Oolong Tea comes from the Camellia family and is native to China. When the British went to India, they imported tea from China and eventually developed their own strain of tea. Thus, all tea comes from the same family of plants and all teas are very closely related. The only difference between teas made from the Camellia plant is the degree of oxidation of the tea leaves. Oxidation is also known as fermention. However, no microorganisms are involved in this process. Instead, fermentation refers to the the browning of the leaves as they are bruised and exposed to air. The process if very similar to the browning of an apple when exposed to air.
Oolong tea has long been made in China through a special process involving exposure to the air. What this does is spur chemical reactions between substances within tea. This process also gives the different types of tea their distinct flavor and color. oolong tea belongs between green tea and black tea in classification. Because it is neither full oxidized, nor left in its natural state, much skill is required to pick out a properly prepared batch of oolong tea. Oolong is truly a craft on par with winemaking.
To oxidize tea, manufactures harvest the tea leaves and hand roll the leaves to bruise them, exposing them to air for a period of time that requires artisan precision and experience. The leaves are then roasted in a pan coated with tea oil in order to lock in the flavor. Then, the leaves are dried and stored in a cool place for distribution.
The grade of oolong depends on the age of the tea plants and the portion of the plant from which the tea leaves are picked. The younger the leaves used for tea, the higher the grade.