Oolong refers to semi-oxidized tea. The oxidation process lends oolong tea an exceptionally smooth and rich flavor. Fujian oolongs are heavily oxidized so that the leaves are dark green or even an earthy brown. On the other hand, Taiwan oolongs are lightly oxidized so that the leaves hold on to their green color. Oolong teas encompass a wide swath of the taste spectrum. Some teas are infused with a sugarcane-sweet flavor, while others have heavier notes of caramel.