The Chinese tea known for microbial fermentation, aging, and compressed forms is pu-erh tea.
Pu-erh is traditionally produced in Yunnan from the broad-leaf tea plant Camellia sinensis var. assamica. Unlike black tea, which is primarily enzymatically oxidized, pu-erh undergoes microbial fermentation involving molds, bacteria, and yeasts. This creates the earthy, woody, mushroom-like, or sometimes camphor-like flavors associated with aged examples.
There are two principal styles. Raw, or sheng, pu-erh is allowed to mature gradually over years, while ripe, or shou, pu-erh undergoes an accelerated wet-piling process. The modern wet-piling method was developed in 1973 by the Kunming and Menghai tea factories to imitate the character of naturally aged tea; ripe tea can be ready in months rather than decades.
Pu-erh is often pressed into cakes, bricks, bowls, or nest-shaped tuos for storage and transport. Compression is not merely decorative: dense forms protect the tea during aging and reflect older tea-trade practices. A frequent mistake is treating all dark-colored tea as black tea. In Chinese classification, pu-erh is generally a fermented dark tea, while English “black tea” usually refers to a different, fully oxidized category.