Chemotype
Plant classification by cannabinoid ratio, not genetics or morphology.
Chemotype is one of the few cannabis classification systems that maps cleanly onto chemistry. Knowing whether a plant is THC-dominant, CBD-dominant or mixed tells you something real about its effects. But it says nothing about terpenes, minor cannabinoids, or the folklore claims about strain names predicting 'sedation' or 'energy.' It's useful for growers and medical prescribing—just not a complete story.
Definition
A chemotype (from chemo- + type) is a classification of a plant based on the chemicals it produces, rather than its appearance or genetic lineage. In cannabis, it almost always refers to the ratio of the two dominant cannabinoids, THC and CBD, measured in dried flower [1][2]. The term chemovar (chemical variety) is sometimes used interchangeably, though some authors reserve it for finer-grained profiles that also include minor cannabinoids and terpenes [3].
The five standard types
The modern chemotype system originates with Ernest Small and H.D. Beckstead's 1973 chemotaxonomy of Cannabis [1], later refined by de Meijer, Mandolino and others [2][4]:
- Type I — THC-dominant (high THC, low CBD). Most common in recreational and modern high-THC cultivars.
- Type II — Mixed (roughly balanced THC and CBD). Common in medical cultivars and some older landraces.
- Type III — CBD-dominant (high CBD, low THC). Includes most industrial hemp and high-CBD medical strains.
- Type IV — CBG-dominant (rare; the plant fails to efficiently convert CBG into THC or CBD) [4].
- Type V — Essentially cannabinoid-free (described in some fiber hemp lines) [2].
The ratio is controlled largely by alleles at a single locus encoding the enzymes that convert CBGA into either THCA or CBDA [2][4].
What chemotype tells you
Chemotype reliably predicts the major cannabinoid output of a plant, which in turn predicts core pharmacology: whether a product will be strongly intoxicating (Type I), mixed (Type II), or largely non-intoxicating (Type III) Strong evidence[1][2]. This makes it useful for both growers selecting for desired cannabinoid profiles and medical practitioners prescribing based on THC and CBD content [3].
What chemotype does not tell you
Chemotype (in the classic THC:CBD ratio sense) says nothing about:
- Terpene profile — two Type I plants can smell and taste quite different, despite identical THC and CBD ratios.
- Minor cannabinoids like CBN, CBC, THCV or others.
- Effects beyond intoxication level — the common claim that strain names predict 'sedation' or 'energy' remains folklore unsupported by controlled trials Disputed[3].
- Growth traits, yield, pest resistance, or plant morphology.
This is why some researchers advocate for expanded 'chemovar' profiles that include terpene and minor cannabinoid data alongside the THC:CBD ratio [3].
How it is used
Chemotype classification is standard in cannabis breeding, seed catalogues, and laboratory cannabinoid testing. Growers use it to select plants for desired cannabinoid profiles. Medical-use jurisdictions rely on it as a basic framework for product categorization and patient selection, though actual prescribing often incorporates terpene and minor cannabinoid data from laboratory analysis [2][3].
Sources
- Peer-reviewed Small, E., & Beckstead, H. D. (1973). Common cannabinoid phenotypes in 350 stocks of Cannabis. Lloydia, 36(2), 144–165.
- Peer-reviewed de Meijer, E. P. M., Bagatta, M., Carboni, A., Crucitti, P., Moliterni, V. M. C., Ranalli, P., & Mandolino, G. (2003). The inheritance of chemical phenotype in Cannabis sativa L. Genetics, 163(1), 335–346.
- Peer-reviewed Lewis, M. A., Russo, E. B., & Smith, K. M. (2018). Pharmacological foundations of cannabis chemovars. Planta Medica, 84(4), 225–233.
- Peer-reviewed Mandolino, G., & Carboni, A. (2004). Potential of marker-assisted selection in hemp genetic improvement. Euphytica, 140(1-2), 107–120.
How this page was made
Generation history
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Related
- Type I Chemotype (THC-Dominant) — High-THC, low-CBD cannabis defined by cannabinoid genetics and enzyme function.
- Type II Chemotype (Mixed THC/CBD Cannabis) — Cannabis plants with roughly equal THC and CBD, determined by genetics at the cannabinoid...