Buckthorn is a European shrub native to Asia and Europe that is now distributed throughout North America. It is also known as Black Dogwood because the wood was once used to produce fine charcoal. Before use in teas or tisanes, the bark must be aged for one year. While buckthorn bark has a slightly bitter but not unpleasant taste, moderation is advised because it contains the phenolic compound emodin. *Because of buckthorn's powerful laxative action, it should not be used by people with chronic gastrointestinal problems, such as ulcers, colitis, or hemorrhoids. Pregnant women should not take buckthorn. Don't use buckthorn for more than two weeks at a time. If you use it too long, it causes lazy bowel syndrome — an inability to produce stool without chemical stimulation.*