A trichome is any hair or outgrowth from the epidermis of a plant. Cannabis has two broad groups. Non-glandular trichomes are simple pointed hairs that protect the surface. Glandular trichomes are secretory: a disc of cells makes resin rich in cannabinoid acids (such as THCA and CBDA) and terpenes and stores it in a cavity under a waxy cuticle at the gland head.
In practice
The three glandular types are bulbous (tiny), capitate-sessile (on leaves and early flowers) and capitate-stalked (the mushroom-shaped glands on bracts that hold most of the resin). When growers say "frost", "crystals" or "trichomes", they almost always mean capitate-stalked heads.
With a 60-100x loupe or microscope, head colour shows maturity: clear, then cloudy (milky), then amber. GenetixBay's harvest guidance is a matter of taste, ideally a mix of a few clear, mostly cloudy and some amber heads.
Trichome heads are fragile. Rough handling, warm temperatures and agitation knock them off, which matters for trimming and storage.
Don't confuse with
- Pistil (stigma): the white or orange hairs of the flower, not resin glands.
- Kief: loose detached trichome heads, a processing term.
- Powdery mildew: a fungal coating that sits flat on leaf surfaces, not on stalks.
Myth check
Frost is not potency. Visible trichome density did not reliably predict THC in field work, and bag appeal is not quality (Supported). See Mythbusters.
A non-glandular, claw-shaped hair on cannabis leaves that contains a calcium carbonate crystal (cystolith); it makes no resin.The female reproductive organ of a flower (ovary, style and stigmas); in cannabis growers loosely call the visible white stigmas "pistils".THCA (tetrahydrocannabinolic acid) is the acid cannabinoid that drug-type cannabis makes in its trichomes; heat or time decarboxylates it into THC, losing about 12% of its mass.The large mushroom-shaped glandular trichome on cannabis bracts, with a multicellular stalk and a resin-filled head; it holds most of the flower's cannabinoids and terpenes.Trichome heads are the bulbous resin-filled tops of capitate glandular trichomes, where cannabis makes and stores nearly all its cannabinoids and terpenes; they are the raw material of hash.A fungal disease, on cannabis caused mainly by Golovinomyces ambrosiae, that grows as white powdery patches on leaves and buds and thrives in moderate humidity.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.Bag appeal is how good flower looks in the bag or jar, frost, colour, density and trim, which sells cannabis but does not measure its quality.A glandular trichome with a resin head but little or no stalk, sitting close to the surface of leaves and young bracts.The smallest glandular trichome on cannabis, a few cells with a tiny head (about 10-30 µm), scattered over leaves and stems.The maturity of glandular trichome heads, read by colour under magnification: clear (immature), cloudy or milky (mature), then amber (ageing).
