Dark tea (Chinese: 黑茶; pinyin: hēichá; literally "black tea") is a variety of post-fermented tea produced in China. Post-fermentation is a tea production style in which the tea leaves undergo a microbial fermentation process after they are dried and rolled. One of the most famous types of dark tea is pu-erh, produced in Yunnan Province.
The exact history on the emergence of dark tea is unclear, however there are several likely theories and legends.
One popular legend states that dark tea is thought to have been first produced accidentally on the Silk Road and Tea Road by tea caravans in the rainy season. When the tea became soaked by the falling rain, the tea transporters are said to have abandoned the tea in fear of contamination. The next year, nearby villages suffered from dysentery, and decided to drink the abandoned mildewed tea in desperation. The tea is said to have cured those suffering, and quickly became popular thereafter.
More historical accounts attribute the production of dark tea to the Ming Dynasty in the 15th and 16th centuries. Dark tea is said to have been first exchanged by tea merchants much earlier than the legends state, in areas on the borders of China and Tibet.
To produce dark tea, the base tea or maocha is rolled, moistened, and put in heaps to dry. This tea is then left to age and ferment for long periods of time until the tea leaves turn a dark black color. Some tea is packed into logs, and allowed to ferment outside in open sheds.
After the long fermenting period, the tea is packed in bamboo baskets, pressed into bricks, cakes, and other shapes, and even stuffed into bamboo.
Much of the dark tea packed into bricks and logs is sold along the borders of China, and is reserved for trade with Tibet. Other shapes, such as the round cakes, are sold elsewhere in China and around the world.
Varieties and producing areas
Dark tea is produced in many areas in China. It is often pressed into bricks (especially for trade with Tibet), logs, cakes, loose in baskets, and many others for aging.
Producing areas and varieties include:
- Yunnan: Pu-erh tea
- Guangxi: Liu Bao tea
- Anhui: Liu An basket tea (六安茶); 
- Sichuan: Sichuan Route tea (四川边茶)
- Hubei: Hubei Cha
- Xing'an and Guangxi: Liudong tea (六垌茶)
- Hunan: Fu Zhuan, Liang Cha
- Bamboo leaf logs
- Cakes, or "Bing Cha" (餅茶)
- Bricks, or "Zhuan Cha" (磚茶)
- Loose, in baskets
- Bird nests, or "Tuo Cha" (沱茶), usually specific to pu-erh
- Squares, or "Fang Cha" (方茶)
Aging and storage
As with many other post-fermented teas, the older the tea, the more sought-after it becomes. Dark tea is often aged in bamboo baskets, bamboo-leaf coverings, or in its original packaging.
Many varieties of dark tea are often purposely aged in humid environments to promote the growth of certain fungi, often called "Golden Flowers" or "Jin Hua" (金花) because of the bright yellow color.
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