Trichomes and Resin Glands: What They Are and What They Contain

What trichomes are

Trichomes are tiny structures on the surface of a plant. In cannabis, the glandular ones produce and store many of the plant's secondary metabolites (compounds that are not needed for basic growth), including cannabinoids and terpenes, in the female flowers. [1] They are the "resin glands" people refer to. This page describes them as plant biology. It does not give harvest-timing, growing or processing guidance. For the whole plant, see Cannabis Plant Anatomy.

Types plant scientists describe

A microscope study of high-THC cannabis flowers found two glandular trichome types: bulbous and capitate. Capitate trichomes (those with a rounded head) were either sessile (no stalk) or stalked. [2] In that study, stalk lengths ranged from 20 to 1,100 micrometers and glandular heads from 40 to 110 micrometers across. A micrometer is a thousandth of a millimeter, so these are very small structures. [2]

What they contain

A review of cannabis glandular trichomes says the stalked type produces resin containing cannabinoid acids such as THCA and CBDA, along with other secondary metabolites. [3] Terpenes are stored there too. [1] The acids are the plant's raw forms and are described in Decarboxylation Explained.

Resin

In the microscope study, resin appeared as droplets on the surface of the gland heads, and the droplets caused many heads to stick together or collapse. [2] The same study found that drying changed the look of the trichomes. [2] In everyday talk, "resin" can also mean a product made from the plant. Those product terms are handled separately in Rosin, Resin, Live Resin and Live Rosin and Hash and Kief, and in the Cannabis Glossary.

Trichomes differ by cultivar and plant age

In that study, trichome numbers, development and maturity depended on both the plant's genotype and its age, and not every trichome matured at the same time. [2] A 2025 study compared two modern cultivars with two traditional landraces and found the modern ones had larger trichomes with more secretory cells, alongside higher cannabinoid and terpene concentrations in the lab data. [1] This is a small plant-science study of four cultivars. It does not tell a consumer what any product contains or how it will feel.

Aging seen under a microscope

Under the microscope, researchers saw stalked glandular heads develop a brown color, lose some of their fluorescence under ultraviolet light, and eventually undergo senescence (aging) and dehiscence (splitting open or shedding). [2] These are laboratory observations in two genotypes. They are not a guide for judging any plant or product at home, and this site does not give harvest-timing advice. Scientists note that most attention in cannabis production goes to whole-flower yield, even though the trichomes are the source of the compounds of interest. [3]

What trichomes cannot tell you

The review authors note that scientific understanding of cannabis trichomes is still limited. [3] How a flower looks under magnification is not a measurement of its cannabinoid content. Measured values come from laboratory testing, covered in How to Read a Cannabis COA. Because composition varies, this site does not state typical percentages, and verified batch data would be needed for any specific product.

Safety note

NIDA notes that concentrated cannabis products can rapidly deliver large amounts of THC. [4] Children and pets can be harmed by swallowing any cannabis product. If you think a child has swallowed a cannabis product, FDA says to take the child to a physician or emergency department. [5] In the US, call 911 or Poison Help at 1-800-222-1222.