Hemp (Cannabis sativa L.) is botanically closely related to hops. See hops. Unlike the hop, it is an annual plant growing from seed every year. Hemp is an extremely vigorous, fast-growing plant with a straight stem that can grow to be several meters tall. Its main use has been as a fiber crop, and hemp ropes were once commonly used on sailing ships. However, because of its resins, which can have a high content of the psychoactive chemical compound Δ9-tetrahydrocannabinol (THC), it is also used as a drug. The concentration of THC is higher in specific selected “marijuana” strains and/or when the hemp is grown in sunny and warm areas. Today hemp is widespread all over the world with partially or completely restricted cropping in most Western countries because of its narcotic potential.

Hemp may have been used in ancient times in beer brewing but very little evidence suggests that it was ever widely used for this purpose. In recent years hemp leaves have been used in Western countries as a substitute for aroma-hopping in a limited number of specialty beers. Other beers have used the seeds, usually lightly toasted before their addition to the kettle. Some have claimed that hemp seeds add a nutty flavor to beer, but many people have found the flavor unattractive. Because of legal restrictions, only materials from cultivars of hemp with a very low content of THC are allowed. The use of hemp in beers, therefore, only adds flavor and aroma and not narcotic effects. If legal, hemp can easily be grown for home use in brewing. That said, it seems fair to say that use of hemp products in commercial beers is more a matter of juvenile titillation than of flavor and aroma. After a brief splash in the 1990s, use of hemp in brewing has largely faded from the scene.

See also herbs.