Koshun Tea: The Shizuoka Cultivar Bred for Aroma

by Christian Mauerer, founder of One with Tea, who filmed with tea growers across Shizuoka in May 2025

Koshun tea (香駿) comes from a Japanese tea cultivar that Shizuoka's prefectural tea experiment station bred by crossing Kurasawa with Kanayamidori. Japan's agriculture ministry registered it in 2000 as plant variety No. 8131, with Shizuoka Prefecture as the registrant. Its name says what it is for. The 香 is aroma, the 駿 comes from Suruga, the old province where it was bred, and the prefecture's own research centre titles its fact sheet on the plant "a cultivar to enjoy for aroma."

That aroma is described in Japan as a cooling, refreshing quality that lasts, and as clearly different from Yabukita. It is also the reason the plant is fussy to make. The breeder who led the project wrote that deep steaming is not appropriate for it, because the steam takes the very thing you grew it for. Shizuoka has about 15 hectares of Koshun against 9,990 of Yabukita. Our guide to Japanese tea cultivars shows where it sits among Japan's other tea plants. This page is the reference entry: what Koshun is, who bred it, how it tastes, and how to brew it. We do not sell Koshun, so nothing here is steering you toward a product.

Key Takeaways

• A bred cross, not a chance seedling. Kurasawa as the seed parent, Kanayamidori as the pollen parent, raised at the Shizuoka tea experiment station in Kikugawa and registered in 2000 as No. 8131.
• Aroma is the official selling point. The registration rates the finished tea's aroma, color, liquor and taste as superior and its shape better still, while recording total nitrogen and amino acids as slightly low.
• Do not deep steam it. The lead breeder wrote that deep steaming is not appropriate, since the fresh aroma is the point of the plant.
• It is not a mountain cultivar. The industry guidebook says it suits the whole prefecture. Tenryu sells Koshun, but Shizuoka's own strategy lists name Shizuoka City, Kawanehon-cho and Fukuroi.
• Rare by area, official by status. About 15 hectares in Shizuoka against Yabukita's 9,990, per the prefecture's March 2026 tea report, yet Koshun is one of just two mid-season cultivars on the prefecture's recommended list, the other being Yabukita.

What is Koshun tea?

Koshun is a Japanese green tea cultivar from Shizuoka Prefecture, grown for sencha and picked mid-season, at the same time as Yabukita or a day later. The Shizuoka Tea Industry Association's cultivar guidebook describes a plant with a spreading habit, medium vigor, many even shoots and high yields, whose leaf rolls fine and neat, and whose aroma is distinct enough that the association treats it as a branding cultivar: a tea whose flavor is, in its words, clearly different from Yabukita.

One detail is worth holding on to, because it explains a contradiction you will meet in print. Koshun buds slightly early but is plucked mid-season. A summary table on the association's own sheet prints "early" in the maturity cell, while the body text of that same sheet, the ministry's registration record, the prefecture's research centre and the association's strategy document all say mid-season. Mid-season is the answer.

Koshun at a glance

Attribute	Detail
Written form	香駿 (こうしゅん), also romanized Kôshun or Koushun
Parents	Kurasawa (seed) crossed with Kanayamidori (pollen)
Bred at	Shizuoka Prefectural Tea Experiment Station, Kikugawa, Ogasa district
Plant variety registration	No. 8131, applied 21 October 1996, registered 27 June 2000
Registrant	Shizuoka Prefecture
Breeder's right	Ran its full 25 year term and expired 28 June 2025
Harvest timing	Mid-season, with Yabukita or one day later, though it buds slightly early
Made as	Sencha above all, and not deep steamed
Area today	About 15 hectares in Shizuoka (prefectural estimate, 2023 to 2025)

Where Koshun came from: Kurasawa crossed with Kanayamidori

Koshun was made on purpose, by hand, at a government station. Shizuoka's prefectural tea experiment station at Kikugawa, in the old Ogasa district on the Makinohara plateau, crossed Kurasawa as the mother with Kanayamidori as the father, and selected the seedling that became Koshun. Five breeders are named on the registration: Kuranuki Koichi, Nakamura Nobuyuki, Hidaka Tamotsu, Nagatani Takayuki and Aono Mariko. The same five published the plant's naming paper in 1999, titled, in translation, "Koshun, a new sencha cultivar rich in aroma and flavor."

The paperwork moved at the speed of Japanese variety registration. The application went in on 21 October 1996, was published on 12 March 1999, and registration No. 8131 was granted on 27 June 2000. The breeder's right then ran its full 25 year term and expired on 28 June 2025, which is worth knowing if you read an older Japanese page saying that seedlings may only be bought from prefecture licensees. That was true under the right. The right has since lapsed.

The registration record is also the least romantic description of the plant you will find, and the most useful. Open habit, medium vigor, large bush spread, many shoots at plucking, deep green young leaves, lanceolate mature leaves. Finished product shape rated considerably superior; color, aroma, liquor color and taste all rated superior. Then the line that explains the cup: total nitrogen and amino acids are slightly low. Amino acids are what most Japanese tea drinkers mean by umami, so Koshun was never going to win on thickness. It was bred to win on smell.

What Koshun smells and tastes like

Koshun's aroma is described in Japanese sources as a cooling, refreshing quality that persists, and as obviously different from Yabukita. The industry guidebook words it as a lasting sense of coolness. The prefecture's research centre calls it a distinctive cool-toned aroma with umami and astringency in balance. Nakamura, the lead breeder, reported preference surveys in which tasters rated Koshun highly for strong flavor, good aroma and umami, and in which the aroma was most often read, especially by younger women, as fresh and cooling.

Sellers translate that into plant words rather than flower words. Hagiri, a Shizuoka tea merchant that sells two single-cultivar Koshun teas, one from Tenryu and one from the Fuji Ashitaka slopes, describes both as having a herb-like aroma. Fuji Akiyamaen, a single-cultivar specialist in Shizuoka, calls it a cultivar whose difference you can pick out immediately, with a fresh aroma like incense.

The most detailed tasting notes in English come from Florent, a Japanese tea instructor who writes the Japanese Tea Sommelier blog and buys single-cultivar lots directly from Shizuoka growers. Writing about a Koshun from Mariko in 2015, he found "wild flowers, aromatics herbs with slight menthol aroma," and a cup where, "instead of umami, this is a sweetness closer to sugar that dominates." That second line is the registration's low amino acid reading, tasted. On a Koshun from Tamakawa in the Hon'yama (本山) district he added green apple and something "somewhat reminiscent fennel," and noted that this one "never falls into an overflow of astringency, never tannic, as can sometimes be seen with Kôshun."

If you have read that Koshun smells of jasmine or orchid, treat that as one English retailer's framing. I could not corroborate it in any Japanese source. What the Japanese record says, repeatedly, is coolness and herbs. Japan's tea encyclopedia groups Koshun with Fujikaori and Soufuu as the cultivars with distinctive aroma, and we have written about both.

Why deep steaming is wrong for Koshun

Deep steaming and Koshun work against each other, and this comes from the person who bred it. Writing for the World Green Tea Association, Nakamura states plainly that making Koshun as a deep-steamed tea is not considered appropriate, because its defining feature is the fresh aroma. His fix for a finish that reads slightly astringent is to steam a little longer, but only as far as the aroma will tolerate.

That matters because Shizuoka is deep steaming country. Fukamushi sencha steams the leaf longer than standard sencha, which breaks the leaf down and gives a thick, cloudy green cup with a softer, rounder flavor. It is a wonderful process, and it is what I watched being made at Ichikawa-en in Makinohara, on the same plateau where Koshun was bred. It is also the one process Koshun's own breeder says to keep away from it. Run a cultivar chosen for lasting fragrance through a long steam and you have spent the premium on the wrong thing.

Two more production notes sit in the same place. The guidebook rates Koshun strong against red-blight cold damage and somewhat weak against anthracnose, a leaf disease, while the prefecture's research sheet words those ratings slightly differently, so read them as a range rather than a verdict. Nakamura adds a pest the guidebook leaves out: Koshun is susceptible to mulberry scale and needs careful control. And because the field shifts toward many small shoots as it matures, growers have to plan rejuvenation pruning rather than let it drift.

Is Koshun a Tenryu tea?

Koshun is grown and sold in Tenryu, but it is not a Tenryu cultivar, and Tenryu is not where the record puts its home. We had this row filed as a Tenryu mountain cultivar when we started. Neither half of that survived the sources.

What supports the Tenryu link is real but narrow. Florent, the Japanese Tea Sommelier blogger quoted above, bought and reviewed a hand-picked Koshun from Tatsuyama, in the Tenryu district north of Hamamatsu, in 2015, and a Shizuoka merchant sells a tea called Tenryu Koshun today. What works against it is the prefecture's own planning. Shizuoka's annual tea report lists strategic cultivars municipality by municipality, and Koshun appears for Shizuoka City, Kawanehon-cho and Fukuroi City. Hamamatsu, the city that contains Tenryu, does not list it. In the same 2015 season Florent was buying Koshun from Mariko and from Tamakawa in Hon'yama as well, so Tenryu was one of several districts, not the source.

The mountain half fails more simply. The association's guidebook says Koshun is cold-hardy and high-yielding and therefore suits the whole prefecture, and recommends it to districts that want to build a brand on quality. It was bred on the plateau at Kikugawa, not in a gorge. What is true is that mountain districts like Hon'yama, Kawane and Tenryu are where the carefully made, lightly steamed Koshun lots tend to come from, and that is a statement about growers and processing rather than about the plant.

Worth reading the Tenryu review to the end, too. Florent called that Tatsuyama tea very aromatic, rich, slightly mineral, floral and sweet, with a remarkable length of finish, and then wrote that "the aromatic characteristics of Kôshun nevertheless remain very soft." Koshun's fragrance is distinctive. None of the tasting notes I could find calls it spectacular.

Why Koshun is still rare: 15 hectares

Koshun is rare because almost nobody planted it, not because it failed. Shizuoka's tea report tracks planted area by cultivar, and Koshun goes 10 hectares in 2018, 11, 12, 14, 14, then 15 in 2023, where it has stayed through 2025. Over the same period Yabukita fell from 15,104 hectares to 9,990, out of a prefecture total of about 11,600.

Set it beside its own parents and the scale gets clearer. Kanayamidori holds 88 hectares in Shizuoka and Kurasawa 37, both flat for years. A cultivar bred in 1996 and registered in 2000 has not overtaken either.

Status is the odd part. Fifteen hectares is roughly a tenth of a percent of Shizuoka's Yabukita area, and yet Koshun is an official prefectural recommended cultivar, one of only two in the mid-season class. The other is Yabukita. The association's strategy document explains why a prefecture would carry a plant that small: it is there to be branded, as a tea whose flavor is clearly not Yabukita's, for districts willing to sell it as itself. That is the same argument behind Tsuyuhikari, and it is the opposite of the logic behind the Yabukita problem, which left one cultivar on about six of every seven hectares in Shizuoka.

How to brew Koshun

The only brewing guidance I can source to someone who has tasted many Koshun lots comes from Florent, the Japanese tea instructor behind the Japanese Tea Sommelier blog. For a hand-picked Koshun he wrote that "with this variety, there is no hesitation, the water should be hot." For thicker, machine-harvested leaf he gave 80 to 85 degrees Celsius, which is 176 to 185 Fahrenheit. Hot water lifts aroma, and aroma is the reason you bought this tea. Pushing the temperature down to protect umami makes little sense in a cultivar whose amino acids are officially on the low side.

1. Check the tea is a lightly steamed sencha rather than a deep-steamed one.
2. For hand-picked Koshun, go hot: "with this variety, there is no hesitation, the water should be hot."
3. For thicker machine-harvested leaf, 80 to 85 degrees Celsius, which is 176 to 185 Fahrenheit.
4. If the cup reads thin, raise the temperature rather than the steeping time.

Two practical notes follow from the processing. Koshun is best made as a lightly steamed sencha, so the leaf stays whole and the infusion runs clear rather than cloudy, and it will not behave like the deep-steamed Shizuoka teas most people have met. Start with the standard method in our guide to brewing green tea, then raise the temperature rather than the steeping time.

We do not sell a Koshun tea. One with Tea works in matcha, and nothing I found shows Koshun grown for tencha, the shaded leaf that gets ground into matcha. This is a sencha plant, and a specific one. If you want to taste it, look for single-cultivar sencha from Shizuoka City, Kawane or Tenryu, and check that it is asamushi rather than fukamushi. The photographs in this article were taken in Shizuoka in May 2025, in fields and factories that are not Koshun's.

What stays with me about this plant is how deliberate it is. Somebody crossed two cultivars in the mid nineties, waited years, wrote a paper, named the result for aroma and for the old name of the province, and then the prefecture kept it on the recommended list at 15 hectares because the smell is worth keeping. That is not how most agriculture works. It is very much how the growers we filmed think.

Buying tea for a shop, cafe or studio? We supply organic Japanese tea at wholesale, with the same attention to where each lot comes from. See our wholesale program, or get in touch and tell us what you are pouring.

Frequently asked questions

What does Koshun tea taste like?

Koshun leads with aroma: Japanese sources describe a lasting cooling freshness, sellers call it herb-like or incense-like, and Western tasting notes run to wild flowers, aromatic herbs with a slight menthol edge, green apple and fennel. In the cup it is balanced rather than thick, with a sweetness that reads more like sugar than like the savory umami of a shaded tea, which matches the registration's record of slightly low amino acids.

Is Koshun used for matcha?

No source I found shows Koshun grown for tencha, the shaded leaf that is ground into matcha. Every official description treats it as a sencha cultivar. Some producers also make it as black tea or as a pan-fired tea, which sellers describe but no government or research source confirms.

Should Koshun be deep steamed?

No. Nakamura, who led the breeding team, wrote that deep steaming is not appropriate for Koshun because its fresh aroma is the point of the cultivar. If the finish is slightly astringent he advises steaming a little longer, but only as far as the aroma will bear.

What are Koshun's parent cultivars?

Kurasawa is the seed parent and Kanayamidori is the pollen parent. Both are still planted in Shizuoka, Kanayamidori on 88 hectares and Kurasawa on 37, against Koshun's 15.

When is Koshun harvested?

Mid-season, at the same time as Yabukita or a day later, although the bushes bud slightly earlier. One summary table prints "early," which conflicts with the registration record, the prefecture's research sheet and the association's own body text.

Is Koshun rare?

Yes, by area. Shizuoka records about 15 hectares of Koshun against 9,990 hectares of Yabukita, in a prefecture with roughly 11,600 hectares of tea in total. It is still an official prefectural recommended cultivar, and one of only two in the mid-season class.

Sources

• Ministry of Agriculture, Forestry and Fisheries, plant variety registration database, record No. 8131 (香駿): registration record, in Japanese. Parentage, breeding site, application and registration dates, registrant, the five breeders, official characteristics and quality ratings, breeder's right term and expiry.
• Shizuoka Tea Industry Association (静岡県茶業会議所), cultivar guidebook (茶品種ガイドブック), Koshun page: PDF, in Japanese. Parentage and 2000 registration, mid-season timing, habit and yield, cold and disease ratings, the lasting cool aroma, the name's origin in Suruga, suitability across the whole prefecture, rejuvenation pruning.
• World Green Tea Association (公益財団法人世界緑茶協会), "Koshun, a mid-season cultivar with a flavor unlike any before it," by Nakamura Nobuyuki: article, in Japanese. Preference survey results, the instruction not to deep steam, mulberry scale susceptibility.
• Shizuoka Prefectural Research Institute of Agriculture and Forestry, Tea Research Center, "Tea cultivars bred by Shizuoka Prefecture": PDF, in Japanese. Koshun as a cultivar to enjoy for aroma, parentage, 2000 registration, timing, yield and ratings.
• Shizuoka Prefecture, 静岡県茶業の現状 (The State of Shizuoka's Tea Industry), March 2026: PDF, in Japanese. Planted area by cultivar 2018 to 2025 (Koshun 10 to 15 ha, Kanayamidori 88, Kurasawa 37, Yabukita 9,990), the recommended cultivar list, and strategic cultivars by municipality.
• Nakamura N., Nagatani T., Kuranuki K., Hidaka T. and Aono M. (1999), "Koshun, a new sencha cultivar rich in aroma and flavor," Research Report of the Shizuoka Tea Experiment Station No. 22, pages 23 to 33: scanned paper, in Japanese. The naming record for the cultivar.
• Florent, "Shizuoka 2015: Tenryû," Japanese Tea Sommelier, 28 October 2015: blog post. The hand-picked Tatsuyama Koshun, hot water, the length of the finish, and the judgment that its aromatic character stays very soft.
• Florent, "2015 Shizuoka: Kondo wase, Koshun cultivar from Mariko," Japanese Tea Sommelier, 7 May 2015: blog post. Wild flowers, aromatic herbs, slight menthol, and sweetness in place of umami.
• Florent, "Shizuoka Tamakawa 2015: Koshun," Japanese Tea Sommelier, 6 July 2015: blog post. Green apple and fennel notes, the 80 to 85 degree guidance, astringency in some Koshun.
• Hagiri (葉桐), Shizuoka tea merchant, single-cultivar Koshun listings (in Japanese): cultivar page. Tenryu Koshun and Fuji Ashitaka Koshun, both described as herb-like in aroma.
• Fuji Akiyamaen (富士秋山園), single-cultivar tea shop, cultivar tea descriptions (in Japanese): shop page. Koshun as an immediately identifiable aroma, fresh and incense-like.
• ITO EN, お茶百科 (Tea Encyclopedia), cultivars section: page, in Japanese. Koshun grouped with Fujikaori and Soufuu as cultivars with distinctive aroma.