophosphate, such as myrcene, limonene, pinene or terpinolene; they are the most volatile terpenes and the first lost in drying.A sesquiterpene is a fifteen-carbon terpene made from farnesyl pyrophosphate, such as beta-caryophyllene, humulene and bisabolol; they are heavier and less volatile than monoterpenes.Sulfur (S) is a secondary nutrient taken up as sulfate, used in the amino acids cysteine and methionine; deficiency yellows new growth fairly evenly.Cannabis irradiation is treating harvested flower with ionising radiation, gamma, electron beam or X-ray, to cut microbial counts; permission and labelling rules vary.A COA (certificate of analysis) is a lab's signed report of what it measured in a specific sample, such as cannabinoids, terpenes, moisture and contaminants, with methods and limits.THC (Δ9-tetrahydrocannabinol) is the neutral, decarboxylated cannabinoid mainly responsible for cannabis's reported intoxicating effects; the living plant makes it almost entirely as THCA.Relative humidity is the water vapour in air as a percentage of what it could hold at that temperature, so the same RH dries plants differently at different temperatures.A salt-solution sachet sold to hold a sealed container at a fixed relative humidity; GenetixBay regards them as a marketing gimmick that robs terpenes.
