Cannabis (/ˈkænəbɪs/)[2] is a genus of flowering plants in the family Cannabaceae. The number of species within the genus is disputed. Three species may be recognized: Cannabis sativa, Cannabis indica, and Cannabis ruderalis; C. ruderalis may be included within C. sativa; all three may be treated as subspecies of a single species, C. sativa;[1][3][4][5] or C. sativa may be accepted as a single undivided species.[6] The genus is widely accepted as being indigenous to and originating from Asia.[7][8][9]
The plant is also known as hemp, although this term is often used to refer only to varieties of Cannabis cultivated for non-drug use. Cannabis has long been used for hemp fibre, hemp seeds and their oils, hemp leaves for use as vegetables and as juice, medicinal purposes, and as a recreational drug. Industrial hemp products are made from cannabis plants selected to produce an abundance of fiber. To satisfy the UN Narcotics Convention, some cannabis strains have been bred to produce minimal levels of tetrahydrocannabinol (THC), the principal psychoactive constituent. Some strains have been selectively bred to produce a maximum of THC (a cannabinoid), the strength of which is enhanced by curing the fruits. Various compounds, including hashish and hash oil, are extracted from the plant.[10]
In the US, "industrial hemp" is classified by the federal government as cannabis containing no more than 0.3% THC by dry weight. This classification was established in the 2018 Farm Bill and was refined to include hemp-sourced extracts, cannabinoids, and derivatives in the definition of hemp.[11]
Globally, in 2013, 60,400 kilograms of cannabis were produced legally.[12] In 2014 there were an estimated 182.5 million cannabis users (3.8% of the population aged 15–64).[13] This percentage did not change significantly between 1998 and 2014.[13]
Cannabis is an annual, dioecious, flowering herb. The leaves are palmately compound or digitate, with serrate leaflets.[14] The first pair of leaves usually have a single leaflet, the number gradually increasing up to a maximum of about thirteen leaflets per leaf (usually seven or nine), depending on variety and growing conditions. At the top of a flowering plant, this number again diminishes to a single leaflet per leaf. The lower leaf pairs usually occur in an opposite leaf arrangement and the upper leaf pairs in an alternate arrangement on the main stem of a mature plant.
The leaves have a peculiar and diagnostic venation pattern that enables persons poorly familiar with the plant to distinguish a cannabis leaf from unrelated species that have confusingly similar leaves (see illustration). As is common in serrated leaves, each serration has a central vein extending to its tip. However, the serration vein originates from lower down the central vein of the leaflet, typically opposite to the position of, not the first notch down, but the next notch. This means that on its way from the midrib of the leaflet to the point of the serration, the vein serving the tip of the serration passes close by the intervening notch. Sometimes the vein will actually pass tangent to the notch, but often it will pass by at a small distance,and when that happens a spur vein (occasionally a pair of such spur veins) branches off and joins the leaf margin at the deepest point of the notch. This venation pattern varies slightly among varieties, but in general it enables one to tellCannabis leaves from superficially similar leaves without difficulty and without special equipment. Tiny samples of Cannabis plants also can be identified with precision by microscopic examination of leaf cells and similar features, but that requires special expertise and equipment.[15]