All tea, green, black and oolong, originates from the same small tea shrub. This is known as the Camellia Sinensis, however a combination of environment, coupled with human intervention has led to the creation of some distinct varieties of tea plants. These are known as cultivars and differ in taste, structure and tolerance to specific conditions in the same way that wine producers have created the shiraz, merlot and cabernet strain of grape vines. So its quite possible to have one tea bush and to use some leaves to produce green tea, some leaves to produce oolong tea and some leaves to produce black tea.
The real difference between green, oolong and black teas is the processes that the leaves go through following the harvest. This in particular relates to the level of decomposition that the leaves are able to undergo before being packed ready for consumption. So green tea leaves are picked and then quickly heated with steam or in an oven to stop the fermentation process. At the other end of the spectrum, those that want to obtain black tea will allow the leaves to oxidize or ferment completely before heating and drying them to stop the decomposition process.
The Taiwanese, due in part to their Chinese and Japanese expertize, have realised that an incredible range of flavours with associated health benefits can be obtained if the decomposition / oxidization process is carefully controlled somewhere between 0% (green tea) and 100 % (black tea) to create a special type of tea called Oolong tea. Oolong tea is therefore any tea that is semi oxidized (partially fermented). The degree of fermentation is generally anywhere between 5%, which produces a very light tea to 95% which produces an intense red tea, often referred to as red oolong, ruby red, red jade or black oolong tea.
Taiwanese tea is reputed to be the best in the world with some oolong teas costing the equivalent of a car for a 150 gram packet. For this reason the Taiwanese government is keen to maintain the quality, reputation and authenticity of its teas. This task is seconded to the Taiwanese Tea Research Station (TRES). TRES is a team of experts and scientists that are dedicated to producing the highest quality of tea in the most environmentally advantageous manner. Their research and subsequent education has led to many of islands small holders to adopt organic and natural methods. TRES also experiments with the creation of new types of tea, famously the number 18 or cocoa black oolong tea that it helped to create in the 1980’s.