Most of the Western World banned the cultivation of Cannabis sativa in the early 20th century because biotypes high in ∆9-tetrahydrocannabinol (THC, the principal intoxicant cannabinoid) are the source of marijuana. Nevertheless, since 1990, dozens of countries have authorized the licensed growth and processing of “industrial hemp” (cultivars with quite low levels of THC). Canada has concentrated on hemp oilseed production, and very recently, Europe changed its emphasis from fiber to oilseed. The USA, historically a major hemp producer, appears on the verge of reintroducing industrial hemp production. This 10-part presentation provides updates on various agricultural, scientific, social, and political considerations that impact the commercial hemp industry in the United States and Canada. The most promising scenario for the hemp industry in North America is a continuing focus on oilseed production, as well as cannabidiol (CBD), the principal non-intoxicant cannabinoid considered by many to have substantial medical potential, and currently in great demand as a pharmaceutical. Future success of the industrial hemp industry in North America is heavily dependent on the breeding of more productive oilseed cultivars, the continued development of consumer goods, reasonable but not overly restrictive regulations, and discouragement of overproduction associated with unrealistic enthusiasm. Changing attitudes have generated an unprecedented demand for the cannabis plant and its products, resulting in urgent needs for new legislative, regulatory, and business frameworks, as well as scientific, technological, and agricultural research.
Cannabis sativa L. is usually the only species of Cannabis recognized (and so is often referred to simply as Cannabis in this paper). This species has an extremely long association with humans. It is believed to have been a “camp follower”  during the nomadic, pre-agriculture stages of human development, thriving near ancient encampments associated with open areas, well-manured soils, and nearby streams, conditions providing the ideal habitat for the plant. Cannabis is one of the most ancient domesticated crops, cultivated for millennia. In the temperate world, as “hemp”, it was cultivated virtually exclusively as a bast (stem) fiber source, and the biotypes grown were so low in ∆9-tetrahydrocannabinol (THC), the principal intoxicating constituent of cannabis plants, that they could not be used as inebriants . By contrast, in southern Asia, C. sativa biotypes were selected that were very high in THC for use as spiritual and recreational drugs. Although only high-THC strains are employed for marijuana, concern over the growing use of the plant for drugs led to most of the Western World banning the cultivation of all forms of C. sativa in the early 20th century. By that time, competitive crops (cotton and other tropical fiber plants) had become much more important. Nevertheless, hemp production persisted in some countries, particularly China, where much of the world’s hemp for fiber is grown today.
Cannabis contains genetically different biotypes of both industrial (non-intoxicant) hemp and marijuana . “Hemp” or “industrial hemp” will be used interchangeably hereafter to refer to non-intoxicating C. sativa. Industrial hemp is sometimes referred to as “true hemp” to distinguish it from numerous other unrelated plant species that include “hemp” in their common names. Classification of Cannabis as either marijuana or industrial hemp is typically based on a threshold concentration of THC. Although a level of 1% THC is considered a minimum value to elicit an intoxicating effect, current laws in Canada and several other jurisdictions use 0.3% THC as the arbitrary threshold point at which cannabinoid content is used to distinguish strains of hemp from marijuana (a criterion first established by Small and Cronquist ). Cultivars of hemp must have less than the threshold THC concentration to be grown under license in Western countries permitting hemp cultivation. The European Union originally used a threshold value of 0.8%, later reducing it to 0.3%, and subsequently lowered to 0.2% THC. The reduction of the EU THC threshold to 0.2% was ostensibly done in the interests of safety, although 0.3% is widely accepted as sufficient. Excessive reduction of the criterion, which favors recent French cultivars over other sources, has the undesirable effect of eliminating some useful cultivars (e.g., FINOLA).
While “Cannabis” refers to a taxonomic genus, non-italicized, “cannabis” is a generic abstraction, widely used as a noun and adjective, and commonly (often loosely) used both for cannabis plants and/or any or all of the intoxicant preparations made from them. Note that throughout this review we use the term “intoxicant” in the standard dictionary sense of “inebriant”, not implying toxicity as do related words such as “intoxication”. However, in its most comprehensive sense “cannabis” also includes non-intoxicant, “industrial” preparations, which could be non-psychoactive medicinal drugs or other useful chemicals, fiber products (such as textiles, plastics and dozens of construction materials) and edible seed products .
Seed from industrial hemp is commonly referred to as “hempseed”, and the oilseed industry typically refers to the fixed vegetable oil extracted from hempseed as “hempseed oil”. Hempseed oil is distinguished from aromatic essential oils distilled from hemp inflorescences and/or foliage, and from “hash oil”, an extremely concentrated intoxicating more or less tarry preparation from high-THC strains. Although commonly referred to as a “seed”, the fruiting body of hemp is an achene, i.e., a fruit containing a seed. Hulling (i.e., removing the hull) from a hemp achene effectively removes the pericarp, leaving the true seed.
2. North American History in Brief
Hemp was cultivated in temperate Eurasia for millennia, and is believed to have been first brought to North America in 1606 . It was grown mainly for fiber in European settlements in Canada and the USA for several hundred years. The industry thrived in Kentucky, Missouri, and Illinois between 1840 and 1860, but was confined to Kentucky from the end of the civil war until around 1912 . In the 1920s, both Agriculture Canada and the US Department of Agriculture (USDA) were still conducting hemp fiber research. During World War I the hemp fiber industry briefly expanded to 12 USA states. There was also a small commercial hemp fiber industry in Canada in the 1920s and early 1930s, mostly in western provinces. In general during the 20th century hemp fiber became much less competitive for rope, apparel, and paper, and became obsolete for a variety of minor uses such as a waterproof packing .
In 1938, the Canadian Opium and Narcotics Act made cultivation of all Cannabis illegal. The US Marihuana Tax Act of 1938 did not technically make Cannabis cultivation illegal in the USA, but placed marijuana under control of the USA Treasury Department, requiring permission from the US Drug Enforcement Agency (USDEA) to grow Cannabis. A brief revival of hemp production in both Canada and the USA occurred during World War II, with 68,000 metric tons (MT) of hemp fiber produced on 59,000 hectares (ha) in the USA in 1943 (Figure 1) , but the 1938 legislation in both countries effectively eliminated hemp production in North America post World War II. One exception was the Rens Hemp Company of Wisconsin which was permitted by USDEA to produce hemp fiber until 1958 . In 1970, the US Congress repealed the 1937 Marijuana Tax Act and replaced it with the Comprehensive Drug Abuse Prevention and Control Act. Although the 1970 Act did create a distinction between marijuana and hemp, USDEA policy following the Act treated marijuana and hemp as the same plant.
Figure 1. Harvested area (ha) of hemp for fiber and for seed in the USA during the 1930’-s and 1940’-s. Source: .
In 1994, Canada started issuing licenses to allow research on industrial hemp. In 1998, new regulations included in the Canadian Controlled Drugs and Substances Act permitted commercial cultivation of hemp, under licensing and control of Health Canada. Section 7606 of the US Agricultural Act of 2014 authorized state departments of agriculture to permit pilot programs for industrial hemp research, although hemp remains classified as a Schedule 1 controlled substance under the USA Controlled Substances Act. Permission from both state departments of agriculture and USDEA are required to evaluate hemp in the USA under strictly controlled conditions.
Cannabis readily escapes from cultivation and establishes as a ruderal plant. After being introduced to North America as a field crop, it gradually spread from the primary areas of cultivation. Today, wild or ruderal Cannabis can be found in most states  and provinces , but remains more concentrated in southern Ontario and southern Quebec, and in the Midwest and Northeast USA, where hemp cultivation was focused in recent centuries. There have been concentrated efforts by law enforcement to eradicate wild hemp in North America, although it is not an aggressive weed and has virtually no capacity to produce intoxication. However, plants apparently growing wild in parks and wilderness areas are often marijuana strains being illegally cultivated.