Hemp (from Old English hænep) is mostly used as a name for low tetrahydrocannabinol (THC) strains of the plant Cannabis sativa, of fiber and/or oilseed varieties. In modern times, hemp has been used for industrial purposes including paper, textiles, biodegradable plastics, construction, health food and fuel with modest commercial success. Since 2007, commercial success of hemp food products has grown considerably.
Hemp is one of the faster growing biomasses known, producing up to 25 tonnes of dry matter per hectare per year. A normal average yield in large scale modern agriculture is about 2.5–3.5 t/ac (air dry stem yields of dry, retted stalks per acre at 12% moisture). Approximately, one tonne of bast fiber and 2–3 tonnes of core material can be decorticated from 3–4 tonnes of good quality, dry retted straw.
For a crop, hemp is very environmentally friendly as it requires few pesticides, when not grown industrially and no herbicides. Results indicate that high yield of hemp may require high total nutrient levels (field plus fertilizer nutrients) similar to a high yielding wheat crop.
Hemp is one of the earliest domesticated plants known.
Cannabis sativa L. subsp. sativa var. sativa is the variety grown for industrial use, while C. sativa subsp. indica generally has poor fiber quality and is primarily used for production of recreational and medicinal drugs. The major difference between the two types of plants is the appearance and the amount of Δ9-tetrahydrocannabinol (THC) secreted in a resinous mixture by epidermal hairs called glandular trichomes, although they can also be distinguished genetically. Oilseed and fiber varieties of Cannabis approved for industrial hemp production produce only minute amounts of this psychoactive drug, not enough for any physical or psychological effects. Typically, hemp contains below 0.3% THC, while cultivars of Cannabis grown for marijuana can contain anywhere from 2% to over 20%.
The world leading producer of hemp is China with smaller production in Europe, Chile and North Korea. While more hemp is exported to the United States than to any other country, the United States Government does not consistently distinguish between marijuana and the non-psychoactive Cannabis used for industrial and commercial purposes.