One leaf, three drinks: how tea diverged

Nearly all tea comes from one species, Camellia sinensis, in two main varieties. The enormous differences between teas come from cultivar, growing conditions and — above all — processing.

Oxidation is the main variable

When a tea leaf is picked and bruised, enzymes in the leaf react with oxygen. The leaf darkens, and the flavour compounds change substantially: fresh, grassy notes give way to fruit, malt and, at the far end, dark and woody characteristics.

This process is frequently called fermentation in the tea trade, which is a misnomer — no microorganisms are involved in most of it. It is enzymatic oxidation, chemically the same kind of process that browns a cut apple.

The processor's central decision is when to stop it, which is done with heat: firing in a pan or a drying chamber, or steaming. Heat denatures the enzymes and the leaf stays where it is.

The categories

Green tea. Oxidation stopped almost immediately after picking. Chinese practice generally uses pan firing, which contributes a toasted, nutty note; Japanese practice generally uses steaming, which preserves a greener, more marine character. The two taste distinctly different and the difference comes largely from that single choice.

White tea. Minimally processed — withered and dried, with very little handling. Slight oxidation occurs naturally. Typically made from young buds and leaves.

Yellow tea. Rare. Similar to green with an additional slow, gentle smothering step that mellows the flavour.

Oolong. Partially oxidised, anywhere across a broad range, with repeated bruising of the leaf edges and rolling. The most technically involved category, with the widest variation — lightly oxidised oolongs are floral and close to green tea; heavily oxidised and roasted ones approach black tea.

Black tea, called red tea in Chinese usage. Fully oxidised. The category that dominates world trade, largely because it survives long transport and storage better than green tea.

Dark tea, including pu-erh. The genuine exception, where microbial fermentation is involved. Leaves are processed and then aged, sometimes for years, with microbial activity transforming them. Aged pu-erh is a category with its own connoisseurship and its own speculation.

The other processing decisions

Withering reduces moisture and makes leaves pliable enough to handle without shattering.

Rolling or shaping breaks cell walls, controlling how fast oxidation proceeds and how the leaf releases flavour in water. It also determines the visual form — twisted, rolled into pellets, pressed into cakes, or cut small.

Roasting, in some traditions, applied after processing and sometimes repeatedly over years, adding depth and changing the character considerably.

Scenting, most famously with jasmine, where flowers are layered with the tea repeatedly so it absorbs the aroma.

The two production philosophies

Most of the world's tea is produced by a mechanised method that cuts leaves into small particles, which oxidise quickly and produce a strong, fast-brewing, consistent liquor. It is efficient, it suits tea bags, and it is what most tea drinkers encounter.

The alternative keeps leaves whole through a longer, more manual process. It produces more nuanced tea and far less of it per hour of labour, and it is what nearly all traditional and specialty tea is.

Neither is a fraud. They are answers to different questions.

How it is drunk

The preparation traditions differ as much as the tea.

The small-pot method used across parts of China and Taiwan uses a high leaf-to-water ratio and very short steeps, repeated many times, with the tea changing across the session. Japanese practice varies enormously by tea type, with some green teas brewed at surprisingly low temperatures. The British method of a large pot, a long steep and milk suits a strong black tea and would ruin a delicate green one.

Tea with milk, salt and butter is standard across the Himalaya and Central Asia, where it functions as a substantial food rather than a beverage. Sweetened, spiced preparations across South Asia are again a different drink from the leaf's origin.

Each of these evolved around a locally available tea and locally available additions, and each is coherent on its own terms.

The trade that reshaped things

Tea's history is inseparable from the economics around it: the tea trade's role in colonial commerce, the establishment of plantations in South Asia and East Africa to break existing supply monopolies, and the labour systems used to run them.

Those origins remain visible in the industry. A significant share of the world's tea is still produced on large estates by workers whose conditions have been the subject of sustained criticism, and the price paid at auction for bulk tea has been low enough for long enough that improvement is difficult.

The specialty market pays considerably more for small-producer tea, which has created viable alternatives for some growers. It remains a small share of a very large industry.