Taxonomy

The taxonomy of cannabis plants has been debated for over two centuries. In 1753, Carl Linnaeus first identified the genus cannabis sativa L.—the “L” referring to his last name—with only one species: cannabis sativa. Cannabis sativa referred to the non-psychoactive cannabis plant cultivated for its oil-rich seeds and fibrous stalks, or what is known today as “hemp.”

Jean-Baptiste Lamarck then identified “cannabis indica” in 1785, a species of cannabis grown for its psychoactive resin filled with delta-9-tetrahydrocannabinol (d9THC), what is called “marijuana” today. D. E. Janischevisky later identified “cannabis ruderalis” in 1925, an indigenous species of hemp found in regions of Russia.

Debate abounds about whether these are separate species or a single species with multiple varieties. Regardless of the academic debate about cannabis classification, most laws adhere to the single species model because of its ease for regulatory purposes. For instance, international organizations such as the United Nations and the World Health Organization now promulgate the single species model for cannabis. This is, in part, why the criminalization of marijuana has also criminalized hemp: if you outlaw “cannabis,” then all plants in that genus—no matter their psychoactive properties—are illegal.

What’s more, historical records on cannabis plants tend to use names for the plants interchangeably, or sometimes without enough information to determine whether it is hemp or marijuana.

Consider, for example, these two illustrations of cannabis plants. The first illustration depicts “Cannabis Sativa, L.” (above) from The Western Druggist in April 1899. The illustration likely depicts the non-psychoactive hemp plant, but if cannabis sativa L. refers to the genus rather than species, then it could be either hemp or marijuana without any further classification.

The other entry (below) comes from The Romance of Empire Drugs, a guide to herbs, fruits, and roots used in medicine and pharmacy. The illustration identifies the plant as “Cannabis Sativa, LINN” and further specifies it as “C. Indica Lam,” indicating that it depicts marijuana, the psychoactive subspecies of cannabis.

The record of cannabis migration, however, sheds some light on how cannabis plants developed, interbred, and became used for specific purposes. The general consensus is that cannabis plants were first found in central Asia as early as 12,000 BCE and migrated west across trade routes before they landed in eastern Europe. From there, cannabis plants were transported into Africa as well as across the Atlantic into the Americas.

Even though the migratory histories of hemp and marijuana are not identical, the cultivation and interbreeding of cannabis plants means that they cannot be easily separated. As marijuana and hemp migrated to new regions, both adapted to the local environment and displayed physical and chemical variations (i.e. height of plant, strength of fiber, space between leaves, bud structure, etc.). New varieties of cannabis arose with different properties as the plants migrated, interbred, and were cultivated.

Check out below the encyclopedic entries for American, African, and Indian cannabis from Squibb's Atlas of Official Drugs published in 1919. All three varieties are considered part of “Cannabis Sativa.” The difference is that American cannabis is considered “cannabis sativa Linné,” meaning hemp, while Indian cannabis and African cannabis are both indica subspecies, meaning marijuana. However, none of the entries describe the plant as psychoactive, even when named as “ganja.”

Today, matters are complicated further by contemporary growing practices where marijuana cultivators hybridize cannabis plants, give them popular names (like “Aghani,” “OG Kush,” “Dutch Treat,” etc.), and advertise them on a spectrum from sativa (energizing) to indica (sedating) with innumerable hybrids in between.

The colloquial use of “sativa” and “indica” by marijuana cultivators and sellers, however, describes the perceived effects of the marijuana strain, rather than the taxonomic difference. All marijuana strains that are marketed as sativa or hybrid still come from the indica subspecies of cannabis that produce d9THC-rich resin.

The most clear delineation between cannabis plants is whether or not they produce d9THC levels above 0.3% or not: cannabis plants above 0.3% d9THC are considered marijuana and those below are considered hemp. A 2011 study published in Genome Biology analyzed the genetics from a popular marijuana strain (“Purple Kush”) and a popular hemp strain (“Finola") and compared the results.

The researchers concluded that the production of d9THC in marijuana comes down to a specific gene that encodes proteins: delta-9-tetrahydrocannabinolic acid synthase. This gene is what helps marijuana produce d9THC during the plant development stage. The researchers suggest that their study supports a meaningful difference between hemp and marijuana but still supports a single species model. To keep matters clear throughout this exhibit, marijuana and hemp will be used instead of specific taxonomic names.

Further Reading

Booth, Martin. Cannabis: A History. MacMillan, 2005.

van Bakel, Harm et al. “The Draft Genome and Transcriptome of Cannabis Sativa.” Genome Biology, vol. 12, 2011, pp. 1-17.

Duval, Chris. The African Roots of Marijuana. Duke University Press, 2019. 

Hillig, Carl. “Genetic Evidence for Speciation in Cannabis.” Genetic Resources and Crop Evolution, vol. 52, 2005, pp. 161-180.

Small, Ernest and Arthur Cronquist. “A Practical and Natural Taxonomy for Cannabis.” Taxon, vol. 25, no. 4, 1976, pp. 405-435.

Warf, Barney. “High Points: An Historical Geography of Cannabis.” Geographical Review, vol. 104, no. 4, 2014, pp. 414-438.