Okumusashi

Okumusashi is a late-budding, cold-hardy Japanese green tea cultivar bred in Saitama Prefecture from a controlled cross of Sayamamidori and Yamatomidori, registered in 1962 as Cha Norin No. 26 (茶農林26号). It is one of the earliest cultivars in the Japanese tea registry produced by deliberate crossing rather than selected from a zairai (landrace, seed-grown) stand — the release paper itself makes a point of this, noting that until then no Japanese green tea cultivar had been bred by crossing at all, only black tea. It was developed specifically to extend the growing season in the Sayama district: alongside Yabukita and Sayamamidori, which both pick in early-to- mid May, Okumusashi buds and picks roughly ten days after Yabukita and four after Sayamamidori, spreading the harvest and reducing frost risk for growers working the cooler, comparatively northern Kanto climate.

Lineage

• Sayamamidori (さやまみどり) ♀ — the seed parent. An early Saitama cultivar, itself selected from zairai seedlings and named around 1953; in the Okumusashi release paper it appears, alongside Yabukita, as one of only two named cultivars then planted in any quantity in Saitama.
• Yamatomidori (やまとみどり) ♂ — the pollen parent. Selected in Nara, according to the Japanese Tea Sommelier’s registry list, from Nara zairai seed; in the Okumusashi trial data it is the latest-picking of the four varieties compared, the trait Okumusashi was crossed to inherit — though its cold hardiness is rated 大, no higher than Yabukita’s or Sayamamidori’s, where Okumusashi alone is rated はなはだ大. It does not appear to have had a wide cultivation history of its own outside its use as a breeding parent and, later, as a genetic-resource line in tea-breeding research (it has since turned up in studies of tea polyploidy and self-incompatibility genotypes).

This is a controlled cross, not a landrace selection: the seed and pollen parents were deliberately combined by hand at a named experiment station, and the resulting seedling population was individually selected over roughly fifteen years before the line was fixed and registered. No descendants of Okumusashi are documented in the sources consulted, and it does not appear as a parent anywhere in the Japanese Tea Sommelier’s master cultivar list.

History

The cross was made in 1947 (Showa 22) at the Ministry of Agriculture and Forestry’s Kumagaya Agricultural Improvement Experiment Station, Toyooka trial site, using Sayamamidori as the seed parent and Yamatomidori as the pollen parent. Crossing and the first round of individual selection were led by Sanui Hajime, assisted by Ozawa Keiji, Fuchinoue Yasumoto and Tanaka Mankichi. F1 seed collected the following year was sown in 1948, and from the germinated population the researchers began tracking, from 1949, individuals with blue-tinted young shoots and strong root and shoot growth.

A single line was fixed as the first-selection tree in 1950 and moved to the main field in 1951 to begin a second round of individual selection. That same year the Kumagaya station was abolished, and the trial — by then a Ministry of Agriculture and Forestry-designated tea-breeding programme — was newly attached to the Saitama Prefectural Tea Research Institute (埼玉県茶業 研究所), which carried the line forward and eventually authored the release paper. Selection continued there from 1952, and in 1954 the line was confirmed as the second-selection tree, given the working strain name 22-131, and switched to vegetative (clonal) propagation for formal line-comparison trials. It was planted out for full comparison in 1956, with yield, quality and cold resistance as the trial’s main measures.

Results were reviewed at the 1959 national tea-trial research liaison conference, where the line was approved as a registration candidate; the following years were spent bulking up planting stock. It was registered in 1962 as the green tea cultivar Okumusashi, Cha Norin No. 26, with Matsumoto Takeo — who had taken over as the project’s lead by then — as first author of the release paper, alongside Fuchinoue, Yonemaru Tadashi and Tanaka. Fuchinoue and Tanaka had stayed with the line since the Kumagaya days; Yonemaru joined in 1952, under Tsutsumi Jiro, who led the project through the selection and line-comparison years.

The release paper’s afterword makes a claim worth taking at face value: that in black tea, most Japanese cultivars were already produced by crossing, but that until Okumusashi no Japanese green tea cultivar had been — every green tea cultivar to that point had been a single-plant selection out of a zairai stand, Yabukita included. Whether or not it was literally the first, the authors framed Okumusashi as a proof of concept, that crossing could produce a workable green tea cultivar and not just a zairai selection, and as filling a specific gap in the Kanto growing calendar: with Yabukita, Sayamamidori and now Okumusashi, growers in Saitama had an early, a medium and a late cultivar to spread their harvest and labour across.

Characteristics

Okumusashi is a late-budding cultivar: in the release paper’s multi-year trials it picked roughly ten days after Yabukita and four to five days after Sayamamidori, placing it mid-rank among the late varieties available at the time. Growth habit is upright and the plant grows large, with branches somewhat thicker than Yabukita’s and shoots that sit slightly higher on the bush. Mature leaves are a dark, glossy green — noticeably deeper in colour than Yabukita — elliptical rather than long-oval, and slightly smaller in area. Vigour is strong and the paper records no notable pest or disease damage through the trial period, though fruit-set (結実性) is low. Yield ran somewhat behind Yabukita in the 1962 comparison: 82.8 kg/10a of leaf across first and second flush (one-bud-three-leaf picking) against Yabukita’s 89.2 kg/10a.

Cold hardiness is the cultivar’s defining trait and the reason it was bred at all. Osmotic penetration-value testing (浸透価, measured in atmospheres) showed only a modest edge over Yabukita — 25.8 to 28.7 against Yabukita’s 23.8 to 28.3, across three winters from 1957 to 1959 — but field observation told a sharper story: Okumusashi showed almost no leaf drop or cold injury where Yabukita did, and, the difference the paper leans on hardest, it came through abnormal winter dry spells with barely any desiccation damage while Yabukita suffered considerably. On the strength of that, the authors recommended it for Saitama’s Sayama tea district and the wider Kanto region generally, rather than for Shizuoka or districts further south or west.

On the cup, the trial’s tasting panel scored Okumusashi’s leaf shape as slightly inferior to Yabukita’s — the thicker leaf and coarser internodes mark it down on appearance — but rated its aroma and taste a little higher in both flushes (94.2 against 92.9 points for first flush, 86.0 against 83.5 for second, on the paper’s own 100-point scorecard). Aroma was singled out as a particular strength, described as highly fragrant. All of this was recorded for sencha; the paper does not address tencha, gyokuro or other processing styles, and none of the specialist cultivar guides or vendor references consulted for this record mention Okumusashi being grown for anything else, or, for that matter, mention it at all. Outside its own registration paper and the master registry list, it appears to be a largely forgotten cultivar today.