There are over 400 different varieties of hemp recorded by the Vavilov Institute in St. Petersburg, Russia, that are used for the production of both fiber and seed.
The official botanical designation for true hemp is as follows:
- division – Magnoliophyta (flowering plants or angiosperms)
- class – Magnoliopsida
- order – Urticales
- family – Cannabinaceae
- genus – Cannabis
- species – sativa
Although its closest relative is the hops plant, because of morphological and anatomical similarities, hemp was once classified in the mulberry family (Moroaceae). Later, it was classified in the nettle family (Urticaceae).
Many modern botanists classify the genus Cannabis as having only one species, sativa, with varieties consisting of indica (Indian hemp – with a subvariation called Gigantea or giant hemp), ruderalis (wild hemp), and vulgaris (cultivated hemp). However, most food and fiber comes from C. sativa.
Hemp seed is technically an achene, that is, a small, indehiscent fruit that is dry and usually containing an oily germ. Sunflower seeds are another example of an achene. The hard hulls of achenes usually have no significant nutritional value and are often removed before consumption. Hemp seed hulls, however, are among the easiest of achenes to chew and digest.
Hemp botanists and researchers Sisov and Serebrjakova separate the genus Cannabis into two species, sativa and indica and only one of the subspecies, culta. This has economic significance
They deem the subspecies, spontanea (wild hemp), as not being economically important. According to their classification, cultivated hemp cannot be systematically categorized but rather subdivided into geographical races or ecological form groups.
It is important to note that these geographical varieties have considerable morphological and physiological differences. Nevertheless, they do share a common trait: all have the same number of chromosomes (2n=20) and readily interbreed with one another.
According to Sisov and Serebrjakova, the following geographical race and ecological form groups include the following:
- borealis (Northern hemp) – This group belongs to the geographical races from Russia and Finland. They are grown north of 60° north latitude.
- medioruthenica (Central Russian hemp) – This group is cultivated on the majority of the total hemp acreage, generally between 50° and 60° north latitude, predominantly in Russia, the Ukraine, and Poland, but also in Scandinavia and in northern Germany.
- australis (Southern or Mediterranean hemp) – This group is a variety found throughout central, southeastern, and southern Europe. The Hungarian, Italian, Spanish, Turkish, and southern Russian geographical race of hemp belong to this group, as do the most valuable varieties.
- asiatica (Asian hemp) – This group contains varieties cultivated in China, Japan, Thailand, and Korea.
- Northern hemp (C. borealis) has a very short stalk and rarely exceeds a maximum height of 1.5 m (5 feet). This group is similar to Central Russian hemp, but matures much sooner. The world’s earliest maturing varieties of hemp belong to this group, but their global economic significance is meager. Important to the north, they are the only cultivable fiber and oil plants.
- Central Russian hemp (C. medioruthenica) was developed in the Russian plains and Poland as well as in northern Germany prior to 1980. This is mainly because of the influence of prevailing climatic conditions between the 50th and 60th north latitude. That is, it has a short vegetation period, long days, high precipation and so on. This group occupies the largest total acreage. Important characteristics include: 90-110 days to seed maturation, grows 4-9 feet in height, has a lightly branching stalk, leaf size compares to southern or Asiatic geographical races with an average of 5-9 leaflets. Fiber is mediocre but produces large amounts of seeds. All cultivated varieties in the European region, in central Asiatic sections of Russia, Poland, and northern Germany, belong to this group.
- Southern or Mediterranean hemp (C. australis) is important to the economy of the north. It is cultivated in Europe below 50° N latitude since the seeds do not ripen any farther north. It is cultivated in southern, southeastern, and central Europe (Romania, Hungary, the former Yugoslavia, and Bulgaria). It is also grown in southern Russia (around Krasnodar) as well as in southern Ukraine. Most varieties from Turkey also belong in this group. The northern boundary for seed production coincides with the boundary for wine-growing regions. However, fiber hemp from this geographical race can be grown considerably farther north in the regions 50° to 60° N latitude (Russia, Ukraine, and Poland), requiring 130-150 days to seed maturity. This geographical race has the longest stalks measuring 8-15 feet, which tends to branch out if the plant is free-standing. The leaves are large with the number of leaflets ranging from nine to eleven. These plants produce high stalk yields with many fibers, but the seed yield is much lower than central Russian varieties. Southern geographical races have the typical characteristics of a cultivated plant, producing high quality fiber with a large yield compared to their acreage. The monoecious varieties of hemp, including the French varieties, are transitional types of the southern and central Russian groups. The early-maturing monoecious varieties are more closely related to the latter type, while the late-maturing varieties are more closely associated with the previously cited type.
- Asiatic hemp (C. asiatica) develops smaller stalks (8-10 feet) and tends to branch out more than the others and has numerous short stalk segments. The leaves are large with bright pastel-green colouring. The number of leaflets is usually between nine and thirteen. Individual varieties have relatively large differences to their vegetation period, which averages 150-170 days; but there are a number of varieties whose seeds do not mature under central European conditions. Although they have no economic value in Europe, they can be used as hybrids for breeding.
- Wild hemp (C. spontanea), according to Sisov and Serebrjakova’s classification system, is a subspecies found mainly in central Asia and in the Volga and Ural regions of Russia. It can also be found in Turkey, Romania, Bulgaria, and Hungary but does not grow wild in countries west of Hungary. The plants are short with many branches and produces small seeds. Since wild hemp flowers irregularly, it is possible for it to flower simultaneously with cultivated hemp and since both interbreed easily. The result can be a biological degradation of the cultivated variety. Stalks are no taller than three feet with an usually large number of branches. Varieties with a longer stalk that occur spontaneously are not wild hemp but rather cultivated plants growing wild. Because they escaped cultivated areas, they could be considered weeds. These two ‘wild’ hemp types are neither systematically or morphologically identical.
Although Cannabis sativa is the original and true hemp, there are other similar fibrous plants that are using the generic word ‘hemp’. These include:
- Bastard hemp or false hemp (Datisca cannabina)
- Bowstring hemp (any of about 60 tropical African and Asian Agave-related plants of the genus Sansevieria, including African hemp [Sansevieria guineensis])
- Canada hemp (Apocynum cannabinum) – a species of dogbane
- Deccan hemp (Hibiscus cannabinus)
- Hemp agrimony (Eupatorium cannabinum)
- Hemp nettle (Galeopsis tetrahit)
- Indian hemp or, more commonly, jute (Corchorus capsularis – which is not to be confused with Cannabis indica, also known as Indian hemp)
- Manila hemp, or, more commonly, Abaca (Musa textilis)
- Mauritius hemp (Furcraea foetida)
- New Zealand hemp (Phormium tenax)
- Sisal hemp, or, more commonly, Henequen (Agave fourcroydes and A. sisalana)
- Sunn hemp (Erotolaria juncea)
- Sunnhemp (Crotalaria juncea)
- Water hemp (Acnida cannabina)