To confess, when I was growing up, all "tea" was "black tea" to me. Boring. And as far as I knew, it grew in tea bags that hung from Lipton trees. When green tea had its renaissance in the 90’s as some form of exotic “cure-all”, I began to take interest (and enjoy it thoroughly). But when I learned black and green tea come from the same mysterious source (a plant otherwise known as camellia sinensis), I realized I had been fooled.
The defining feature of black tea, allowing the leaves to fully oxidize, is not as simple as it sounds. There are innumerable factors that go into the process, beginning with geographic location. Local terroir and the particular tea cultivar planted in that region will have a huge impact on the outcome of that tea before the leaves have even been plucked.
Local traditions and history may be the biggest factor. China, where black tea originated, has its own unique regional styles. But if the tea growing region was initiated by the former British Empire (India, Sri Lanka, Africa), this will have its own particular impact on the methods used. In Taiwan, their modern black teas are often being produced by the same farmers who have been making oolong tea for decades.
Even when the regions are inside the same political border, the outcomes can be wildly different. The Darjeeling and Assam regions of India are not geographically far apart, but produce teas that are nothing alike. Part of this is because Darjeeling uses the small-leaf Chinese tea plant, camellia sinensis-sinensis, smuggled out of China by the British spy Robert Fortune. This sub-species prefers high elevations and cooler temperatures. Assam uses their own indigenous plant, camellia sinensis-assamica, whose large leafs produce thick, lush teas and prefer the tropical climate of the Assam valley.
My original (and ignorant) assumption was that black tea was somehow boring and homogenous. I couldn’t have been more wrong. The variety is staggering. A well made first flush Darjeeling tea from India and a first grade Keemun from China are so different that it’s hard to recognize both of them as black teas. But that is why it is so fascinating.