Cannabis plant. Hemp (Cannabis sativa), the source of the narcotic drug marijuana. The plant is native to central Asia. It is cultivated for its seed oil and fibres, as well as for use as a narcotic. It is a fast-growing annual. In good conditions it can grow to over five metres tall with numerous side branches. The drug is produced in minute resin glands on the plant surface, including the leaves, but is most concentrated in female flowers. Marijuana is made from the dried leaves and flowers. It is usually smoked. The concentrated resin is termed hashish. Cultivating cannabis to make drugs is banned in many countries.