Decaffeination this trait could be bred into other coffee plants by crossing them with "C. charrieriana", or an equivalent effect could be achieved by knocking out the gene for caffeine synthase in normal coffee plants. Tea may also be decaffeinated, usually by using processes analogous to the direct method or the CO process, as described above. The process of oxidizing tea leaves to create black tea ("red" in Chinese tea culture) or oolong tea leaves from green leaves does not affect the amount of caffeine in the tea, though tea-plant subspecies (i.e., "Camellia sinensis sinensis" vs. "Camellia sinensis assamica") may differ
Tea a year and prefer acidic soils. Many high-quality tea plants are cultivated at elevations of up to above sea level. Though at these heights the plants grow more slowly, they acquire a better flavour. Two principal varieties are used: "Camellia sinensis" var. "sinensis," which is used for most Chinese, Formosan and Japanese teas, and "C. sinensis" var. "assamica," used in Pu-erh and most Indian teas (but not Darjeeling). Within these botanical varieties, many strains and modern clonal varieties are known. Leaf size is the chief criterion for the classification of tea plants, with three primary classifications being, Assam type, characterised