The Two Varieties Behind Every Cup of Tea: Sinensis, Assamica, and the Surprising Truth About Japanese Black Tea

A variety, in the botanical sense, is a naturally occurring subdivision of a plant species. It is not a cultivar, which is a plant deliberately bred by humans. A variety emerged through natural selection over thousands of years in a specific environment. Two varieties of the same species share the same fundamental DNA but have diverged enough, in leaf size, growth habit, chemistry, and flavor, to be meaningfully distinct.

All true tea comes from a single species: Camellia sinensis. White tea, green tea, oolong, black tea, pu-erh, all of it comes from leaves of this one plant. The differences in color, flavor, and strength between tea styles are not the result of different plants. They are the result of different processing methods applied to the same leaf.¹

Within Camellia sinensis there are two varieties that matter for understanding tea.

Camellia sinensis var. sinensis, commonly called the Chinese variety, has small leaves, four to fifteen centimeters long, and grows as a compact shrub suited to cooler, higher-altitude environments. It produces tea that tends toward delicacy: fresh, floral, and lower in tannins. It is the variety behind almost all Chinese green tea, white tea, and virtually all traditional Japanese tea.²

Camellia sinensis var. assamica, commonly called the Assam or Indian variety, has dramatically larger leaves, up to thirty centimeters long, and grows into a tall tree suited to warm, humid, tropical conditions. It produces tea that tends toward boldness: full-bodied, higher in tannins, with the robust astringency that makes it well-suited to adding milk and sugar. It is the variety behind most of the world's commercial black tea, including Assam, Ceylon, and Kenyan tea.²

If you want to stop here, that is the essential picture. Sinensis: small leaf, delicate, cooler climates, most Japanese tea. Assamica: large leaf, bold, tropical climates, most international black tea.

If you want to understand why Japanese black tea is made from sinensis, why a Japanese cultivar developed for black tea ended up being celebrated as a green tea, and why variety matters less than most people assume, read on.

The story begins in southwestern China. The Yunnan province, particularly the Lancang River basin, is recognized by the International Tea Committee and the Food and Agriculture Organization of the United Nations as the origin of the tea plant.³ Ancient tea trees thousands of years old still grow there. Yunnan holds the richest genetic diversity of all tea populations on earth, and all other tea varieties trace back to this genetic source.³

Tea as a cultivated crop has a history of over 3,000 years in China.⁴ The earliest evidence of tea drinking dates to the Han dynasty, more than 2,100 years ago, when excavations at the Han Yangling Mausoleum in Shaanxi province revealed tea among the burial goods.⁴ From these origins in Yunnan and southern China, the tea plant spread across Asia, carried by trade, religion, and empire.

The two varieties we know today emerged from different branches of this spread, shaped by different climates, different soils, and millennia of human selection.

The basics section gave you the broad strokes. Here is what is worth understanding at a deeper level.

Camellia sinensis var. sinensis originated in southern China and spread across East Asia through trade and Buddhist cultural exchange. Its small leaf size is not incidental. It is an adaptation to the cooler, higher-altitude environments of southern China and Japan, where less intense sunlight means the plant produces a different chemical balance than its tropical counterpart: lower tannin content, higher relative amino acid production, and a more complex aromatic profile. This is why sinensis teas tend toward sweetness, umami, and floral complexity.²

Camellia sinensis var. assamica is adapted to warm, humid, low-altitude tropical conditions. Its larger leaves can sustain the metabolic cost of producing more polyphenols, including catechins and tannins, because energy from intense sunlight is abundant. This is the biological basis for its boldness and astringency.²

One important correction to the popular assumption: the name assamica reflects European naming conventions, not botanical origin. Assam tea was discovered by the British in the 1820s and 1830s when they found large-leaf tea trees growing wild in northeastern India. But genetic research has since shown that assamica actually originated in Yunnan, just like sinensis, and that the two varieties share a common ancestor.⁴ The British were not finding a new plant. They were finding a variety they had not previously encountered, growing far from where Europeans had learned to look.

Every tea plant growing in Japan today descends from a remarkably small number of original introductions. Tea was not native to Japan. It arrived from China, almost entirely as the sinensis variety, through a series of introductions carried by Buddhist monks between the sixth and twelfth centuries.⁵

The first documented reference to tea in Japan appears in records from the Nara period, in the eighth century. In 806, the monk Kukai returned from China and brought tea seeds with him. In 1191, the monk Eisai returned from China with seeds which he planted in Kyushu and gave to the monk Myoe, who established what became the Uji tea-growing tradition.⁶

These introductions were all sinensis. Small-leaf Chinese variety, adapted to the cooler mountain climates of China, which happened to suit Japan's tea-growing regions well. For over a thousand years, every tea plant in Japan was sinensis, and all of Japan's cultivation knowledge, processing methods, and flavor traditions developed around the characteristics of that one variety.

The consequence is genetic narrowness. China, as the origin of the tea plant, has thousands of years of natural genetic diversity across its tea populations. Japan received a handful of introductions over a few centuries. The genetic bottleneck is real, and it is why Japanese tea breeding, from Sugiyama Hikosaburo onward, has had to work harder to develop meaningful variation than Chinese breeders working with a richer natural palette.⁴

For most of Japan's tea history, assamica simply did not exist in the country. That changed in the postwar period, for a specific economic reason.

Japan desperately needed foreign exchange after World War II. Tea, alongside silk, was one of the few agricultural products Japan could realistically export. But the international black tea market was dominated by India, Ceylon, and China. Japan's green tea expertise was not directly transferable to the black tea styles that commanded export prices on the London market.

The government response was to bring assamica genetics into Japan deliberately. Assam seeds were obtained from India and successfully cultivated at the national research station in Kagoshima, which was well-suited to the warmer conditions assamica required.⁷ The goal was to develop Japanese black tea cultivars that could compete in international markets, combining assamica's robust oxidation characteristics with adaptations suited to Japanese growing conditions.

This was a turning point. For the first time, Japanese breeders had both varieties to work with. The crossbreeding programs that followed would eventually produce cultivars that are neither purely sinensis nor purely assamica, but hybrids carrying genetic contributions from both. And those hybrids would eventually change not just Japan's black tea but its green tea too.

Once assamica genetics were available in Japan, breeders began exploring what crossing the two varieties could achieve. The logic was straightforward: sinensis brought delicacy, amino acid richness, and adaptability to Japanese climates. Assamica brought robustness, higher polyphenol production, and the bold oxidation characteristics needed for black tea.

The results were not always what breeders expected. Some crosses produced cultivars better suited to black tea, as intended. Others produced cultivars with unexpected green tea qualities. And some produced chemical profiles that nobody had anticipated at all.

The crossbreeding work also confirmed something important about the two varieties: they are compatible enough to hybridize productively, but different enough that their offspring show genuinely novel characteristics rather than simply averaging the traits of the parents. The hybrid cultivars that emerged from this period represent a third category in Japanese tea genetics, neither purely sinensis nor purely assamica, but something new.

The most significant outcome of Japan's assamica crossbreeding program is Benifuuki. Developed in 1965 at the Ministry of Agriculture's Tea Research Station in Makurazaki, Kagoshima Prefecture, and registered in 1993 as Tea Norin No. 44, it is a cross between two parent plants: Benihomare, a Japanese cultivar of the assamica variety descended from seeds introduced from India in 1887 by tea pioneer Tada Motokichi, and MakuraCd86, a sinensis variety from Darjeeling.⁸

The story of MakuraCd86 is worth a brief aside. The seeds came to Japan through an unexpected channel: Maki Yuko, the mountaineer who participated in the second Manaslu expedition and later led the first successful Japanese summit of Manaslu in 1956. He donated Darjeeling seeds to the Ministry of Agriculture upon returning from the Himalayas, and those seeds became the father plant of Benifuuki. A Japanese black tea cultivar with a mountaineering origin story is not something you encounter often.⁸

The name means red riches and honor, a reference to the reddish color of its younger leaves and the character of the black tea it produces. And for most of the first decade after its registration, that was primarily what it was: a black tea cultivar. But its commercial expansion was limited, and the reason requires a brief detour into Japanese trade history.

Japan had been producing domestic black tea since the Meiji era, originally for export. At its peak in the mid-Showa period, production exceeded 1,500 tonnes annually.⁹ But as Japan's postwar economy rapidly industrialized through the 1950s and 1960s, wages rose sharply. Japanese-produced black tea became expensive relative to Indian, Ceylonese, and Kenyan competitors backed by vast, low-cost plantation systems. Japan could not compete on price.

Before 1971, black tea imports into Japan operated under a quota system that protected domestic producers by restricting how much foreign black tea could enter the country. In June 1971, that quota system was abolished and imports were fully liberalized.⁹ Cheap, high-quality foreign black tea flooded the Japanese market. Domestic production collapsed almost immediately, falling from over 1,500 tonnes to roughly one to two tonnes, consumed only in small quantities locally. The domestic black tea industry came close to extinction.⁹

Benifuuki was developed in 1965 specifically to produce competitive Japanese black tea. By the time it was registered in 1993, the industry it was designed to serve had been essentially dead for over twenty years. The cultivar lingered quietly in warmer corners of Kagoshima and Shizuoka, known among specialists but commercially marginal, earning its reputation as a phantom tea.⁸

Then researchers discovered something unexpected.

When Benifuuki leaves are harvested early and processed as green tea rather than allowed to oxidize into black tea, they produce an extraordinary concentration of a compound called EGCG3"Me, more precisely epigallocatechin-3-O-(3-O-methyl) gallate, also known as methylated EGCG or methylated catechin.¹⁰ This compound is rare in standard Japanese green tea cultivars, and critically, it is destroyed during black tea oxidation by enzymatic action, meaning it can only be preserved and consumed through green tea processing.¹⁰

Research led by Dr. Yamamoto (Maeda) Mari at NARO's Division of Vegetable and Tea Science found that methylated catechins inhibit histamine release from mast cells and reduce the number of high-affinity IgE receptors on mast cells, which are the mechanisms behind allergic symptoms including hay fever and perennial allergic rhinitis. A human intervention study found that 34mg of methylated catechins per day produced significant relief of nasal and eye discomfort compared to Yabukita green tea as a control.¹⁰

The discovery completely shifted how the cultivar was used. Benifuuki went from being primarily a black tea cultivar to being actively promoted as a green tea with specific health properties. Today it is produced both ways, and demand for Benifuuki green tea has grown significantly, driven by allergy-related health interest.

Benifuuki also yields around thirty percent more than Yabukita at harvest, carries high resistance to disease, and can be grown with minimal pesticide use. Its assamica heritage gives it larger leaves than typical sinensis cultivars, a bolder flavor profile, and a higher overall polyphenol content. It is in almost every respect a different kind of Japanese tea plant, and it signals where Japanese cultivar development is heading.

Now we can return to where we began. How can Japanese black tea be made from the same sinensis plant as sencha?

The answer is that variety does not determine tea style. Processing does.

When sinensis leaves are harvested and immediately steamed or pan-fired to halt oxidation, you get green tea. The chlorophyll is preserved, the fresh vegetal and amino acid character is locked in, and the result is the bright, umami-rich cup that defines Japanese green tea.

When exactly the same sinensis leaves are instead allowed to wither, then rolled, then left to fully oxidize before drying, something chemically different happens. The chlorophyll breaks down. The catechins oxidize and polymerize into theaflavins and thearubigins, the compounds that give black tea its dark color and characteristic flavor. And the amino acids, particularly L-theanine, which would have contributed umami to a gyokuro or sweetness to a sencha, instead become flavor precursors during oxidation, transforming into floral, fruity, and honey-like aromatic compounds.¹¹

This is why wakocha, Japanese black tea made from sinensis cultivars, tastes so different from Indian Assam or Sri Lankan Ceylon. It is not just a processing difference. It is a processing difference applied to a plant with a fundamentally different chemical starting point. Sinensis leaves are naturally higher in amino acids and lower in tannins than assamica. When you fully oxidize a sinensis leaf, those amino acids become delicate floral and fruity notes. When you fully oxidize an assamica leaf, its higher polyphenol and tannin content becomes the bold, malty, astringent character that makes Assam tea what it is.¹²

Wakocha is lighter, more floral, naturally sweet, and low in astringency precisely because it starts from sinensis genetics optimized by centuries of Japanese cultivation for green tea production. It can be enjoyed without milk or sugar. It does not need the bitterness-masking that makes milk essential to a strong Assam cup. It is not a lesser black tea. It is a different kind of black tea, with different strengths, produced by applying the universal chemistry of oxidation to a plant that has been cultivated in a completely different direction.¹²

The term wakocha itself, meaning Japanese black tea, was only coined in 2002 by researcher Akasu Jiro, which tells you something about how recent the conscious identity of this style is.¹³ But the practice of making black tea from sinensis in Japan goes back to the Meiji era, when Japan first needed to export tea and briefly competed in international black tea markets.

What is new is not the practice but the appreciation. Japanese tea drinkers and international specialty tea buyers have begun to recognize that sinensis-based black tea has qualities that assamica cannot replicate, just as assamica delivers things sinensis cannot. The two varieties are not better or worse than each other. They are expressions of two different evolutionary paths from the same Yunnan origin, and the tea they produce reflects everything that happened to each of them along the way.