Pu-erh teas come from Yunnan province and improve with age. Some are still drinkable at age 50. They come in green, black, white and brick tea. These are teas with medicinal qualities, highly prized by the connoisseur. Tea leaves are withered, then, still slightly moist, they're heaped into piles where a bacterium creates a reaction. The leaves are then dried loose or compressed into tea bricks or cakes.
The peoples of the Yunnan-Tibet border have drunk pu-erh since the Tang dynasty, according to a Song dynasty scientific reference. The troops of Kublai Khan, "pacifying" the southwest after the 13th century Mongol conquest, are said to have introduced pu-erh to the rest of China for its medicinal value. Bricks of pu-erh tea constituted the first medium of monetary exchange used by nomads beyond the Great Wall of China, recorded in Chinese records as early as A.D. 476.
The aroma and flavor are earthy, and pu-erh is often blended with other teas. It is said to help lower blood pressure levels and increase metabolism. All the teas in this category are cooked to hasten the aging process, and have been aged five years or more.