Seimei

Seimei is a matcha-purposed cultivar bred at NARO’s tea research station in Makurazaki, Kagoshima, and registered under the Plant Variety Protection Act in 2020. It was crossed in 1992 from Fushun and Saemidori, and developed to answer a problem the trade had been living with for years: the country’s shade-grown acreage — the raw material for tencha and matcha — was overwhelmingly planted in Yabukita, a cultivar whose yield and tree vigour both decline under cloth, just as matcha and powdered-tea demand rose through the 2000s and 2010s. Seimei is plucked about four days ahead of Yabukita, out-yields both Yabukita and Saemidori under shade, and turns a visibly greener matcha than Yabukita does — the trait its name was chosen for.

Lineage

• Fushun (ふうしゅん) ♀ — the seed parent, contributing strong tree vigour, high yield and cold hardiness. It is itself a Kanaya-line cultivar, bred at the tea station in Kanaya, Shizuoka, and registered under the Plant Variety Protection Act as No. 3697 in October 1993; it is still grown and tested in Shizuoka’s own recommended-cultivar trials as of 2022.
• Saemidori (さえみどり) ♂ — the pollen parent, contributing early budding and strong processing quality. It is also the pollen parent of Kirari 31, bred at a different station from a different seed parent (Sakimidori) around the same period.

This is a controlled cross, not a landrace selection or a sport: both parents are named, and the cross was made deliberately, within NARO’s own tea breeding programme, to combine Fushun’s vigour and cold tolerance with Saemidori’s early budding and quality. Seimei was carried under the trial designation Makurazaki No. 32 (枕崎32号) before it was named. No descendant of Seimei itself is documented here — it is recent enough, registered only in 2020, that no further generation bred from it has had time to reach registration.

History

Why NARO bred it

By the early 2010s NARO’s tea breeders were working against two pressures at once. Processors were asking for cultivars with a flavour genuinely different from Yabukita’s. More pressingly for a matcha-focused programme, production of matcha and powdered tea — which depends on shaded cultivation — had grown roughly 1.4-fold over the preceding decade, while the crop actually growing under that shade cloth remained overwhelmingly Yabukita — planted on roughly three-quarters of the country’s tea fields, much of it ageing, and a cultivar whose yield and tree vigour both suffer under long-term shading. NARO’s stated aim was a high-quality green tea cultivar that held its yield, colour and umami under cover.

Breeding and trial

The cross that produced Seimei was made in 1992, at what was then the National Institute of Vegetable and Tea Science’s tea research division in Makurazaki, Kagoshima — using Fushun, a vigorous and high-yielding Kanaya line, as the seed parent, and Saemidori, valued for early budding and processing quality, as the pollen parent. Seimei was selected in 2000 from that F1 seedling population of 58 seedlings, as the individual F189447, and carried afterward under the trial designation Makurazaki No. 32. A funded regional-adaptation programme — under the agri-food project “Development of tea cultivars with superior colour, flavour and functional components sought by processors, and their cultivation and processing technology” — ran from 2011 to 2015 at NARO’s reorganised Institute of Fruit Tree and Tea Science, examining Seimei’s performance under both open-field and shaded cultivation.

Registration

Seimei’s Plant Variety Protection Act application was filed on 30 June 2016 (application No. 31289) and publicly announced on 30 January 2017 — the date English-language secondary sources such as Ito En’s O-CHA NET give as its “registration year.” The application was granted on 30 March 2020, as registration No. 27874 — the date the Japanese Tea Sommelier’s master list uses instead. Both dates are correct; they mark different stages of one filing four years apart, not a disagreement between sources. NARO’s own adoption target on registration was modest: 500 hectares of new planting within ten years, distributed through licensed nurseries, alongside a cultivation and processing manual issued to coincide with the application announcement.

The name — せいめい, written with no official kanji, though NARO’s own materials gloss it as 清茗 (清, “pure” or “clear,” plus 茗, a literary word for the tea plant) — was chosen for the vivid green colour of the new shoots and the quality of the finished tea.

Characteristics

Seimei buds about five days and reaches first-flush harvest about four days ahead of Yabukita at the Makurazaki breeding station, making it a somewhat early cultivar; in cold districts the gap narrows to level with Yabukita or about a day behind. Tree form is slightly upright, with growth somewhat more vigorous than Yabukita’s. Cold hardiness is better than Saemidori’s, and NARO recommends it for cultivation anywhere from Kanto southward — essentially the same range as Yabukita — though young plants still need frost protection in cold districts such as Saitama, since an early-budding cultivar is exposed to late frost a later one would miss.

Fresh-leaf yield beats both Yabukita and Saemidori across every flush of the season, in open-field cultivation and under shade alike — the trait it was bred for. Disease resistance runs generally ahead of Yabukita’s: medium against anthracnose, strong against ring spot disease, medium against red leaf scorch (赤焼病), and somewhat strong against mochi disease. Cold-damage resistance is mixed — medium against red-wilt frost injury (赤枯), slightly behind Yabukita, but somewhat strong against split-bark frost injury (裂傷型凍害), ahead of it — and the mulberry scale insect (クワシロカイガラムシ) troubles it about as much as it troubles Yabukita.

The cup is where the cultivar earns its purpose. Under shading, both yield and processed quality as sencha exceed Yabukita’s and Saemidori’s; the liquor runs to a bluish-green cast, later flushes lack the “summer tea” off-note that troubles many cultivars past first flush, and umami reads strongly against comparatively low astringency. Made into matcha or powdered tea, it renders a visibly more vivid green than Yabukita does — the specific comparison NARO’s own release materials lead with, and the reason the cultivar exists. It suits tencha, gyokuro and kabusecha as well as ordinary sencha, but tencha and matcha are what it was designed for: NARO built it directly against the gap between rising shaded-tea demand and an ageing, shade-intolerant Yabukita crop. A commercial single-cultivar tasting of it as ordinary sencha describes a dashi-broth savoury note over a lingering fresh-green aroma, with moderate umami and comparatively restrained astringency — consistent with NARO’s own characterisation, if a smaller-stakes showcase than the shaded matcha it was actually bred for.