Ooiwase

Ooiwase is the answer Shizuoka gave to a problem it had made for itself. By 1972 the prefecture had 20,492 ha of tea, of which 4,678 ha were planted to named cultivars — and 87.5% of that cultivar acreage was Yabukita. The station’s own release paper opens on the consequences: one cultivar means one narrow window of optimal plucking, which makes timely harvest impossible as holdings grow, and it means the aroma of Shizuoka sencha converges on a single note. The national station had already supplied the late end of a solution, breeding Kanayamidori in 1970 and Okumidori in 1974. What was missing, in the paper’s words, was an early cultivar that could stand comparison with Yabukita. Ooiwase was bred to be exactly that and nothing more: not a novelty aroma, not a specialist tea, just a plant good enough to pick ten days before the standard and sell at the same grade.

Lineage

• Yaeho (やえほ, 茶農林17号) — the seed parent. An early-budding Shizuoka Zairai individual that Sugiyama Hikosaburo, Yabukita’s own discoverer, selected from his garden and had registered in 1954. It supplied the earliness.
• Yabukita (やぶきた, 茶農林6号) — the pollen parent, and the thing the offspring had to match.

This is a controlled cross, which is worth stating plainly because most of the Shizuoka prefectural cultivars of the period are not. Kurasawa, Yamakai, Surugawase and Fujimidori were each pulled as individual selections out of open-pollinated Yabukita seedling stands, with the pollen parent unrecorded and unrecoverable. Ooiwase was made on purpose, from two named registered parents, against a written breeding target. What Yaeho contributed beyond earliness is visible in the same trials: it is one of the most frost-tender cultivars in the Japanese literature, splitting bark on 84.3% of young trees in the very planting the Ooiwase paper followed, and it runs low in soluble nitrogen. The cross kept the earliness and moved most of the way back toward Yabukita on both counts — Ooiwase’s bark-splitting injury rate in that same ground was 13.5%, and its soluble nitrogen ran 2.11% against Yabukita’s 2.17% and Yaeho’s 1.90%.

No cultivar bred from Ooiwase has been located, and none of the sources consulted names it as a parent. Its documented downstream role is not genetic but agronomic: the release paper closes by proposing it as the first term of a four-cultivar harvest sequence — Ooiwase (early), Yabukita (medium), Kanayamidori (slightly late), Okumidori (late) — which is a staggered-harvest management scheme rather than a pedigree.

History

The cross was made in October 1960 at the Shizuoka Prefectural Tea Experiment Station, Yaeho as mother and Yabukita as father, by Oishi Sadao. Seed was sown in December 1961, the seedlings were raised under glass until March 1963 and planted out into the field that April. First selection came in 1967, the chosen tree taking the individual number やえ・や—4; it was confirmed as a second-selection tree in 1970 and propagated by cuttings to build a clonal line. Under the strain name 60-2 it entered the station’s strain-comparison trials from 1971 in the first early-cultivar group and from 1972 in the third, running to 1976. Characteristic-testing trials ran alongside from 1971 at an expert grower’s field in Iwata, from 1974 at the experiment station’s Fuji branch, and from 1975 at a grower’s field in Omaezaki, with further informal plantings in growers’ fields around the prefecture.

The results through 1976 were good enough that the station put the material to the executive committee of the Shizuoka Prefecture Tea Recommended Cultivar Council, which decided to apply for recommended-cultivar status. In January 1977 the council found the strain superior, named it おおいわせ, and adopted it as a Shizuoka recommended cultivar backdated to the 1976 fiscal year. The paper’s English summary says February 1977 rather than January, an inconsistency internal to the document itself; the prefecture’s own later table simply starts the recommendation at 昭和52, 1977.

It was never submitted for national Cha Norin registration, and there is no mystery about why. The 1978 paper describes a cultivar already scheduled for distribution: Shizuoka planned a three-year propagation programme from 1977, striking 150,000 cuttings a year at the nursery of the prefectural tea producers’ co-operative federation’s training institute, the resulting plants to be handed out to suitable districts in the prefecture. The Seed and Seedling Act registration route did not exist until 1978, so a cultivar being distributed the year before was disqualified on novelty regardless of merit — the same door that closed on Kuritawase, Yamakai, Kurasawa and Shizu-7132. Checking the name against MAFF’s 附表１茶農林登録品種一覧, the full table of nationally registered Cha Norin cultivars, finds no entry. Ooiwase holds a prefectural adoption and nothing else.

That adoption has outlasted its contemporaries. A 2013 lecture by the head of the Shizuoka Prefectural Tea Research Center carries a table of the prefecture’s recommended cultivars and their planted area, and Ooiwase’s row runs from 昭和52 (1977) with no closing year, where Surugawase’s and Kurasawa’s both stop at 平成13 (2001). Its area within Shizuoka went 46 ha in 1982, 123 ha in 1989, 141 ha at its peak in 1998, then 120, 118 and 109 ha in 2000, 2002 and 2007 — a little over half a percent of the prefecture’s cultivar acreage, held steady across a quarter century rather than grown or abandoned. The same lecture places it, with Kurasawa and Kanayamidori, among the releases of Shizuoka’s 1965–74 push for higher-yielding, differently-timed, higher-quality cultivars, and the prefecture’s tea merchants’ co-operative still listed it as recommended cultivar number seven in a 2022 consumer column.

It reaches drinkers in small quantities, and in more places than the prefecture that bred it. Shinkoju, the Saitama single-cultivar specialist, sells it as both ordinary and deep-steamed sencha. Oishii Nihoncha Kenkyujo sells a light-steamed Ooiwase grown by Houkouen in the mountainous Ryōkōchi district of Shizuoka City, describing it as the lead-off batter of the first-flush harvest and as a rare single-cultivar tea made in limited quantity each year. Outside Shizuoka it survives in the Kyushu districts its release paper recommended: a Kanoya deep-steamed sencha in Kagoshima, and a tamaryokucha from Sagara village in the Kuma district of Kumamoto, both sold under the kanji spelling 大井早生 that no official document uses.

Characteristics

The earliness is the point of the plant and it is well quantified. Averaged over 1973–76 at the breeding station, Ooiwase broke bud on 26 March against Yabukita’s 5 April and was plucked on 1 May against 6 May — about ten days and about five days respectively, and the second trial block gives the same pair of dates. It is early enough to beat Surugawase by four days at bud-break. Growth habit is intermediate rather than upright, with many branches and a bush that spreads noticeably faster and wider than Yabukita’s: in the first trial block bush spread reached 126.5 cm by the sixth year against Yabukita’s 85.9 cm, and at the Iwata site 142.8 cm against 126.2 cm. Mature leaves are elliptical, glossy green and slightly smaller than Yabukita’s at 21.4 cm² against 22.6 cm². New shoots come up numerous and visibly hairier than Yabukita’s; a 20 cm frame count at first-flush plucking gave 55.7 shoots against Yabukita’s 42.9, at a slightly lighter hundred-bud weight of 37.7 g against 39.5 g. Cuttings root readily — 100% rooting at two months against Yabukita’s 93.3%, and 98.2% survival with a 72.4% successful-seedling rate in the second year, essentially level with Yabukita and far ahead of Yaeho’s 85.0% and 42.6%.

Set against that, the frost exposure is real and the paper does not hide it. Mature-leaf cold hardiness is strong, level with Yabukita in cut-shoot tests down to −15 °C, but resistance to bark-splitting frost injury is only intermediate, and the release paper warns growers off hollows and lower slopes even inside early districts, off hard pruning in the second and third year while the bush is still building its spread, and off any fertiliser regime that keeps young plants growing late into autumn. At the Fuji branch station, a colder site, Ooiwase showed slightly more cold injury than Yabukita in both survey years. Anthracnose it takes about as badly as Yabukita does, and no other disease appeared across the whole programme. Two later studies fill in what the breeding trials could not: a 1982 field survey of bacterial shoot blight found Ooiwase at 18.5% diseased leaves against Yabukita’s 3.5% in one field and 9.5% against 18.8% in the other — a pair of numbers that refuses to collapse into a single rating — and a 2002 laboratory comparison of eight cultivars found the tea rust mite laid more eggs on Ooiwase than on any other, 97.8 per 20 females over three days against Kuritawase’s 34.8 at the other end.

In the cup it is deliberately unremarkable, and that was the specification. Made as sencha it rolls to a fine tight twist with good colour, and the liquor is described in the release paper as a refreshing aroma over a harmonised astringency and sweetness. The station’s panel put it at 108 and 104 against Yabukita’s 100 on the first flush in two successive years in the first trial block, 102 in both years in the third, and slightly below Yabukita on the second and third flushes of 1976 in the first block. Four outside judges from the Shizuoka tea market and Mitsui Norin scored the first flush 101, 98, 104 and 104, and left comments that agree with one another: a refreshing aroma, and a flavour straightforward enough to blend into other teas; a refreshing sweet aroma over a somewhat light taste; a refined fragrance, a tea one would want to handle; a freshness, with aroma and flavour in balance. The chemistry is essentially Yabukita’s — 6.14% total nitrogen against 6.20%, 2.11% soluble nitrogen against 2.17%, 10.70% tannin against 11.94%, two-year averages — and clearly separated from Yaeho’s lower nitrogen and higher tannin, which is where the quality gain over the early parent comes from. Modern sellers describe it in the same register: a young-leaf aroma over a clear golden liquor in the light-steamed Ryōkōchi version, a gentle balance of astringency and umami with good body but modest umami in the deep-steamed one. It is an early tea that tastes like a good ordinary tea, which is a harder thing to breed than it sounds and exactly what Shizuoka asked for.