Green teas are made from the unoxidized buds and younger leaves of the tea plant. Unlike other types of teas, green teas are heated immediately to prevent oxidation. This preserves the freshness of these teas. The processing of green tea demands the utmost care because any bruising of the leaf will immediately induce oxidation.
The taste and quality of a green tea relies heavily on its harvesting date — early harvests produce younger leaves, which are sweeter and more prized than the mature leaves picked from later harvests. However, as with other teas, processing also has a great effect on the flavor of green teas. For example, roasted green teas tend to be nuttier than steamed green teas, which tend to be grassier. The general flavor profiles of green tea are vegetal, nutty, astringent and even grassy; the finish of green tea is almost always clean.