The smell is the first thing you notice when you open a jar. That blend of citrus, pine or damp earth doesn’t come from THC or CBD, which are odourless: it comes from the terpenes.
What is a terpene?
Terpenes are volatile aromatic compounds produced by the plant in the same glands where cannabinoids are formed: the trichomes. They are not unique to cannabis: limonene is found in lemon peel, pinene in pine needles and linalool in lavender. In the plant, they serve a practical function: attracting some insects whilst repelling others.
Over a hundred different terpenes have been identified in cannabis, although in practice just half a dozen account for most of what we perceive when we smell a flower.
The six you’ll recognise straight away
- Myrcene. Earthy, with undertones reminiscent of ripe mango. It is the most abundant terpene in many strains.
- Limonene. Citrusy and tangy – just like the scent you get when you grate an orange.
- Pineno. Resinous, like a coniferous forest. It is one of the most common terpenes found in nature.
- Linalool. Floral and delicate, strongly reminiscent of lavender.
- Caryophyllene. Spicy, with a hint of black pepper or clove.
- Terpinolene. More difficult to describe: herbal, with sweet and green apple notes.
Why do two varieties smell so different?
What we call the aroma of a strain is actually a ratio. It is not that one variety contains limonene and another does not, but rather that the mixture and relative quantities vary, and with them the profile perceived by the nose. That ratio depends on genetics, but also on how the plant was grown, when it was harvested and the subsequent curing process.
That is why two samples of the same variety, grown by different people, can smell quite different.
The heat and the weather take them away
Terpenes are volatile, which is precisely what makes them detectable: they evaporate easily. Each one has a different boiling point, and they are all sensitive to temperature, light and the passage of time.
This has a practical implication. A well-preserved flower retains its fragrance for months; the same flower, placed in a plastic bag, exposed to the sun and subject to temperature fluctuations, loses its fragrance within weeks.
Training your nose
Recognising terpenes is a matter of practice, not talent. Here are a couple of tips that work:
- Smell it before grinding it. The whole flower releases its aroma gradually; once ground, it dissipates quickly.
- Compare two varieties back-to-back rather than smelling just one. The contrast reveals much more than the smell on its own.
- Clear your nose between each one. Thirty seconds of breathing in fresh air is enough to reset.
- Put it into words. Saying that something reminds you of a pine tree helps you remember it much better than simply noting that it has a strong smell.
A hypothesis, not a fact
You’ve no doubt heard of the entourage effect – the idea that terpenes and cannabinoids interact with one another and modulate the final effect. It’s a reasonable hypothesis and research is ongoing, but it’s best to treat it for what it is: an open line of inquiry, not something that has been proven.
One thing is certain: the aroma is part of the experience, and learning to distinguish it makes choosing a much more interesting process.
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