"Wacholder" or juniper (Juniperus) is a plant genus that grows all over the northern hemisphere. There are dozens of species of juniper, from low, creeping plants to very tall trees. They bear a type of cone as they are related to pine trees, but the cone's scales are fused and fleshy, making it appear to be a berry.
Two main species of juniper grow wild in Europe. The "gemeiner Wacholder", or common juniper (Juniperus communis) is used as an herb in sauerkraut and meat and game dishes and to flavor gin, Genever, and other Wacholder liqueurs and schnaps as well as some beer.
The other species is Juniperus sabina, Savin juniper or "Sadebaum," which is native to mountains from Spain to Siberia. All parts of this plant are poisonous due to ethereal oils, especially "Sadebaumoel" or sabinol. Ingestion can lead to problems which include excessive bleeding of mucus membranes and the berries were used as an abortive herb in the Middle Ages. It has several ornamental varieties which are planted in gardens all over the world.
In addition to Savin juniper, Juniperus virginiana L. (red cedar) and Juniperus thurifera L. are also toxic.
Common juniper grows wild in North America too, as well as several other species, so before gathering your own berries, check to see if they are edible. You can check the USDA Plants Database, for instance, with the common or scientific name of the plant you want to know about.
Berries of common juniper are only toxic in large amounts, although people with kidney problems and pregnant women are advised against eating them. The ethereal oils are used in many herbal medicine applications in addition to their use in the kitchen. The amounts used in flavoring foods are far under the threshold for adverse reactions.
The flavor profile of the crushed berry is sharp, clear and resinous. They are most flavorful when fresh but are most often used dried as a spice. Juniper berries were used by Native Americans as an appetite suppressant during famines and some species of berries were actually slightly sweet and used as a food source. In Rome, they were used as a cheap substitute for expensive black pepper.
On Christmas, sprigs of juniper are tied to stall doors to keep out witches.
Gin is made when juniper berries and other plant materials are placed in grain alcohol which is then re-distilled.