Types of Cannabis Morphology and Classification

Despite much genetic research Botanical Taxonomists have not come to a consensus on the classification of cannabis taxonomy. Are all plants belonging to the genus Cannabis mere varieties of a single species? Is it appropriate to use the labels Sativa, Indica, and Ruderalis to describe cannabis effects and potency? Historically, classification of cannabis has been based solely on phenotype. That is to say the physical chartachaeristics of a plant. Only in recent studies into the genotype expression (Genetic characteristics) and mapping of many varieties can we gain a larger perspective on cannabis classification and hybridization.


Discovery Of Cannabis

Swedish botanist and the "father of taxonomy" Carl Linnaeus first identified and catalogued the cannabis plant for the western world and publishing Cannabis sativa in his seminal Species Plantarum of 1753. The word Cannabis is derived from the greek word "Kannabis" meaning hemp.


Later in 1785 Jean-Baptiste Lamarck, was given some plant specimens collected in India. Characteristics including their firm stems, thin bark, and the shape of their leaves and flowers, led Lamarck to classify this subspecies as Cannabis Indica. It wasn't until 1924 that Russian Botanist D. E. Janischewsky identified a third cannabis type in southern Siberia he named C. Ruderalis. Ruderalis tends to occupy northern regions of the hemisphere, display lower levels of THC than C. Sativa or C. Indica. We now predominately identify C. Ruderalis as an Auto-flower. Meaning it is not dependent on photoperiods of light to induce flowering in the plant.


Cannabis is speculated to have first grown naturally in Central Asia and spread from that site of origin through human cultivation to South East Asia and west to Europe. Through trade and colonization cannabis then spread to Africa and eventually the Americas.


Indica V.s Sativa

Today the use of Sativa and Indica are widespread to describe the effects and the appearance of a plant. Indicas are considered to be shorter in stature, shorter flowering time, darker wider leaves and an effect that is more sedative and described as "body high". Sativas are described as taller, more lanky and with longer thin leaves and having a stimulating or cerebral effect when ingested or smoked. Most all cannabis strains on the market are described as being either sativa or indica dominant.


While the generalized terms Indica and Sativa may more often than not reflect some degree of accuracy in determining a plants genealogy and effects, the inherent complexity of cannabis demands that we classify cannabis by more meaningful attributes.


Dr. Ethan Russo. Medical Director of PHYTECS and former Senior Medical Advisor at GW Pharmaceuticals expressed his concern for the characterization of cannabis in an interview in 2016.


"There are biochemically distinct strains of Cannabis, but the sativa/indica distinction as commonly applied in the lay literature is total nonsense and an exercise in futility. One cannot in any way currently guess the biochemical content of a given Cannabis plant based on its height, branching, or leaf morphology. The degree of interbreeding/hybridization is such that only a biochemical assay tells a potential consumer or scientist what is really in the plant. It is essential that future commerce allows complete and accurate cannabinoid and terpenoid profiles to be available"


How Do We Classify Cannabis?

Cannabinoid profile, terpene profile, flowering time, growth habit, and effect are important to the grower and the consumer. It seems that humanity struggles to classify the wide diversity that comes as a result of our influence. Since it is almost always appropriate to call a dog a "mutt", i suppose referring to all cannabis as "hybrids" may be appropriate. The same way someone may generalize a breed as being 70% Husky and 30% Chow when all dogs are decedents of wolves. In reality no one classification can describe the evolution of a plant. With over 113 distinct cannabinoids and thousands of terpene combinations in the cannabis plant, the expressions are near limitless. We can however investigate genealogy and how that effects the chemotype (same morphological characteristics) of cannabis. Continued investigation into cultivars genealogy and how that effects morphology, and profile, will provide some details as to how me may classify cannabis in the future.


Study Shows Cannabis Profile More Closely Linked To Sativa-Indica Labeling Than Actual Lineage

In a study conducted by researchers at Dalhousie University analyzed over 100 cannabis and hemp samples comparing the reported lineage of the sample versus genotyped results. They showed a stronger correlation between reported genealogy and a few major terpenes and cannabinoids, than that of reported genealogy and genomic genealogy showed. The below graphs show both the genetic markers identified in single nucleotide polymorphisms and terpene results and the deviance away from the indica-sativa labeling. A clearer correlation and grouping is easily identified in cannabinoid and terpene profiles indicating that sativa-indica labeling is based more on physical attributes than actual lineage.

a, Genome-wide single nucleotide polymorphisms data. b, Terpenes and cannabinoids. Each dot represents a Cannabis sample and is colored by the labelling scale ranging from 100% Sativa to 100% Indica. c, The percent variance explained by PCs from the genome-wide SNP data (blue), from the terpene and cannabinoid data (green) and from both the genetic and chemical data (purple). The y axis shows the percent variance explained as PCs are added to linear models where the Sativa–Indica labelling scale is the dependent variable. (3)


Dr. Russo: "We would all prefer simple nostrums to explain complex systems, but this is futile and even potentially dangerous in the context of a psychoactive drug such as Cannabis. Once again, it is necessary to quantify the biochemical components of a given Cannabis strain and correlate these with the observed effects in real patients. Beyond the increasing number of CBD predominant strains in recent years, almost all Cannabis on the market has been from high-THC strains. The differences in observed effects in Cannabis are then due to their terpenoid content, which is rarely assayed, let alone reported to potential consumers. The sedation of the so-called indica strains is falsely attributed to CBD content when, in fact, CBD is stimulating in low and moderate doses! Rather, sedation in most common Cannabis strains is attributable to their myrcene content, a monoterpene with a strongly sedative couch-lock effect that resembles a narcotic. In contrast, a high limonene content (common to citrus peels) will be uplifting on mood, while the presence of the relatively rare terpene in Cannabis, alpha-pinene, can effectively reduce or eliminate the short-term memory impairment classically induced by THC." (1)


Cannabis Chemotypes And Chemovars

Cannabis categorization and nomenclature is changing. The standard categorization of strain name is becoming outdated. A same name strain can always have many different expressions and effects from one grower to another. This approach is being replaced by more accurate and flexible terms. Chemotypes are types of cannabis that are grouped by their most produced cannabinoid. For example, Type 3 cannabis is CBD dominant. Chemovars are types of cannabis which are loosely defined and grouped, based on at least one or two of the most abundant cannabinoids and two-to-four main terpenes and a further sub-classification. Chemotypes outside of cannabis are classified by their most useful constituent. For example two separate chemotypes of lavender may be distinguished using their most abundant terpene. Pacific Blue is a linalool chemotype, 38% and Avice Hill is a linalyl acetate chemotype, averaging about 40%. As cannabis contain many compounds to consider further sub devisions into chemotypes is necessary.


With public acceptance and knowledge of the wider chemical profile of cannabis, physicians and personal users could extrapolate much more practical information, including what types of cannabis are better for which ailments, and how different chemical profiles influence the body.


In a 1973 paper published in Nature Magazine Ernest Small and H.D. Beckstead introduced the idea of categorizing cannabis according to cannabinoid content. (4) This approach has been adopted by many in the industry today.


Type I is THC dominant and is an intoxicant. It is the most common cannabis on the market and has a long history of use. Modern varieties can contain as much as 30% THC.


Type II cannabis is defined by a mixed ratio of THC and CBD. CBD is known to mitigate unwanted toxicity from THC by modulating the effect of CB1 and CB2 Receptors in the body.


Type III is CBD dominant and is non intoxicating. It contains below 1% THC and is popular for tinctures slaves and topical products that are known to modulate endogenous cannabinoids and hemp maintain homeostasis in the body.


Type IV is CBG dominant. CBG in non intoxicating and has demonstrated potential therapeutic benefits ranging from appetite stimulation to reduction in neuroinflammation.


Type V produces little to no cannabinoid content at all and is used mostly for fiber, seeds, and textiles.


Cannabis Samples Show Three Distinct Types Clusters in a graph
Cannabis Samples Show Three Distinct Types Clusters




(1) Piomelli D, Russo EB. The Cannabis sativa Versus Cannabis indica Debate: An Interview with Ethan Russo, MD. Cannabis Cannabinoid Res. 2016 Jan 1;1(1):44-46. doi: 10.1089/can.2015.29003.ebr. PMID: 28861479; PMCID: PMC5576603.


(2) Watts G. Cannabis confusions. BMJ. 2006 Jan 21;332(7534):175-6. doi: 10.1136/bmj.332.7534.175. PMID: 16424501; PMCID: PMC1336775.


(3) Watts, Sophie & McElroy, Michel & Migicovsky, Zoë & Maassen, Hugo & Velzen, Robin & Myles, Sean. (2021). Cannabis labelling is associated with genetic variation in terpene synthase genes. Nature Plants. 7. 1330-1334. 10.1038/s41477-021-01003-y.


(4) A Practical and Natural Taxonomy for Cannabis Author(s): Ernest Small and Arthur Cronquist Source: Taxon, Vol. 25, No. 4 (Aug., 1976), pp. 405-435 Published by: Wiley Stable URL: https://www.jstor.org/stable/1220524

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