Description and Natural History of Hemp

[Picture of Female Hemp Plant] Cannabis sativa has many common names: hemp, marijuana, bhang, ganja, hashish, etc. It is an annual herb in the hemp family (Cannabaceae) which grows 3-10 feet tall and has hairy leaves divided into 5 to 7 serrated leaflets; the leaves are often sticky with resin. The plants are distinctly male or female (male and female flowers are produced by separate plants) and they flower from June to October.

Hemp is one of the oldest and one of the most all-round useful economic plants. Its fibers have been used to make high-quality paper, rope, twine, and cloth (the original Levi's jeans were made from hemp); its seeds have been eaten as a high-protein grain, turned into a tofu-like nondairy cheese substitute, and pressed to make oil for paints and varnishes; its leaves and flowers have been eaten or smoked as a medicine or intoxicant.


It was originally native to the Caucasus region of far eastern Europe, northern India, and Persia (Iran) but it is now cultivated in warm-to-temperate regions all over the world. Archaeologists have found 10,000-year-old pot shards imprinted with hemp fibers. The Chinese documented its medicinal values over 4,000 years ago; they used the seeds to treat pain, fever, ulcers, nausea, and many other ills. The Arabs started using the plant at least by the mid-1200s, and they in turn introduced it into Africa in the 1500s and 1600s. Europe discovered hemp incrementally, starting with Marco Polo's return from his journey to the East in 1297; later, Crusaders brought back stories and seeds from the Middle East. It was introduced to South America in 1545 by the Spaniards, and the British started growing hemp in Jamaica and the New England colonies in the early 1800s.
It was legal in the U.S. until the 1920s and 1930s, when several factors led to its criminalization: legitimate concern over addiction, an anti-marijuana crusade begun to justify the existence of the new federal Narcotics Bureau, and possibly racism (hemp smoking was a popular theme in African-American and Latino jazz music of the era). Varieties of hemp that mostly lack tetrahydrocannabinols (its medicinal/intoxicating compounds) are still cultivated for fiber in the U.S., and in many places the plant has escaped the fields and grows as a common weed.


Aside from its well-known intoxicating properties, the tetrahydrocannabinols (THCs) in hemp have documented medicinal value. Its leaves and sap have been universally used as a painkiller and sedative, and its roots were used by ancient herbalists to make salves for burns and other wounds. In 1965, scientists isolated THC and later discovered that the compound can lower pressure in the eyes of glaucoma patients and has thus far been an excellent drug for glaucoma treatment. They also discovered THC dilates bronchial tubes and can therefore benefit asthma sufferers. Later, they discovered that THC has antispasmodic properties that could possibly benefit people with epilepsy. And finally, THC has proven to give relief to patients undergoing chemotherapy by helping to alleviate the nausea they often suffer, and many AIDS and cancer patients have found it stimulates their appetite, thus combatting the wasting associated with their illnesses.


Because of this, the federal government decided to allow doctors to prescribe THC in the form of pills or cigarettes (some reports indicate that the federally-approved cigarettes contain much less THC than street-grade joints). A federal study in 1972 and a study by the National Academy of Sciences in 1981 both recommended that marijuana use be decriminalized. The latter study found that although immediate use causes mental impairment and heavy, long-term use causes physical problems, they could determine no long-term ill effects for occasional, light users and concluded that on the whole marijuana was no more dangerous than alcohol and tobacco. Side effects of THC intoxication include impaired short-term memory, impaired ability to complete complicated tasks, a sense of time slowing down, hunger, and changes in sensory perceptions. A very high acute dose may cause anxiety or panic attacks; it may also cause seizures in persons with epilepsy. Negative effects of long-term heavy (daily) use for smokers include emphysema and lung cancer. There is also the possibility for psychological (potentially physical) addiction for both smokers and those who ingest the drug.


Though hemp is far less toxic than any of the other plants used in cancer treatment, it still has potentially serious side effects and is illegal to use or possess except with a doctor's prescription, so self-medication is not advised.


For more information, visit:


 Dobelis, Inge N., ed. 1989. Magic and Medicine of Plants. Pleasantville, NY, Reader's Digest Books.

 1995 Physician's Desk Reference ©. Montvale, NJ, Medical Economics Data Production Company.

 Simpson, Beryl Brintnall and Molly Conner-Ogorzaly. 1986. Economic Botany: Plants in Our World. New York, NY, McGraw-Hill Publishing Co.


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 This page was last updated 11/5/97.