The hemp plant is a stout, aromatic, erect annual herb.
Hemp, (Cannabis sativa), also called industrial hemp, plant of the family Cannabaceae cultivated for its fibre (bast fibre) or its edible seeds. Hemp is sometimes confused with the cannabis plants that serve as sources of the drug marijuana and the drug preparation hashish. Although all three products—hemp, marijuana, and hashish—contain tetrahydrocannabinol (THC), a compound that produces psychoactive effects in humans, the variety of cannabis cultivated for hemp has only small amounts of THC relative to that grown for the production of marijuana or hashish.
The hemp plant is a stout, aromatic, erect annual herb. The slender cane-like stalks are hollow except at the tip and base. The leaves are compound with palmate shape, and the flowers are small and greenish-yellow. Seed-producing flowers form elongate, spikelike clusters growing on the pistillate, or female, plants. Pollen-producing flowers form many-branched clusters on staminate, or male, plants.
Cultivation and processing
Hemp originated in Central Asia. Hemp cultivation for fibre was recorded in China as early as 2800 BCE and was practised in the Mediterranean countries of Europe early in the Christian era, spreading throughout the rest of Europe during the Middle Ages. It was planted in Chile in the 1500s and a century later in North America.
Hemp is grown in temperate zones as an annual cultivated from seed and can reach a height of up to 5 metres (16 feet). Crops grow best in sandy loam with good drainage and require average monthly rainfall of at least 65 mm (2.5 inches) throughout the growing season. Crops cultivated for fibre are densely sowed and produce plants averaging 2–3 metres (6–10 feet) tall with almost no branching. Plants grown for oilseed are planted farther apart and are shorter and many-branched. In fibre production, maximum yield and quality are obtained by harvesting soon after the plants reach maturity, indicated by the full blossoms and freely shedding pollen of the male plants. Although sometimes pulled up by hand, plants are more often cut off about 2.5 cm (1 inch) above the ground.