What is the difference between a strain and a cultivar?

Q: What is the difference between a strain and a cultivar?

A cultivar is a formal botanical term: a cultivated plant group that is distinct, uniform and stable when propagated, by seed or cuttings. A strain is the popular cannabis word, used loosely for anything from one clone to a brand name. A chemovar is a cultivar defined by its chemistry. Genetic studies show many strain names don't reliably mean one genotype.

Short answer

A cultivar is the botanical term for a cultivated plant group that is distinct, uniform and stable when propagated. "Strain" is the popular cannabis word, used for anything from a single clone to a marketing name. A chemovar is a cultivar defined by its chemistry. Established terminology.

Why

"Cultivar" has rules. The International Code of Nomenclature for Cultivated Plants sets how cultivars are defined and named ^[1]. A clonal cultivar is one genotype; a seed cultivar must come true from seed.

"Strain" has none. It's borrowed from microbiology and applied loosely. Genetic testing of retail cannabis found genetic outliers within most same-named strains ^[3], so a strain name is a claim, not an identity.

"Chemovar" describes what's in the jar. Researchers argued that medicinal cannabis should be classified by its chemical profile, because names don't predict chemistry ^[2]. Large lab datasets confirm that commercial labels align poorly with chemotype, though some names are consistent ^[4].

The numbers

Term	Defined by	Example of correct use
Cultivar	Distinct, uniform, stable traits (ICNCP) ^[1]	A clone-only cut; a true-breeding seed line
Strain	Popular usage, no rules	Any named cannabis on a menu
Chemovar	Cannabinoid and terpene profile ^[2]	"THC-dominant, caryophyllene–limonene"
Phenotype	One plant's observed traits	The keeper from a pheno hunt

What to do

Treat a strain name as a claim; ask for the source and grow-out records.
For a clone, ask for chain of custody.
Choose by chemistry: read the cannabinoid and terpene sections of the certificate of analysis.
Call a one-off hybrid cross a cross, not a cultivar, until it breeds true.

Common mistakes

Assuming two plants with the same name are the same genotype.
Calling every seed pack a stable cultivar.
Treating "indica" or "sativa" on a label as a chemovar.

Full article: Why strain names are unreliable
Answers: what terpenes are · hemp vs marijuana
Article: Same cut, a thousand names
Terms: cultivar · strain · chemovar

A chemovar is a cultivar defined and named by its chemical profile, chiefly cannabinoids and terpenes, rather than by its appearance or a market strain name.The genotype is the set of alleles a plant actually carries, either at one locus or across its whole genome, as opposed to the traits you can see.Genotyping is reading a plant's DNA at selected markers to identify it, compare it with other plants, check sex or chemotype, or estimate its ancestry.Medical and adult-use cannabis are separate legal channels: medical access depends on authorisation by a health professional, adult-use on age alone.A chemotype is a plant's chemical phenotype, in cannabis usually its dominant cannabinoid class: THC-dominant (I), mixed (II), CBD-dominant (III), CBG-dominant (IV) or cannabinoid-free (V).A clone-only is a cultivar that exists only as cuttings from one original plant, with no seed line that reliably reproduces it.A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.A terpene profile is the measured mix of terpenes in a sample, reported as each compound's % w/w and the total, used to describe and compare cultivar aroma chemistry.Beta-caryophyllene is a spicy, peppery sesquiterpene common in cannabis, notable as a dietary terpene that also binds the CB2 receptor in laboratory studies.Limonene is a monoterpene with a citrus aroma, found in citrus peel and many cannabis cultivars, where it is often among the top three terpenes.The phenotype is what a plant visibly and measurably is (shape, colour, smell, chemistry, timing), the result of its genotype acting in a particular environment.In grower slang, a pheno is one individual plant from a seed lot, usually numbered during a hunt, as in "the #4 pheno".Terpenes are volatile hydrocarbon compounds built from five-carbon isoprene units; in cannabis they are made in the trichome heads and are a major part of aroma and flavour.A COA (certificate of analysis) is a lab's signed report of what it measured in a specific sample, such as cannabinoids, terpenes, moisture and contaminants, with methods and limits.A true-breeding line produces offspring that consistently look like the parents for a given trait, because the plants are homozygous for the alleles behind it.

Follow-up questions

What is a chemovar?

A chemovar is a chemical variety: a cannabis cultivar or group defined by its chemical profile, mainly its cannabinoids and dominant terpenes, rather than by name or shape. Researchers proposed classifying medicinal cannabis this way because names and 'indica' or 'sativa' labels don't predict chemistry. On a certificate of analysis, the chemovar is what the numbers show.

Is a clone-only a cultivar?

Yes, a clone-only is a clonal cultivar: one genotype kept alive by cuttings, so every plant of it is genetically identical apart from rare mutations and pathogens. Its name only means that genotype if the chain of custody is sound. Cuts get renamed and mixed up, so the same name from two sources can be two different plants.

Is a seed strain a cultivar?

A seed strain is a cultivar only if it breeds true for its key traits: distinct, uniform and stable from seed. Many seed releases are one-off crosses of two hybrids, whose seedlings vary widely, so strictly they are not yet cultivars. An inbred line (IBL) or a well-stabilised seed line can qualify.

Sources

Brickell CD, et al. (eds). 2016. International Code of Nomenclature for Cultivated Plants, 9th edition. Scripta Horticulturae 18. ISHS. ishs.org/scripta-horticulturae/international-code-nomenclatu

Hazekamp A, Fischedick JT. 2012. Cannabis: from cultivar to chemovar. Drug Testing and Analysis 4(7-8):660-667. doi.org/10.1002/dta.407

Schwabe AL, McGlaughlin ME. 2019. Genetic tools weed out misconceptions of strain reliability in Cannabis sativa: implications for a budding industry. Journal of Cannabis Research 1:3. doi.org/10.1186/s42238-019-0001-1

Smith CJ, Vergara D, Keegan B, Jikomes N. 2022. The phytochemical diversity of commercial Cannabis in the United States. PLoS ONE 17(5):e0267498. doi.org/10.1371/journal.pone.0267498