Since the mid-1970s, when large-scale commercial growing of cannabis began again in Europe and North America, it has been usual to classify cannabis plants as either Cannabis sativa (‘cultivated’) or Cannabis indica (‘Indian’). Although the wild, Central Asian variety known as Cannabis ruderalis (‘roadside’) is sometimes mentioned as an ancestor plant in descriptions by cannabis breeders, the two-fold cannabis sativa vs cannabis indica classification is the general norm. This is reflected in the numerous publications that detail cannabis plant varieties.
A growers’ guide by Albie (2005), a typical example among many similar publications, describes forty-one varieties, both sativa and indica. Seedsman.com provides the seeds of over 3,000 kinds of sativa, indica, and hybrid cannabis plants. Seedfinder (2021) currently lists 21,236 strains of cannabis. One of the most comprehensive, printed publications to date on modern cannabis plant varieties, by S. T. Oner (2011–2014), is in six volumes. Three volumes are devoted to 300 sativa strains and three to 300 indica strains. But how accurate is this simple two-fold classification of cannabis?
The botanical classification of cannabis
Although the cannabis plant was described by several Greco-Roman authors, in more recent times, the botanical classification began in 1542 with the identification and image of Cannabis sativa in work on plants (De historia stirpum commentarii insignes) by the German physician and botanist Leonhart Fuchs (Russo 2007:1616). However, the name ‘Cannabis sativa’ was coined by Ermolao Barbaro between 1480 and 1490 but only published twenty-three years after he died (McPartland and Small 2020:82).
More than 200 years later, Carolus Linnaeus, the Swedish ‘father’ of modern botanical classification, also identified Cannabis sativa from specimens growing in Holland and Sweden (Stearn 1975:17) in his 1753 compendium Species Plantarum. The so-called ‘sativa’varieties which grew in Europe and Russia, which were farmed on a large scale in Europe, Russia, and North America between around 1600 and 1920, were psychoactively weak and generally known as ‘hemp.’
The classification of the cannabis into Cannabis sativa and Cannabis indica began with the Frenchman Jean-Baptiste Lamarck in his Encyclopédie méthodique, publishedin 1785 (Schultes and Hofmann 1980:88). Lamarck believed that the indica variety, known for its distinctive psychoactive properties, was the kind native to India and Persia.
Cannabis ruderalis, a small (two feet high), dark green, weedy variety found primarily in parts of southern Russia, Siberia, Eastern Europe, and Central Asia, was subsequently described by the Russian biologist D. E. Janichevsky in 1924 (Koren et al. 2020:3), making a tripartite classification of the naturally growing cannabis plant (Clarke and Merlin 2013:316ff.).
It was only in the 1960s that botanists began to be persuaded that cannabis may not be a monotypic plant but, rather, polytypic (Schultes et al. 1975:24). However, more recently, some scientists have argued that Cannabis indica should—again—be classified as a subspecies of Cannabis sativa. The genetic differences between the two varieties are so slight (Lynch et al. 2017:358; McPartland 2018:209; McPartland and Small 2020).
One observation that adds support for Cannabis ruderalis being a strain historically distinct from either sativa or indica is the inherent capacity for ruderalis to auto-flower (McPartland 2018:211), a process not induced by photoperiod but by plant maturity. As neither sativas nor indicas auto-flower, ruderalis varieties are now being crossed with sativas and indicas to induce auto-flowering (Green 2013:xiv; Seedsman 2018). Cannabis ruderalis may be the ancestor of European hemp varieties or even the ancestor of all cannabis strains (Clarke and Merlin 2013:xvi; McPartland and Small 2020:358).
In the late-1970s, cannabis cultivators in North America and Europe began producing numerous hybrids of sativas and indicas derived from landraces from many different countries where cannabis grows.
Sativa strains from Central and South America, such as Colombia Gold, Panama Red, and Acapulco Gold, did not grow as well in the USA as they did in their original countries, which led to extensive hybridization with indica strains, particularly Hindu Kush indicas from Afghanistan and Pakistan (Thomas 2013a:xvii-xviii). Hybrid technology was also significantly developed in the Netherlands. Hybrid indica varieties became popular because they were easier to grow and the greater number of useful medical applications for indicas (see Backes 2017; Seedsman.com). However, although sativa strains waned in popularity in the 1990s, more recently, there has been a resurgence in interest in them (Thomas 2013b: xviii).
Diverse botanical classifications
Looking back at the complex history of cannabis taxonomy (Clarke 1981:157–161; Clarke and Merlin 2015:314–317; Koren et al. 2020; McPartland 2018), it can be seen that numerous, diverse classifications of the cannabis plant have been proposed.
The botanical classification of cannabis remains one of the most controversial among plant species. The main complication for taxonomy is that all wild cannabis populations can interbreed (Koren et al. 2020:2) and have done so over several millennia. Also, cultivated cannabis plants often become wild and may revert to previous characteristics. In addition, historical, selective breeding by humans for either fibre, seed, or resin, which may have begun around 5,000 BCE with the advent of farming, and also the transportation of seeds, not only by migrant populations but also by birds and in horses’ hooves, has led to multiple sub-species of cannabis.
All of this has further complicated our understanding of different kinds of cannabis plant species. Although there is some consensus on the geographical origins of cannabis types, McPartland (2018:210) comments that interbreeding and hybridization of cannabis have made the current sativa/indica classification almost meaningless.
Not only have hybrids further complicated the modern classification of plant varieties, but also, since the early 1970s, foreign landraces and hybrids have been introduced into cannabis-growing regions in Asia, Africa, and the Caribbean (McPartland and Small 2020:85), mainly to increase THC content, making identification of ‘local’ varieties even more problematic. Nowadays, it is impossible to guess the biochemical or THC content of a cannabis plant-based simply on its height, branching, or leaf morphology (Piomelli and Russo 2016:45; Tipperat et al. 2014:48). McPartland (2018:219) notes that AK 47 won ‘Best Sativa’ in the 1999 Cannabis Cup and ‘Best Indica’ four years later.
The main differences between strains as understood nowadays
The general, modern consensus of three main cannabis species (sativa, indica, and ruderalis), which is reflected in popular literature and known to cannabis connoisseurs, is now being challenged by some scientists. The conventional classification is as follows.
Cannabis sativa strains have thinner leaves, are taller, spindlier, have less dense branch formations, and are generally reputed to have a proportionally higher THC component. Sativa buds tend to be smaller than those of indicas.
Cannabis indica strains have broader leaves, are shorter, bushier, and are reputed to be higher in CBDs, with proportionally less THCs. Indicas usually have more chlorophyll than sativas, grow more quickly and flower more rapidly than sativas, as indicas generally grow and flower in a shorter time (around 105 days) than sativas (around 133 days) (Casano et al. 2011:116). Indicas also tend to have more cannabinoids than sativas.
Cannabis ruderalis, the third, ‘weedy’/‘roadside’ variety, has a low THC and CBD content.
THCs and CBDs
THCs provide the stimulating ‘high’ of cannabis, while CBDs are believed to have a generally non-psychoactive, sedating effect. Indica strains, often containing proportionally more CBDs, usually have a greater effect on the body, causing inactivity (sometimes referred to as ‘couchlock’) and affecting appetite. At the same time, sativas stimulate the mind and provide the ‘psychedelic’ component. For this reason, the majority of cannabis medicines are derived from indicas, owing to the higher CBD content.
However, Russo (Piomelli and Russo 2016:46) comments that this is mistaken, as the sedative effects of cannabis are not primarily due to CBDs, but rather to myrcene, a terpene which is present in high levels in most common cannabis strains and highest in Cannabis ruderalis (Casano et al. 2011:117; Lynch et al. 2017:359; McPartland and Small 2020:359–360). The terpenes humulene and linalool also produce sedative effects. Interestingly, the highest levels of linalool have been found in broad-leaf drug types (BLDT), more than in narrow-leaf drug types (NLDT) or hemp (see below) (Lynch et al. 2016:350).
Psychoactivity of sativa and indica strains
Even though many of the sativa varieties that are these days grown, imported, and consumed are quite obviously psychoactive, many with a high THC content, some scientists and scholars still maintain that all of the sativa varieties grown as ‘hemp’ in previous centuries in Europe and the USA for cloth, fibre and seed were not psychoactive at all. This is based on the notion that cannabis plants have just two main ancestors, sativa and indica, and that in the past, sativa strains grown as hemp were not psychoactive. However, recent studies have shown this inaccurate: cannabis varieties cannot be simply classified as a simple binary of non-psychoactive sativa/psychoactive indica (Hillig and Mahlberg 2004:972). There are no strict relationships between fibre characteristics and cannabinoid content (de Meijer 2016:90).
Some native sativa varieties may have a shallow THC content, but others may have a high THC content. Also, cannabinoid production results from genetic ancestry and daylight length, ambient temperature, nutrient level, and the amount of ultra-violet light that the plant receives (Clarke 1981:160; Hillig and Mahlberg 2004:967; Singh et al. 2021:495).
Currently, cannabis plants—of whatever variety—in the former USSR and Europe with less than 0.2% THC can be legally classified and grown as ‘non-drug hemp, while the limit is 0.3% in Canada, 0.35% in New Zealand (Doh et al. 2019:5), and 0.5% (or up to 1%, depending on climate and environmental conditions) in Queensland, Australia (Tipparat et al. 2014:47).
Genetic profiling and chemotaxonomy
Although the cannabis plant has been of great importance to agricultural and social history, it is presently the only multi-billion-dollar crop without a sequence-based genetic linkage or physical genome map (Lynch et al., 2016:351). So far, no profiling of Cannabis ruderalis has been undertaken; this would greatly improve understanding of genetic variation in the genus (Vergara et al., 2017:4–7).
Recent chemotaxonomic and genetic studies have refined understanding of the diversification of cannabis. Based on the chemotaxonomic analysis of 157 cannabis varieties worldwide, Hillig (2005:173–176) endorses the basic, historical, binary classification of sativa/indica and considers ruderalis as a possible third original species. He proposes two areas in Asia as the original sources of two main gene pools of cannabis: sativa from Central Asia, around Uzbekistan, and indica from further south, in and around Afghanistan. However, systematic studies have also established that cannabis was native to Europe around 1.8–1.2 million years ago, a long time before human agency or cultivation (McPartland 2018:203; McPartland et al. 2018:643), indicating that Europe was another region, besides Central Asia, where cannabis was indigenous.
Chemical composition of cannabis types
Scientists currently researching cannabis varieties are variously proposing different schemes of classification, not necessarily based on the simple, visual sativa/indica and relative CBD/THC content classification, but based on degrees of psychoactivity.
Rather than classifying types of cannabis based on THC or CBD content, it has also been proposed that the monoterpene content of cannabis plants can be a reliable indicator of whether the plant has either a sativa or indica ancestry (Casano et al. 2011:118). As noted above, some terpenoids are pharmacologically active and may synergize the effects of the cannabinoids (Hillig 2004:879).
Recent categorization of cannabis types
From a genetic study of eighty-one psychoactive (‘marijuana’) and forty-three non-psychoactive ‘hemp’ cannabis samples, Sawler et al. (2015:2–4) conclude that although sativa/indica classification is in partial agreement with the strain-specific ancestry of the plant, implying distinguishable pools of genetic ancestry, there are some interesting, additional findings. Firstly, the difference between ‘hemp’ and ‘marijuana’ varieties is not limited to genes involved in THC production. Secondly, ‘hemp’ strains are more likely to have an indica than a sativa ancestry. These findings are contrary to the commonly held view that only sativa strains were used for hemp production.
In another study (Jin et al., 2021:486), twenty-one mature varieties of both sativa and indica cannabis plants were analysed. It was found that higher CBD content correlated with more leaflets, narrower and longer central leaflets, and more primary and secondary serrations in the higher leaves. On the other hand, plants with more THC correlated with taller plants, larger stems, a deeper green colour, more nodes, wider central leaflets, and a higher yield of inflorescences. These results also challenge current conventional ideas about the basic differences between modern sativa and indica varieties.
Recent research has led to several alternative taxonomic proposals. Vergara et al. (2017:7) suggest a three-fold division of cannabis types: hemp, narrow-leaf drug type (NLDT), and broad-leaf drug type (BLDT). This is because there is not much genetic difference between NLDT and BLDT, but more difference with hemp. McPartland and Small (2020:355) concur with this three-fold distinction but add that there may be a distinct south-east Asian NLDT variety. Lynch et al. (2017:358) also observe that Asian ‘hemp’ varieties are, in fact, more similar to Asian drug varieties than to narrow-leaf European kinds of ‘hemp.’
In another comprehensive study, from the analysis of 147 varieties of cannabis, Hillig (2004:881; 2005:176) proposes three species (sativa, indica, and possibly ruderalis) and seven probable taxa (see also Clarke and Merlin 2013:xvi):
C. indica hemp biotype Hemp landraces of southern and eastern Asia
C. indica feral biotype Wild or feral populations of southern and Eastern Asia
C. indica narrow-leaf drug biotype Strains from the Indian subcontinent, Africa, and other
C. indica wide-leaf drug biotype Strains from Afghanistan and Pakistan
C. sativa hemp biotype Hemp landraces from Europe, Asia Minor, and Central
C. sativa feral biotype Naturalized populations of eastern Europe
C. ruderalis Ruderal populations of central Asia
More recently, McPartland and Small (2020:93–101) have also challenged the ‘traditional’ sativa/indica classification and propose, instead, a four-fold classification of historical cannabis varieties: (1) South Asian domesticate; (2) South Asian wild-type; (3) Central Asian domesticate; and (4) Central Asian wild-type.
Cannabis sativa vs Cannabis indica conclusion
Recent chemotaxonomic and genetic studies indicate that although the modern, general classification of cannabis into sativa and indica types may be partially accurate as an indicator of a cannabis plant’s genetic ancestry, this scheme has little use when it comes to determining the chemical constituents and likely effect of a particular plant, whether that be a hybrid or a native landrace. This is because of the widespread, multiple varieties of the cannabis plant that have historically resulted from natural interbreeding and human selection for specific properties, such as fibre, seed, or psychoactivity. As observed in the discussion above, there is still considerable disagreement amongst experts on how the numerous varieties of cannabis plants should be accurately classified.
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