Hemp (Cannabis sativa), also known as industrial hemp, is a plant in the Cannabaceae family that is grown for its bast fibre or edible seeds. Hemp is frequently confused with cannabis plants, which are used to produce the drug marijuana and the drug preparation hashish.
Although all three products—hemp, marijuana, and hashish—contain tetrahydrocannabinol (THC), a compound that causes psychoactive effects in humans, the variety of cannabis grown for hemp contains far less THC than that grown for marijuana or hashish.
Hemp is a robust, aromatic, erect annual herb. Except at the tip and base, the slender canelike stalks are hollow. The leaves are palmately compound, and the flowers are small and greenish yellow. Seed-producing flowers grow in long spikelike clusters on pistillate, or female, plants. On staminate, or male, plants, pollen-producing flowers form many-branched clusters.
Production and processing
Central Asia is where hemp originated. Hemp cultivation for fibre was documented in China as early as 2800 BCE and was practised in Mediterranean European countries early in the Christian era, spreading throughout the rest of Europe during the Middle Ages. It was first planted in Chile in the 1500s, and then in North America a century later.
Hemp is grown as an annual from seed in temperate zones and can reach heights of up to 5 metres (16 feet). Crops grow best in sandy loam with good drainage and require at least 65 mm (2.5 inches) of rainfall per month during the growing season. Plants grown for fibre are densely sown and grow to be 2–3 metres (6–10 feet) tall with almost no branching. Plants grown for oilseed are planted farther apart, shorter, and have more branches.
Maximum yield and quality are obtained in fibre production by harvesting plants as soon as they reach maturity, as indicated by full blossoms and freely shedding pollen on the male plants. Although plants are occasionally pulled up by hand, they are more often cut off about 2.5 cm (1 inch) above the ground.
The stalks are subjected to a series of operations, including retting, drying, and crushing, as well as a shaking process, which completes separation from the woody portion, releasing the long, fairly straight fibre, or line. Individual cylindrical cells with an irregular surface make up the fibre strands, which are typically longer than 1.8 metres (5.8 feet).
Products and applications
The fibre, which is longer and less flexible than flax, is usually yellowish, greenish, or a dark brown or grey, and is rarely dyed because it is difficult to bleach to sufficiently light shades. It is strong and long-lasting, and it is used for cordage, such as twine, yarn, rope, cable, and string, as well as artificial sponges and coarse fabrics like sacking (burlap) and canvas.
Some specially processed hemp has a whitish colour and an attractive lustre and is used to make fabric for clothing similar to linen. Shoes can be made from hemp textiles. Depending on the formulation, hemp fibre is used to make bioplastics that are recyclable and biodegradable.
The novel "hempcrete," a composite material made of hemp and a lime binder, can be used in non-load-bearing applications in the same way as traditional concrete. In some cases, hemp can be used instead of wood pulp; it is commonly used in papermaking and is a sustainable alternative to fibreglass insulation in buildings.
The edible seeds contain about 30% oil and are high in protein, fibre, and magnesium. Shelled hemp seeds, also known as hemp hearts, are sold as a health food and can be consumed raw; they are frequently sprinkled on salads or blended with fruit smoothies.
In drinks and recipes, hemp seed milk is used in place of dairy milk. Hemp seed oil can be used to make paints, varnishes, soaps, and edible oil with a low smoke point. Historically, the seed's main commercial application has been as caged-bird feed.
Other types of hemp
Although only the hemp plant produces true hemp, a variety of other plant fibres are referred to as "hemp." Indian hemp (Apocynum cannabinum), Mauritius hemp (Furcraea foetida), and sunn hemp are examples (Crotalaria juncea).
Cannabinoids are any of more than 80 known chemical compounds found in all parts of the cannabis plant (specifically the species Cannabis indica and Cannabis sativa), with a high concentration in the female flower heads. They are responsible for the physical and psychological effects that result from the consumption of marijuana (the dried leaves and flowers of the plant) and its derivatives.
Cannabinoids have numerous effects on humans. Tetrahydrocannabinol is the primary psychoactive chemical found in cannabis (THC). It produces mild euphoria and hallucinations, which is the "high" sought by many marijuana users. Several mammalian species, including humans, have a receptor for a substance produced naturally by the body that resembles THC and is thus susceptible to THC's effects.
Cannabidiol (CBD) is another important cannabinoid. It has a sedative and relaxing effect on the body. Cannabinoids are typically inhaled by smoking marijuana. Cannabis can also be made into a concentrated resin (hashish), vaporised, or consumed (alone or in food).
Despite the fact that marijuana is one of the world's most popular recreational drugs and is still illegal in many countries, medical marijuana and other cannabis derivatives have gained acceptance in some circles. Cannabinoids may stimulate appetite and alleviate nausea in chemotherapy patients.
Marijuana has also been used to treat medical conditions like chronic pain and glaucoma. Cannabinoids can be delivered for medical purposes by smoking or ingesting specially grown strains of marijuana in states where medical marijuana is legal, or by distillation in states where marijuana is illegal. Many employers and professional bodies, such as the World Anti-Doping Agency (WADA), which sets drug testing standards for the Olympics, prohibit marijuana consumption and test for the presence of cannabinoids. Cannabinoids are fat soluble, and modern tests can detect them long after they have been consumed.
Common side effects of cannabinoids include difficulty concentrating, impaired motor skills, dry mouth, depression or apathy, panic attacks, paranoia, and anxiety. According to research, users do not develop a strong physical dependence on cannabinoids, and there are no significant physical withdrawal symptoms when they are stopped.
However, psychological dependence can occur. Frequent users have reported headaches, nausea, irritability, and depression shortly after quitting.
Sunn (Crotalaria juncea), also known as sann hemp or Indian hemp, is an annual plant in the Fabaceae family that produces a bast fibre. Sunn is most likely indigenous to the Indian subcontinent, where it has been grown since prehistoric times.
Sunn is not a true hemp plant. The fibre is used to make cordage, fishing nets, sacking fabrics, canvas, and rug yarns, as well as paper products such as cigarette and tissue papers. Many tropical countries grow the plant as a green manure crop that is ploughed under to fertilise soil.
Sunn is grown from seed and is sown densely to limit lateral leaf growth. It grows best in loamy, well-drained soil, but it is adaptable to poor soils and relatively arid climates and is frequently grown in rotation with rice, corn (maize), and cotton. The plants grow to a height of 2.5 to 3 metres (8 to 10 feet). The leaves are bright green in colour, pointed in shape, and range in length from 5 to 7.5 cm (2 to 3 inches).
The small yellow flowers appear in spikelike clusters at the angle formed by the leafstalk and the plant stem (leaf axil). When seedpods form on fibre crops, they are cut or pulled out; when green manure crops flower, they are ploughed under. A retting operation is followed by stripping, washing, and drying to obtain fibres.
Sunn fibre is lustrous and comes in whitish, grey, or yellow hues. The 1 to 1.5 metre (3.3 to 5 foot) long fibre strands are made up of individual fibre cells that are cylindrical in shape and have striated surface markings. Sunn fibre is nearly as strong as hemp and lasts longer than jute. It gains strength when wet and is moderately resistant to mildew.
Tetrahydrocannabinol (THC) is an active constituent of marijuana and hashish that was isolated from the Indian hemp plant (Cannabis sativa) and synthesised in 1965.