Where green tea began
Green tea is the oldest way of processing tea leaf, and every other category grew out of it.
The oldest physical evidence is leaf found in a Han dynasty tomb, dated to roughly 141 BCE.
The oldest written record of tea being bought is a contract from 59 BCE that names a market at Wuyang.
Neither source says how the leaf was processed, and the honest answer is that nobody knows.
What is documented is that fixation, called sha qing（杀青）, is the step that makes a tea green.
Heat is applied early to stop the leaf oxidising, and everything else in the category follows from that.
Lu Yu’s Classic of Tea, written between 760 and 762 CE, describes steaming leaf and pressing it into cakes.
Cake tea stayed the standard form for centuries, and the tea it describes is not what anyone drinks now.
Loose leaf became the norm after an imperial decree in 1391 stopped the making of tribute cakes.
Pan firing then replaced steaming across most of China, and the two methods have been diverging ever since.
So the history of green tea is largely the history of one decision, which is how to apply the heat.
Steaming and pan firing remain the two families, and they fall along regional lines.
China main regions
China grows green tea in nearly every province that grows tea at all, and four regions dominate the trade.
Zhejiang is the first, and Longjing（龙井）from the hills above West Lake is what the province is known for.
Its flat leaf and nutty sweetness come from being pan fired by hand in a hot wok.
Jiangsu is the second, and Biluochun（碧螺春）is picked tiny and rolled into a snail shape.
The gardens sit on islands in Taihu lake among fruit trees, and the tea picks up a faint floral note from them.
Anhui is the third, and it produces several distinct teas rather than one famous one.
Huangshan Maofeng is a bud tea from high ground, Taiping Houkui is a long flat leaf, and Lu’an Guapian is made from leaf alone.
Sichuan is the fourth, and Mengding Ganlu from a mountain above the Chengdu plain is its oldest named tea.
Henan’s Xinyang Maojian grows further north than most and picks late, which gives it a tight savoury cup.
Hunan, Jiangxi, Guizhou and Shandong all produce green tea, and most of it is drunk inside China.
Enshi Yulu in Hubei is one of the few Chinese green teas still steamed rather than pan fired.
That puts it closer in flavour to a Japanese tea than to anything else made in the country.
Japan and beyond
Japan took the steaming method and never gave it up, which is the one thing worth knowing about it.
Leaf is steamed within hours of picking, and that fixes a green colour and a vegetal sweetness.
Uji near Kyoto is the historic centre, and shaded growing and matcha were both developed there.
Shizuoka is the largest producing area, and much of the country’s everyday sencha comes from it.
Yame in Fukuoka and Kirishima in Kagoshima are the other two names that come up regularly.
Gyokuro is shaded for about 20 days before picking, which changes the cup more than any other step in green tea.
Matcha is made from the same shaded leaf, dried and stone ground, and Nishio in Aichi is its main source.
Korea makes small volumes of green tea on the southern coast, mostly pan fired and delicate.
Vietnam produces a great deal of green tea, and most of it is strong, cheap and bought for blending.
India makes green tea in Darjeeling and Assam, generally in a Chinese style rather than a Japanese one.
Taiwan makes green tea too, although the island is far better known for oolong.
Kenya, Sri Lanka and Indonesia produce green tea for export as a commodity rather than as a region.
What the region gives the cup
The first thing a region gives you is the fixation method, and it matters more than the soil does.
Steamed tea tastes sweet, grassy and slightly marine, and pan fired tea tastes nuttier and rounder.
Drinkers who dislike one family often like the other, so trying both is the fastest way to find out.
Cultivar comes second, and it decides the leaf size and how much bud ends up in the pick.
Small leaf bushes suit the tiny rolled shapes, and larger leaf suits the flat pressed ones.
Picking date comes third, and in China the harvest before Qingming（清明）carries a large premium.
That early pick is more tender and less bitter, and the price gap is wider than the taste gap.
Elevation acts through the picking date rather than through flavour, much as it does in white tea.
Water is the fourth thing a region contributes, and it is the one that cannot be exported.
Brew 3 grams in a 150 ml vessel at about 80 °C and steep for 2 minutes, keeping the water well off the boil.
Compare a steamed tea against a pan fired one first, then compare regions within either family.
That order teaches you more about what you like than any list of famous names.