Eighteen cultivars. That is how many tea plants Ishiyama-san tends on his farm in Sashima, a quiet corner of Ibaraki Prefecture where most of the land grows rice, vegetables, fruit — anything but tea. Among the producers we work with, four or five cultivars is typical. Ten is ambitious. Eighteen is something else entirely.
"People tell me I am out of my mind," he says. "But I want to get to twenty-five."
A tea region no one remembers
Ibaraki is not a prefecture that comes to mind when you think of Japanese tea. It sits north of Tokyo, flat and fertile, the kind of land where almost anything will grow. Driving through on our first visit, I remember field after field of different crops — rice paddies giving way to vegetable rows, then orchards, then more rice. No tea in sight. Not a single dark-green hedge row.
The farmers who chose tea here anyway tend to share a certain temperament. Independent. Quietly stubborn. More interested in what the leaf could become than in what the market wants it to be.
Sashima's green teas carry a bitterness that sets them apart. Not a harshness — a presence. It trails behind the umami as it spreads across the tongue, tightening the flavor, giving each sip a sharper outline and a longer finish. In Shizuoka or Kagoshima, tea merchants hold considerable influence over what producers grow, steering them toward particular aromas and liquor colors that fit market expectations. Sashima never developed those ties. The producers here answer to no one but themselves and the leaf.
Even among that independent-minded crowd, Ishiyama Tea Factory stands apart.
Eighteen cultivars, and the logic behind them
The factor that most shapes how a tea tastes — more than soil, more than weather, more than processing — is, in our experience, the cultivar. Each one carries its own ratio of catechin, caffeine, and theanine — the compounds behind astringency, bitterness, and umami. Each one carries its own aromatic fingerprint, encoded in the genetics of the plant before a single leaf is picked. Change the cultivar and you change everything. Leaf color. Bud growth. Harvest window. How the tea responds to steam, to rolling, to heat. A different plant, a different cup.
Ishiyama-san grows eighteen of them. Not three. Not five. Eighteen. Nationwide, you could probably count the producers working with that many on one hand.
His father laid the groundwork. The elder Ishiyama spent years at the prefectural research station studying plant breeding, and by the time the son stepped into the fields, the farm already carried more cultivars than most. What the younger Ishiyama-san added was a question his father had not asked — what happens when you process each of these cultivars not just as green tea, but as black tea, oolong, withered sencha? The number of plants was already unusual. The number of possibilities became vast.
Planting something new every year
A newly planted tea bush takes roughly five years before it yields a real harvest. During that wait, Ishiyama-san watches. He studies how the cultivar responds to Sashima's soil and weather, tests small pickings by the second or third year — rolling the leaves by hand, steeping them, holding the cup to his nose, tasting. Does this one lean toward green tea? Could it become a black tea worth drinking? Is there something in between?
A field of first- and second-year plants. Barely knee-high, thin-stemmed, easy to overlook. Five years from now, these rows will be producing leaf — and Ishiyama-san will finally know what he has.
Managing close to twenty cultivars — each with its own rhythms, its own preferences, its own processing logic — is the kind of work that makes your head swim just thinking about it. I asked him how he keeps it all straight.
"It is a lot," he says, laughing. "Honestly, I am already wondering how I am going to manage it all. But my father is still working, still giving me room to try things. While I have that window, I want to push as far as I can."
His father's breeding knowledge. His own restless curiosity. Between the two of them, the farm has become a living archive of cultivars — and a laboratory for what each one might become.
Two hundred compounds, or six hundred
Oolong aracha made from Kanayamidori — a cultivar bred for green tea, coaxed into something else.
Green tea's aroma is built from roughly two hundred volatile compounds. Black tea and oolong draw on more than six hundred. The floral notes, the stone-fruit sweetness, the trace of spice — all of it emerges when oxidation unlocks what the fresh leaf holds back.
The part worth pausing on: green tea, black tea, oolong — they all start from the same plant. The same leaf. The same chemistry. What separates them is a single process called icho — withering. Harvested leaves are left to oxidize under controlled conditions. How long. At what temperature. With how much airflow. Those decisions, made over a matter of hours, determine whether the tea in your cup smells of cut grass or of ripe peach and roasted grain.
Ishiyama-san has spent years working at that threshold. Dozens of small-batch trials — adjusting the degree of withering across one cultivar after another, tasting, recalibrating, tasting again. Most producers who experiment with oxidized tea start from cultivars bred for the purpose. Ishiyama-san reaches for green tea cultivars — Yabukita, Tsuyuhikari, Kanayamidori — and asks them to become something they were never designed to be. We know a few other producers attempting similar crossovers, but none working at the scale of variation that Ishiyama-san is.
"I get advice sometimes, but the methods are completely self-taught," he says. "Even if someone showed me exactly what they do, I have different equipment, different conditions. It would not work the same way. So I figured I would just find my own path."
In Sashima, some people call him the maverick. He does not seem to mind.
The pan-firing detour
Last year, he tried kamairi — pan-fired tea, a method largely confined to a few pockets of Miyazaki and Saga. The process produces a toasty fragrance that no other firing technique can replicate. Ishiyama-san bought a steel pan specifically to see what that character could do for his oxidized teas.
The aroma was promising. A dry warmth, something between roasted chestnut and scorched grain. But the volume was not there.
"Trying everything is the fun part," he says. "But lately I have tried too many things, and I am starting to wonder — what do I build around? What is my center? The pan-fired tea tasted good. But there is no way to produce enough with that equipment. So I had to let it go, at least for now."
Withered sencha. Oxidized tea. Pan-fired tea. Eighteen cultivars and climbing. The path does not follow a clean line — it branches, doubles back, wanders off. A young producer standing in the middle of it all, bumping into walls, adjusting, planting something new. That seems to be exactly how he prefers it.
A cup that never tastes the same twice
We tasted his Kanayamidori oolong that afternoon. The rolled leaves were dark and tightly wound, with a glossy sheen that made me hesitate before dropping them into the pot. The liquor came out a pale amber — lighter than I expected from leaves that dark — carrying a clean sweetness and a floral lift that lingered well after the cup was empty. Not what you would predict from a green tea cultivar.
"It is going to get harder from here, for sure," he says. "But I think it will be worth it. I have all these cultivars, and some of the ones that never scored well as sencha might actually turn out to be suited for black tea, or for oxidized tea. That potential is just sitting there. Those are the ones I want to find."
There is something in the way he talks about his work — not with bravado, but with a forward-leaning energy. The kind you see in someone who has already decided the harder path is the right one.
Tea shifts with each year's weather. Blending can smooth those shifts out, but single-origin tea made from a single cultivar does not offer that option. The cup you drink this spring will not taste like last spring's. For most producers, that variability is a problem to manage. For Ishiyama-san, it is the point. Every harvest is a new answer to the same set of questions — what can this cultivar do, processed this way, in this year's weather? We have come to look forward to it — the annual surprise of tasting what he has found.
Somewhere in Sashima, a field of knee-high bushes is quietly putting down roots. Another cultivar. Another set of unknowns. Another few years of waiting before anyone — Ishiyama-san included — will know what it can become.