Which factors affect cannabis potency?


Plant part used


Product type


Cultivation methods







Plant part used

The secretion of THC is most abundant in the flowering heads and surrounding leaves of the cannabis plant.

The amount of resin secreted is influenced by environmental conditions during growth (light, temperature, and humidity), sex of the plant and time of harvest.

The THC content varies in the different parts of the plant: from 10-12 percent in flowers, 1-2 percent in leaves, 0.1-0.3 percent in stalks, to less than 0.03 per cent in the roots.

Cannabinoids are secondary metabolites not critical for survival. The plant by a combination of fats, carbs, proteins, vitamins, various metabolites, and minerals. As a result, the plant does not have a natural reason to produce more than 25-30 percent total cannabinoids.



Product type

There are three main types of cannabis products: herb (marijuana), resin (hashish) and oil (hash oil).

Cannabis herb comprises the dried and crushed flower heads and surrounding leaves. However, sinsemilla, derived from the unfertilized female plant, can be much more potent.

Cannabis resin can contain on average about 20 to 28 percent THC content.

The most potent form of cannabis is cannabis oil, derived from the concentrated resin extract. It may contain more than 60 percent THC content.



Cultivation methods

The cannabis plant grows in a variety of climates.

The amount and quality of the resin produced depends on the temperature, humidity, light and soil acidity/ alkalinity.

Accordingly, herbal cannabis grown outdoors varies considerably in potency.

Intensive indoor cultivation of female plants and clones, grown under artificial light, often without soil (using hydroponic cultivation) and with optimized cultivation conditions, produces cannabis of a consistently higher potency.




Most data on cannabis potency are derived from the analysis of samples.

This means that those samples must be representative so that inferences and extrapolations can be made.

An unrepresentative sample can give incorrect or misleading results.




THC is converted to cannabinol on exposure to air and light.

This process reduces the THC concentration, especially in old samples which have not been stored under suitable conditions (that is, a cool, dark place).