Animal bedding, rope, insulation, building materials, textiles, and paper are just a few of the common uses of hemp stalks. Hemp (Cannabis sativa), also called industrial hemp, a plant of the Cannabaceae family that is cultivated for its viber fiber or its edible seeds.
Hemp issometimes confused with cannabis plants that serve as a source of the drug marijuana and hashish, a pharmacological preparation. Although all three products, hemp, marijuana and hashish, contain tetrahydrocannabinol (THC), a compound that produces psychoactive effects on humans, the variety of cannabis that is cultivated for hemp contains only small amounts of THC compared to that cultivated for the production of marijuana or hashish.
The hemp plant is a robust, aromatic and erect annual herb. The thin, cane-shaped stems are hollow except at the tip and base. The leaves are composite with a palmate shape and the flowers are small and greenish yellow. The flowers that produce seeds form elongated spike-shaped clusters that grow on pistillate or female plants.
Pollen-producing flowers form clusters with many branches on staminate or male plants. The cultivation of hemp for fiber was recorded in China as early as 2800 BC. C. and was practiced in the Mediterranean countries of Europe at the beginning of the Christian era, spreading to the rest of Europe during the Middle Ages.
It was planted in Chile in the 16th century and a century later in North America. Hemp is grown in temperate areas as an annual seed-based plant and can reach a height of up to 5 meters (16 feet). Crops grow best in sandy loam soil with good drainage and require an average monthly rainfall of at least 65 mm (2.5 inches) during the growing season. Crops grown for fiber are planted densely and produce plants that are 2 to 3 meters (6 to 10 feet) tall with almost no ramifications.
Plants that are grown for oilseeds are planted further apart and are shorter and have many branches. In fiber production, maximum yield and quality are obtained by harvesting shortly after the plants reach maturity, as indicated by full flowering and the pollen freely released by male plants. Although sometimes plucked by hand, the plants are usually cut about 1 inch (2.5 cm) from the ground. The fibers are obtained by subjecting the stems to a series of operations that include shredding, drying and shredding them, and to an agitation process that completes the separation of the woody part, releasing the long and fairly straight fiber or line.
Fiber yarns, generally larger than 1.8 meters (5.8 feet), are made up of individual cylindrical cells with an irregular surface. The fiber, which is longer and less flexible than linen, is usually yellowish, greenish or dark brown or gray in color and, because it does not easily discolor into sufficiently light tones, it is rarely dyed. It is strong and durable and is used as a string, for example. Some specially processed types of hemp have a whitish color and an attractive sheen, and are used to make linen-like fabrics for garments.
Hemp textiles can be used to make shoes. Hemp fiber is used to make recyclable and biodegradable bioplastics, depending on the formulation. The novel “hemp concrete”, a composite material of hemp and a lime binder, can be used in a similar way to traditional concrete in applications that do not withstand loads. Hemp can also be used as an alternative to wood pulp in some cases; it is frequently used in paper manufacturing and is a sustainable alternative to fiberglass insulation in buildings.
Although only the hemp plant produces true hemp, other plant fibers are referred to as “hemp”. These include Indian hemp (Apocynum cannabinum), Mauritian hemp (Furcraea foetida) and sunn hemp (Crotalaria juncea). Shelled hemp seeds, sometimes called hemp hearts, are sold as a health food and can be eaten raw; they are usually sprinkled on salads or mixed with fruit smoothies. The oil obtained from hemp seed can be used to make paints, varnishes, soaps and edible oil with a low smoke point.