Trichomes are tiny hair-like growths on a cannabis plant. The glandular ones, stalks topped by a round resin head about 40 to 110 microns across, make and store the plant’s cannabinoids and terpenes. They grow most densely on the flowers, they turn from clear to cloudy to amber as they age, and hash is simply those heads, collected.
What are trichomes?
Trichomes are the tiny outgrowths that cover much of a cannabis plant, and the ones that matter are the glandular kind. A 2021 review from McGill University describes cannabinoids and terpenes forming in a ring of secretory cells at the base of each glandular head and collecting in a cavity under its outer skin. To the eye they look like frost; up close, the biggest look like tiny mushrooms.
Trichome types
Trichome types on a cannabis flower, with sizes from a 2023 microscope study by Zamir Punja and colleagues at Simon Fraser University:
| Type | What it looks like | What it does |
|---|---|---|
| Stalked glandular | A head 40 to 110 µm across on a stalk up to about 1 mm tall | Holds most of the resin; the hash maker’s target |
| Sessile glandular | A head sitting on the surface with no stalk | Makes resin too, and may be an early stage of the stalked kind |
| Bulbous | A tiny head, 15 to 30 µm, on a short stalk | Small and scattered |
| Non-glandular hairs | Pointed hairs with no head | No resin; the plant matter hash makers try to leave behind |
Where cannabis trichomes grow
Cannabis trichomes grow thickest on the flowers. The study found the stalked kind mostly on the bracts, the little leaves wrapped around each flower, while the leaves and stems carry sessile glands and plain hairs. The small sugar leaves inside the bud are frosted too, which is why hash is made from flowers and trim, not the big fan leaves.
How trichomes change as they ripen
Trichomes change as they ripen, in stages you can see. Early in flowering the sessile kind dominates; within a few weeks the stalked heads take over. The heads start clear, turn cloudy, then amber, a browning the researchers put down to oxidation inside the head. At the end, resin seeps out through the skin, heads stick together, shrink, collapse and fall off. Under ultraviolet light the stalked heads glow blue, researchers at the University of British Columbia found, and the 2023 study saw that glow fade as the heads aged.
Why trichomes matter to hash makers
Trichomes matter to hash makers because hash is nothing but trichome heads. Every method, from dry sift to ice water, aims to snap the heads off their stalks and keep the plant behind, and the heads’ size, about 40 to 110 microns, is why the filter bags are sized as they are: see bubble hash micron sizes. Inside those heads are the terpenes that give each hash its smell.
From the archive: Bubbleman on trichomes
From the archive, Bubbleman on trichomes in his own words, from two live Sunday shows. Tap a time to hear that moment.
Cannabis is a very unique plant. The fact that it’s producing as much of these compounds as it is, is pretty spectacular when you think about it. You don’t see too many plants in nature that are like the laboratory that is the glandular trichome from the cannabis plant.
On the trichome as a laboratory
Season 12, Episode 14, Skully Vibes draws live
When you find the ones that can, it’s quite a thing, and they just preserve themselves so perfectly in their own little resin heads. All you have to do is isolate them out.
On plants that make good hash
How to see trichomes
To see trichomes you need magnification: a jeweler’s loupe or a pocket microscope shows the heads and their color, and a macro lens shows them in full detail. Bubbleman has photographed them that way since 2008. Under ultraviolet light the stalked heads glow blue, which researchers think could one day help time the harvest.
Trichome guides
Trichome guides, for reading them at harvest:
Trichome questions
Trichome questions, answered short:
What are trichomes?
Trichomes are tiny hair-like growths on cannabis; the glandular ones carry round resin heads that make and store the plant’s cannabinoids and terpenes.
What do trichomes do?
Trichomes make and hold the plant’s resin, its cannabinoids and terpenes, in their glandular heads.
What are the types of trichomes?
The types of trichomes on cannabis are stalked glandular, sessile glandular and bulbous trichomes, plus non-glandular hairs that carry no resin.
What is a glandular trichome?
A glandular trichome is a trichome topped with a resin head, such as the stalked and sessile kinds, and that head is where the plant makes and stores its cannabinoids and terpenes. Bubbleman calls it a laboratory.
How big are trichome heads?
Trichome heads on the big stalked glands are about 40 to 110 microns across, on stalks that can reach about a millimeter tall.
Where are trichomes found?
Trichomes are found most densely on the flowers, especially the small bracts around each flower and the sugar leaves inside the bud.
Is it trichome or trichrome?
It is trichome; trichrome is a common misspelling, and as Bubbleman found when he started researching, searching for it turns up little.
Sources for this guide to trichomes
Sources for this guide to trichomes:
- Glandular trichome development, morphology, and maturation are influenced by plant age and genotype (Punja, Sutton and Kim, 2023), Journal of Cannabis Research
- Cannabis glandular trichomes: a cellular metabolite factory (Tanney and others, 2021), Frontiers in Plant Science
- Cannabis glandular trichomes alter morphology and metabolite content during flower maturation (Livingston and others, 2020), The Plant Journal
- The frostier the flower, the more potent the cannabis, University of British Columbia
- 2008 macro photographs, Bubbleman’s World on YouTube
- Hash Church Season 12, Episode 20: Bubbleman on learning the words glandular trichome, Buzzsprout
- Hash Church Season 12, Episodes 14 and 30: Bubbleman on trichomes, linked above