Black, Green, Oolong and White teas all come from the same plant, a warm-weather evergreen named Camellia sinensis . Differences among the four types of tea result from the various degrees of processing and the level of oxidization. Black tea is oxidized for up to 4 hours and Oolong teas are oxidized for 2-3 hours. As a result, the tea leaves undergo natural chemical reactions, which result in taste and color changes, and allow for distinguishing characteristics. Green & White teas are not oxidized after leaf harvesting, so they most closely resemble the look and chemical composition of the fresh tea leaf. Oolong tea is midway between Black and Green teas in strength and color.