Cannabis trichomes are the microscopic resin glands behind the frosty, sugar-dusted look of well-grown flower. They aren't decoration. Trichomes are where the plant makes and stores its cannabinoids, including THCA, along with most of the terpenes behind its aroma. Here's what they are, the main types, how growers read them at harvest and how they become kief and hash.
What cannabis trichomes are and why plants make them
What are trichomes, exactly? A trichome is a small outgrowth on a plant's surface. In cannabis, the ones that matter most are glandular trichomes, which produce resin. On a female plant, the stalked glandular trichomes cluster on the calyxes and bracts of the flowers and spill onto the sugar leaves around them. Male plants make only small amounts of cannabinoids, so growers focus on female flowers. Our plant anatomy guide shows where those parts are.
Why does the plant bother? The clues point to defense: THC may help shield the plant from ultraviolet light, and some terpenes repel insects. Sealing these compounds inside a gland also protects the plant, since THCA can be toxic to plant cells.
Types of trichomes: bulbous, sessile and stalked
Scientists sorted the glandular trichomes on cannabis flowers into three types in the 1970s, using an electron microscope. They differ mostly in size and in whether the head sits on a stalk.
| Type | Shape | What to know |
|---|---|---|
| Bulbous | Tiny and low to the surface | The smallest of the three |
| Capitate-sessile | A round head on a very short stalk | Most common early in flowering |
| Capitate-stalked | A larger head on a long stalk | Produces the most cannabinoids and most of the visible frost |
In a microscope study of two high-THC strains, glandular heads measured 40 to 110 micrometers across, and stalks ranged from 20 to 1,100 micrometers long. Other researchers found that capitate-stalked trichomes appear to grow from sessile-looking ones as the flower matures.
Inside the gland: how trichomes make cannabinoids and terpenes
Each glandular head works like a tiny factory. Secretory disc cells at its base build cannabinoids, terpenes and flavonoids, and the finished compounds collect in a cavity just under the head's outer skin.
The plant makes cannabinoids in acid form, so fresh flower holds mostly THCA and CBDA rather than THC and CBD. Heat converts the acids, which is why smoking, vaping and baking activate THC. Slower conversion also happens in storage, and its pace depends mainly on temperature and light.
Chemistry shifts with maturity, too: stalked trichomes lean toward lighter, more volatile terpenes called monoterpenes, while sessile ones carry a different mix.
Trichome color at harvest: clear, cloudy, amber
Under a jeweler's loupe, trichome heads change color as the flower ripens. The resin cavity starts out clear, turns milky white and can end up amber to dark brown as the head ages. Many growers use that shift to time the harvest:
- Clear: the flower is still developing.
- Cloudy or milky: many growers aim to harvest in this window.
- Amber: heads are aging, and some growers wait for a share of amber before they cut.
This is a grower's habit, not settled science. Trichomes on one bud don't all mature at once, and strain and plant age change the pace, so a color check is an estimate. You'll also hear that amber trichomes make for a more sedating high. Some THC does break down into CBN as cannabis ages, but the idea that amber heads change the high is grower lore, not a proven effect.
Collecting trichomes: dry sift, ice-water hash, kief and extraction
Nearly every concentrate starts by separating trichomes from the plant.
- Kief. Loose trichome heads that shake off dried flower and collect under a grinder's screen. Our guide to what kief is covers how people use it.
- Dry sift. Dried flower is rubbed or tumbled over a series of fine screens that sort the heads by size. The cleanest grades are mostly trichome heads, with little plant material.
- Ice-water hash. Buds or trim get agitated in icy water, which makes the heads brittle enough to snap off. The resin is filtered through mesh bags and dried, and pressing it with gentle heat makes rosin.
- Solvent extraction. Butane, propane, ethanol or CO2 dissolves the resin, and the solvent is then removed. Our overview of types of cannabis extraction explains each method.
Some makers freeze plants right after harvest to keep more of the fresh terpenes, the idea behind the products we compare in live resin vs. live rosin.
Trichomes and potency: what frost means when you shop
Frost isn't proof of potency. A heavy coat of trichomes looks impressive, and many shoppers read it as strength. A 2025 review found that trichome density alone doesn't reliably predict cannabinoid content, because trichome shape, size and maturity matter too. The lab-tested numbers tell you more, and a Michigan label shows the THC and CBD content plus the harvest date.
Handle buds gently. Trichome heads are fragile. Rough handling and drying change their shape, and every squeeze knocks some resin loose.
Store flower to protect the resin. Heat and light speed up the chemical changes inside trichomes. Keep flower sealed airtight and stored in a cool, dark spot. Our guide on how to store cannabis has the details.
The products in our stores come from trusted vendors and have passed Michigan's required testing. Browse flower on your store's menu to compare lab-tested THC, or ask our budtenders to help in person. Recreational shopping is available to adults 21 and older. Enjoy cannabis responsibly.
