Eighteen cultivars. That is how many cultivars Ishiyama-san grows on his farm in Sashima, Ibaraki Prefecture. Among tea producers, 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. Its geography allows many different crops to grow. I remember fields of rice, vegetables, and fruit.
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. 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's ties to tea merchants are less strong. Producers can express their own character in their teas without worrying too much about merchants' preferences.
Even among that independent-minded crowd, Ishiyama Tea Factory stands apart.
Eighteen cultivars, and the logic behind them
We think the factor that most shapes how a tea tastes — more than soil, more than weather, more than processing — is 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. Producers working with that many are very rare nationwide.
His father laid the groundwork. The elder Ishiyama studied plant breeding at the prefectural research station, and by the time the son stepped into the fields, the farm already carried many cultivars. What the younger Ishiyama-san explored was another question — what happens when you process each of these cultivars not just as green tea, but as black tea, oolong, withered sencha? The number of cultivars was already high. 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 — processing and tasting the leaves. 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. The bushes are still small, and it will take time before they are ready for a full harvest.
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 experiments with withering, making dozens of trial teas, from black tea and oolong to withered sencha. Ishiyama-san experiments with making black tea and oolong from green tea cultivars. We know other producers making black tea from Yabukita and Tsuyuhikari, but Ishiyama-san's range of trials is unusually broad.
"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.
He liked the taste, 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. The shape and color of the leaves were beautiful.
"It is going to get harder from here, for sure," he says. "But I think it will be fun. 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. We recommend enjoying those year-to-year differences in Ishiyama-san's tea. 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 look forward to tasting what he finds next.
Somewhere in Sashima, a field of small 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.
