The Yabukita position
Yabukita accounts for the large majority of Japan’s tea planted area — a share high enough that Japanese green tea as a category is substantially a description of what one plant does under various processing regimes. There is nothing sinister in how it happened. The cultivar performs well across a wide range of Japanese conditions, it yields reliably, it makes good sencha, it was distributed through an effective extension system, and a grower choosing it was making a sound individual decision every time. The concentration is the sum of a great many reasonable choices, which is the characteristic shape of this kind of problem. It is worth being precise about what the concentration means. It is not that Japan has few cultivars — the national register holds dozens, and this catalogue records many of them. It is that the register and the planted area have come apart, so the diversity exists on paper and in research stations rather than in fields.
What concentration costs
A single clone across a national planted area meets any new pressure with a single response. If a pest or a pathogen does well on it, there is no fraction of the crop that resists, and the industry’s exposure is total rather than partial. Climate adds a second and subtler exposure. Budding date is a cultivar property, so a country planted overwhelmingly to one cultivar has one budding date, and a warm February followed by a March frost hits the whole crop at the same moment rather than a portion of it. Diversity of budding date is, in effect, an insurance policy that a monoculture has cancelled. There is a third cost that is commercial rather than biological. If nearly all of a country’s tea is one plant, then nearly all of it can be blended together, and the individual producer has little to differentiate with — which is precisely the pressure that produced the Japanese aroma cultivars. Concentration reduces agronomic resilience and market variety at the same time.
The same shape elsewhere
TeaHQ's own reading of well-attested general knowledge, with no single source behind it.
Japan is the extreme case and not the only one. Sri Lanka’s planted area leans heavily on a small number of TRI clones, with TRI 2025 grown across every elevation band, so the island’s celebrated regional differences are largely elevation, climate and manufacture rather than plant. Taiwan’s high-mountain oolong sector rests overwhelmingly on Qing Xin, a difficult, disease-prone, low-yielding plant that growers persist with because nothing else gives quite the same cup. Kenya’s enormous output runs on a few dozen numbered clones. Assam and East Africa are further along in planting clonal blocks of several selections rather than one, which spreads the risk without recovering the variability of a seed population. Each of these is a different degree of the same structure: a small number of clonal identities carrying a national industry, with the older seed-grown material either gone or economically marginal.
Why replanting does not fix it
The obvious remedy — plant more cultivars — collides with the economics of establishment. A field takes several years to come into bearing and costs money throughout, so replanting is deferred wherever capital is short, which is nearly everywhere. And when a grower does replant, the rational choice is the cultivar with the best-established performance record, which is the one that is already dominant. Diversification is therefore a decision that costs an individual grower money to solve a problem they do not experience individually, which is the definition of a collective action problem. The interventions that have moved the needle in other crops are the ones that change the individual calculation: replanting subsidies, assured offtake for a less-established cultivar, or a market that pays a premium for a named alternative. The last of these is the one a speciality market can actually supply, and it is the strongest practical argument for buying single-cultivar teas from plants that are not the dominant one.
What is held in reserve
The counterweight to a narrow planted area is a germplasm collection: the research stations of the producing countries maintain living collections of cultivars, selections and wild and landrace accessions that are not commercially planted. That is where the diversity that has left the fields is kept, and it is the material every future breeding programme will draw on. It is also, in tea, unusually well complemented by the fact that old seed-grown stands are still standing in productive fields in China, Georgia, Vietnam and parts of India, so a good deal of the genetic base is still in the ground rather than only in a collection. That advantage is not permanent. Old stands are replanted, abandoned or built over, and the material in them is not recorded anywhere. TeaHQ records landrace populations as catalogue entries in their own right partly for this reason: naming a thing is the minimum precondition for noticing when it goes.
What a drinker sees of this
Very little directly, and something indirectly. The visible symptom is a category that tastes narrower than its reputation: a national style whose variation comes almost entirely from processing and terroir because the plant is held constant. The invisible symptom is risk, which shows up as a bad year rather than as a flavour. What a drinker can do about it is limited and real. Buying single-cultivar teas made from something other than the dominant plant supports the growers who took the risk of planting one, and asking a vendor which cultivar a tea is made from creates the demand signal that makes a cultivar worth naming. Neither of those is a solution to a structural problem in an agricultural industry. But the cultivar catalogue on this site exists partly to make the question askable, and a question that nobody can formulate never gets asked.