Tsukasamidori

Tsukasamidori is a mid-season sencha cultivar selected from a single, naturally cross-pollinated seedling in a Shizuoka Zairai stand and registered in 1984 by Yamazaki Yūji, a private tea grower at Tawaramine, in the hill country now folded into Shizuoka City’s Aoi Ward. Its own registration record singles out two things about it: leaf colour markedly darker than Yabukita’s, and disease resistance — particularly to anthracnose, ring spot and net blister disease — well ahead of it. Beyond that official description, almost nothing about it survives. What makes it worth recording at all is less the tea than the timing: a private grower picking out and registering an old-style Zairai seedling as late as 1983 was, by then, working a method the rest of Japanese tea breeding had already left behind for controlled institutional crosses.

Lineage

• Shizuoka Zairai seedling — an individual selection from a naturally cross-pollinated (open-pollinated) seed-grown stand, not a controlled cross.

Tsukasamidori’s own registration text describes it as bred from “在来種の自然交雑実生” — a naturally hybridised seedling of the Zairai population — the same starting material as Yabukita, Asahi and Terakawa-wase. Because it was picked out rather than crossed, it has no recorded pollen parent, and no source found documents any cultivar bred from it in turn.

History

Green tea breeding in Japan had, by the early 1980s, largely moved on from this method. A 2007 retrospective on a century of Japanese tea breeding records that institutional cross-breeding for green tea cultivars began in 1933, lapsed during the wartime and immediate post-war years while individual selection (分離育種) remained the mainstream approach, and then resumed and gathered pace from 1947 onward — Okumusashi (1962) was the first cross-bred green tea cultivar released, followed through the 1970s by Kanayamidori, Unkai and Okumidori, all bred at prefectural or national stations. Against that backdrop, Tsukasamidori is an outlier: a private individual, not a research station, still finding and registering a one-off Zairai seedling in the early 1980s, decades after that approach had stopped being how new cultivars were normally made. It is closer in method to Sugiyama Hikosaburo’s 1908 discovery of Yabukita than to its own contemporaries.

Yamazaki Yūji filed the registration application on 11 January 1983 (application No. 702) and it was granted on 19 March 1984 as registration No. 511, under Japan’s Seed and Seedling Law (種苗法) — the plant-variety intellectual-property statute overhauled in 1978 to align with the UPOV convention, and known today as the Plant Variety Protection Act. This is a separate track from the older, nationally coordinated 茶農林 (Cha Norin) certification that produced Yabukita (No. 6) and its successors: a full register of the 52 Cha Norin-numbered cultivars issued between 1953 and 2003 has no entry for Tsukasamidori, and a Shizuoka tea museum’s own summary of registered cultivars confirms it by listing 司みどり only among the Seed and Seedling Law registrations — one of 59 issued, of which 30 remained active at the time the page was compiled — and not among the separately listed Cha Norin cultivars. The same summary marks it with an asterisk denoting a cultivar whose breeder’s rights have since lapsed.

No source gives a date for when the parent seedling was actually noticed or first propagated, so a selection year distinct from the 1983 application cannot be stated with confidence. The registrant’s address on file — Tawaramine 314, Shizuoka City (now Shizuoka City, Aoi Ward) — is also the breeder’s own, in the same pattern as a cohort of other privately registered cultivars from this period, such as Terakawa-wase and Satō-wase: a grower’s own selection, filed and registered by the person who found it, rather than the product of a prefectural or national breeding programme.

Tsukasamidori’s variety protection did not run its full course. The registration record itself gives its nominal validity period as 18 years, but also records the breeder’s rights as having been extinguished on 20 March 1992 — eight years after registration, not eighteen. No source found explains the discrepancy; it may reflect an early lapse for non-renewal rather than the statutory term actually running out. Either way, the cultivar has left no further trace: it does not appear on My Japanese Green Tea’s, Japanese Tea Sommelier’s or Ocha.tv’s cultivar detail pages, nor in the kana-indexed cultivar dictionaries maintained by Wachaclub or Japan Tea Chachacha, nor in any vendor listing found. No source explains the name either. It may or may not be a coincidence that 司, read tsukasa, also appears in the breeder’s own given name, Yūji (裕司) — but nothing in the record confirms this was the reasoning.

Characteristics

Tsukasamidori is a mid-season cultivar: its own registration record places both budding time and picking time in the 中 (medium) category, the same band as Yabukita, though no source converts that into a specific day offset. What the record does call out, twice, is leaf colour — new growth is described as deep green with a somewhat strong gloss, and “somewhat darker” than Yabukita’s specifically, which the registration document treats as one of the two traits that distinguish it from Yabukita at all.

The tree habit is somewhat upright, with somewhat strong vigour and a somewhat large stool spread; the leaf layer is of medium thickness. First-flush buds emerge with somewhat good uniformity, in somewhat above-average number, and with a large hundred-bud weight — all pointing to a productive if unquantified yield. New leaves are long-elliptical, medium in size and thickness; branch number is medium, internodes are long, branches somewhat thick, and the leaf-attachment angle medium. Rooting from cuttings is recorded as good, which matters for a clonal cultivar’s practical propagation.

Cold hardiness is where the record is most confident: resistance to both red-scorch and blue-scorch winter injury is rated strong, as is resistance to crack-type (split-bark) frost damage — grouped in the source text alongside “excellent cold hardiness” as one of the cultivar’s two headline traits, the other being anthracnose resistance, also rated strong. Resistance to net blister disease and ring spot disease is rated medium in absolute terms, but the registration record specifically flags both as the second distinguishing trait against Yabukita, describing Tsukasamidori’s resistance to them as “extremely strong” by comparison — consistent with Yabukita’s own well-documented susceptibility to ring spot disease.

On the cup, the only account available is the registration record’s own rating: the processed leaf’s shape, colour, aroma, liquor colour and taste are all marked top grade (上). Reported component content shows total nitrogen somewhat high, amino acids high, caffeine medium and tannin low — a chemistry consistent with a leaf pitched toward sweetness and umami over astringency, though no independent tasting note, vendor description or flavour account was found anywhere to confirm or complicate that reading. Beyond the registration bulletin, Tsukasamidori appears to be a cultivar without a public record of ever having been drunk.