Two countries share ways of making Oolong tea, also called Wu Long : Fujian province in Chine, its place of origin and the Island of Formosa (as il is still called in the world of tea) or Taiwan.
Wu Long means Black Dragon which symbolizes authority and nobility. These teas may also be called "blue-green" because they are half way between green tea and black tea. Or semi-fermented.
Futher explanation can be found under the sections "history of tea" and "the colours of tea".
Oolong teas of remarkable quality are the speciality of the island of Formosa, which produces Wu-Long : neither acidic, nor bitter, with a fresh fruity aroma, passing through woody notes with the fragrance of vanilla.