Industrial hemp is the common name for fibre and grain cultivars of Cannabis sativa L. (C. sativa). Hemp is an herbaceous annual which has been domestically cultivated for its bast and hurd fibres, whole and pressed seed, essential leaf oils and epidermal resins (Small and Marcus 2002; Booth 2003; per. comm. J. Lupien 2008).

Hemp Bast Fibre

In 1753, Carolus Linnaeus, a Swedish botanist, formally keyed the Cannabis plant as Cannabis sativa L. (Schultes 1970; Booth 2003). To date, a debate has existed over whether or not the Cannabis plant is monotypic, having one species with different varieties, or polytypic, having distinct subspecies (Booth 2003). In 1924, the Russian botanist D.E. Vanischewsky studied feral wild Cannabis in the Volga River system of western Siberia and central Asia (Booth 2003). Vanischewsky supported the polytypic argument, claiming that in addition to Cannabis sativa and Cannabis indica, there was a third distinct wild species: Cannabis ruderalis (Vavilov 1926; SLDP 2007).

Hemp Hurd

Based on an extensive Cannabis cultivar review, Small and Conquist (1976) concluded that C. sativa was monotypic, possessing two distinct subspecies. These subspecies were classified by the percentage of active cannabinoids (a category of molecules found only in Cannabis) (Clarke 1981), mainly delta⁹-tetrahydrocannabinol (Δ⁹-THC or THC), the main psychoactive compound in Cannabis (Clarke 1981), present in the dry weight of the upper part of the female inflorescence. Small and Conquist (1976) keyed the two subspecies: C. sativa subspecies sativa, with less than 0.3% THC (3000 parts per million) and C. sativa subspecies indica (Lam), with more than 0.3% THC. Within the subspecies sativa are variety sativa and spontanea, and within the subspecies indica are variety indica and kafiristanica (De Meijer 1994). Hilling and Mahlberg’s (2004) examined the cannabinoid variations of 157 Cannabis accessions, in which their research findings supported the two-species theory, thus chemotaxonomically authenticating the C. indica sub-species biotype. Others have further categorized Cannabis based on geographical race and morphological and physiological characteristics (Bòsca and Karus 1998; McPartland et al. 2000). Nonetheless, the classification of Cannabis has been internationally controversial.

Hemp Seedcake Produced from Cold Pressing Hemp Grain
Seedcake is milled into a range of hemp powders.

Taxonomically, the genus Cannabis belongs to the Order Rosales; Family Cannabinaceae; Genus Cannabis (Bócsa and Karus 1998; Small and Marcus 2002). It was formally classified as belonging to the Urticaeae (Nettle) Family (Dewey 1901) and at one time was classified as part of the Moraceae (Mulberry) Family (Dempsey 1975; Frank 2005). Even though today, a general consensus has been reached regarding the taxonomic classification, the origin of Cannabis is truly unknown, due mainly to the Cannabis plants’ ability to adapt to its environment, no matter the origin of its seed (McPartland et al. 2000).

Resources:

1. Small, E. and Marcus, D. 2002. Hemp: A New Crop with New Uses for North America. Trends in new crops and uses. 284-326.
2. Booth, M. 2003. Cannabis a History. Doubleday, Transworld Publishers, London. 354.
3. Schultes, R. E. 1970. Random thoughts and queries on botany of Cannabis. In The Botany & Chemistry of Cannabis.  Eds. Joyce, C.R.B. and Curry, S.H. J & A Churchill,London 1-10
4. Vavilov, N.I. 1926. Centers of origin of cultivated plants. In, N.I.Vavilov Origin and geography of cultivated plants. Ed. V.F. Dorofeyv.Cambridge:CambridgeUniversityPress.  477-485.
5. SLDP. Schaffer Library of Drug Policy: Marijuana — The first twelve thousand years. February 20, 2007.
6. Small., E. and Cronquist, A. 1976. E. 1 A practical and natural taxonomy for Cannabis. Taxon. 25:405-435.
7. Clarke, R.C.1981. Marijuana Botany. Ronin Publishing, Inc., Berkeley, CA.
8. de Meijer, E. P. M. 1994. Diversity in Cannabis. Ph.D. diss. Wageningen Agricultural University, Wageningen, TheNetherlands.
9. Hillig, K.W. and Mahlberg, P.G. 2004. A chemotaxonomic analysis of cannabinoid variation in Cannabis (Cannabaceae). Am. J. Bot. 91(6):966-975.
10. Bócsa,I.and Karus, M. 1998. The cultivation of hemp – Botany, Varieties, Cultivation and Harvesting. Hemptech, Sebastopol, CA. 23.
11. McPartland, J.M., Clarke, R.C. and Watson, D.P. 2000. Hemp diseases and pests: management and biological control. CABI publishing.Cambridge,MA. 251pp
12. Dewey, L.H. 1901. The Hemp Industry in the United States. The Hemp Plant. Yearbook of the Department of Agriculture. 541-554
13. Dempsey J.M. 1975. “Hemp” in Fiber Crops. University of Florida Press, Gainesville, FL. 46-89.
14. Franck, R.R. ed. 2005. Bast and other plant fibers. The Textile Institute.Woodhead Publishing Limited,Cambridge,England. 177-206.