More than just an exoticism, Puer tea has seen a dramatic rise in the Western market. Despite the hype and fluctuating prices, Puer still remains some of the most expensive tea in China.

So, what exactly is Puer tea?

Puer, or 普洱 (pǔ ěr), is a type of fermented tea from China’s Southwestern Yunnan Province. It comes in two styles: Sheng (or raw) Puer, which is allowed to naturally ferment over time by aging, and Shu (or cooked) Puer, which utilizes a wet-piling process to speed up fermentation.

To be considered a Puer, the tea leaves must be grown in Yunnan and must be from descendants of Camellia sinensis var. assamica, known colloquially as Da Ye Zhong (大叶种) or large leaf type. Both Sheng Puer and Shu Puer begin life as Mao Cha (毛茶), literally ‘coarse tea’ or ‘unfinished tea’. Mao Cha, the raw material for Puer, is made by pan-firing fresh leaves, rolling them, and finally drying them in the sun. At this point, the Mao Cha can be made into Shu Puer or Sheng Puer; the only difference is how the leaves are fermented.

Fermentation in tea production refers to the breakdown of substances by bacteria, yeasts or other microorganisms and has traditionally been a source of confusion in Western tea culture. For too long, it was propagated that black tea was fermented, but this process is actually enzymatic oxidation. Puer is, in fact, fermented.

Even though the name Puer is sometimes used categorically in the West to mean “all fermented tea”, Puer is only one style of many fermented teas in China, which are generally known as hei cha (黑茶), or dark tea. I typically see tea books and classification charts claiming Puer as the “6th Tea Category”, but this leaves out many other styles, such as hei cha and several Japanese teas. Puer is firmly nestled in a broader “Fermented tea” category.

Here’s more on tea classification.

puer tuocha sticky rice teaBoth Sheng and Shu Puer begin with the same processing steps, then undergo a hou fajiao (后发酵), or fermentation process. Sheng Puer doesn’t fall neatly under the ‘hei cha’ moniker, mostly due to the lack of a wo dui (渥堆) step, or wet piling, that Shu Puer undergoes to quickly ferment it. Sheng’s fermentation happens during aging, which can last a few months to many decades. At what point during aging it technically becomes “fermented” is really a scientific question without a clear answer. How much microbial fermentation has to occur versus enzymatic oxidation in order for it to be a “fermented” tea? It comes down to the intent to make an aged tea, and the assumption that aging for any amount of time will involve some fermentation.

After wet-piling, in the case of Shu Puer, or before aging, in the case of Sheng, Puer is compressed into a variety of different shapes for aging, presentation, and dosing. These shapes can range from a flat cake (Bing Cha – 饼茶), to a flat square (Fang Cha – 方茶), to a small bowl (Tuo Cha -沱茶). It can even be packed into oranges.