One Plant

Every true tea - green, white, yellow, oolong, black, pu-erh - is made from the leaves of Camellia sinensis. Not different plants, not different species in any meaningful sense for a drinker. The same shrub.

What differs is what is done to the leaf after picking, and the single most important variable in that processing is oxidation.

When a tea leaf is picked, enzymes inside it begin reacting with oxygen, exactly as a cut apple browns. This changes the colour from green to copper to dark brown, and it changes the flavour from vegetal and fresh towards malty, fruity, and sweet. Tea processing is fundamentally the business of deciding how far to let that reaction go and then stopping it, usually with heat.

Once you know that, the categories stop being a list to memorise.

Green Tea: Oxidation Stopped Immediately

The leaves are heated within hours of picking - steamed in the Japanese tradition, pan-fired in the Chinese - which deactivates the enzymes and locks the leaf in its fresh state.

The two heating methods produce genuinely different drinks. Steamed Japanese greens such as sencha and gyokuro taste marine, grassy, and savoury, with a deep green liquor. Pan-fired Chinese greens such as longjing taste nuttier, sweeter, and toastier, with a pale yellow-green liquor.

Green tea has the most delicate compounds and the least tolerance for hot water, and it is the type most often ruined at home.

White Tea: Almost No Processing At All

Picked and dried. Minimal handling, and consequently a small amount of oxidation happens anyway.

Silver Needle is buds only; White Peony includes leaves and is more robust. The flavour is subtle, hay-like, and softly sweet, which makes white tea easy to under-appreciate and difficult to make taste bad.

White tea takes far more leaf and far longer than people expect. The usual disappointment - that it tastes of nothing - comes from brewing it like green tea.

Yellow Tea: Green, Plus a Slow Smother

Rare, mostly Chinese, made like a green tea with an added slow damp-resting step that removes the grassy edge and leaves something rounder and mellower. Worth trying if you find it; not worth hunting.

Oolong: Partially Oxidised, and the Broadest Category

Oolong is anything oxidised between roughly ten and eighty percent, which makes it less a category than a continent.

Green oolongs - lightly oxidised, often rolled into tight balls, such as Tieguanyin or the Taiwanese high mountain teas - are floral, creamy, and buttery.

Dark oolongs - heavily oxidised and often roasted, such as the Wuyi rock teas or Dan Cong - are toasty, stone-fruited, mineral, and closer to a black tea.

Oolongs are also the teas that reward repeated short steepings most dramatically. A good rolled oolong will give six or more infusions, each noticeably different, which is one of the more genuinely enjoyable things in tea.

Black Tea: Fully Oxidised

Called red tea in China, after the colour of the liquor rather than the leaf.

The leaves are withered, rolled or crushed to break the cell walls, left to oxidise fully, then fired. The result is malty, brisk, and robust, and it is the only category that reliably survives milk.

Within it: Assam malty and strong, Darjeeling lighter and muscatel, Ceylon brisk and citrus, Yunnan sweet and peppery, Keemun wine-like and slightly smoky.

Most supermarket teabags are CTC - crush, tear, curl - which is machine-processed into granules. It extracts fast and hard, which is exactly what you want for a strong builder’s tea with milk, and it is not a defect so much as a different product.

Dark Tea and Pu-erh: Fermented by Microbes

The one category where something other than oxidation is happening: actual microbial fermentation, over months or years.

Sheng (raw) pu-erh is made like a green tea, pressed into cakes, and left to age slowly for years or decades. Young sheng is astringent and bitter; aged sheng becomes deep and complex.

Shou (ripe) pu-erh is a 1970s process that accelerates this with a controlled damp pile, producing an earthy, smooth, dark tea in months.

Pu-erh is the one tea genuinely improved by age, and the one where storage conditions are part of the product.

Herbals Are Not Tea

Chamomile, peppermint, rooibos, hibiscus, ginger, fruit blends - none of these come from Camellia sinensis, and the accurate word is tisane or infusion.

Practically, this matters for two reasons: they contain no caffeine (except yerba mate and guayusa, which do), and they are almost all brewed with full boiling water for a long time, because there are no delicate tea compounds to scorch. Under-brewing a herbal is far more common than over-brewing one.

Rooibos is worth a mention as the closest herbal substitute for black tea: it takes milk, brews strong, and does not turn bitter.

Caffeine, Briefly

A common claim is that green tea has less caffeine than black. It is largely a myth. Caffeine content depends far more on the plant variety, the age of the leaf picked, how much leaf you use, and how hot and how long you brew than on the category. Bud-heavy teas such as gyokuro and Silver Needle can be very high in caffeine indeed.

If you want less caffeine, use less leaf, brew cooler and shorter, or drink a herbal.