Pu'er or pu-erh is a variety of fermented tea traditionally produced in Yunnan Province, China. Pu-erh tea is made from the leaves of the Yunnan tea plant Camellia sinensis var. assamica,which is a specific variety of tea plant that is native to Yunnan Province. It differs from Yunnan tea (Dianhong) in that pu'er tea goes through a complex fermentation process. In the context of traditional Chinese tea production terminology, fermentation refers to microbial fermentation (called 'wet piling'), and is typically applied after the tea leaves have been sufficiently dried and rolled. As the tea undergoes controlled microbial fermentation, it also continues to oxidize, which is also controlled, until the desired flavors are reached. This process produces tea known as hēichá (黑茶), literally "black tea", though the term is commonly translated to English as "dark tea" to distinguish it from the English-language "black tea" (紅茶 hóngchá, lit. "red tea" in Chinese), which it is not.
Most teas, although described as fermented, are actually oxidised by enzymes present in the tea plant. Pu'er is instead fermented microbially by molds, bacteria and yeasts present on the harvested leaves of the tea plant, and thus is truly fermented.
