Okuharuka

Okuharuka is an extremely late-budding, cold-hardy sencha cultivar bred at Saitama’s prefectural tea research station from a controlled cross of two unreleased internal breeding lines, Saitama 20 and Saitama 7. It is the newest cultivar in Saitama’s long-running programme to breed tea that can survive winters at the northern edge of Japan’s tea belt — the same programme that produced Okumusashi (1962), Sayamakaori (1971) and Fukumidori (1986) — and it pushes the programme’s usual strategy further than any of those three: rather than only tolerating cold, it avoids the worst of it outright by budding roughly a week and a half after Yabukita, late enough to sit out most of the April frost window before it flushes at all. Its other defining trait is unrelated to hardiness: a sweet, cherry-leaf aroma, reminiscent of the pickled sakura leaf used in sakura mochi, that the cultivar’s own release paper attributes in part to a high coumarin content in the leaf.

Lineage

• Saitama 20 (埼玉20号) ♀ — the seed parent. An unreleased internal Saitama breeding line, not itself a registered cultivar. Per the release paper’s own pedigree chart, Saitama 20 is a cross of Sayamamidori (さやまみどり) × Yamatomidori (やまとみどり) — the identical parent combination used for Okumusashi (Cha Norin No. 26, 1962). The sources consulted do not establish whether Saitama 20 is a sibling selection from that same original cross or a separate, later cross of the same two parents; either way, it contributes late budding and high yield.
• Saitama 7 (埼玉7号) ♂ — the pollen parent. Also an unreleased internal Saitama line, descended from Yabukita through two successive generations of open (natural) pollination, via an intermediate line recorded in the pedigree chart as 56G1-99 — which the Saitama Prefectural Tea Research Institute has since corrected: a notice in 茶業研究報告 No. 139 gives that line’s correct designation as 5507 (埼玉13号, Saitama No. 13). It contributes comparatively early budding and strong cold hardiness.

This is a controlled cross, not a landrace selection, but an unusual one for how far back its named ancestry sits: neither parent was ever released under its own name, so Okuharuka’s documented pedigree runs two generations deep into Saitama’s breeding programme before it reaches a cultivar anyone would recognise — Sayamamidori and Yamatomidori on one side, Yabukita (twice removed) on the other. No descendants of Okuharuka are documented in the sources consulted; registered only in 2015, it has not yet had time to be used as a parent itself.

History

The cross was made in 1975 at what the release paper calls the Saitama Prefectural Agriculture and Forestry Research Center’s Green Tea Laboratory — the station is once again the Saitama Prefectural Tea Research Institute (埼玉県茶業研究所) today — using the high-yielding, late-budding line Saitama 20 as the seed parent and the cold-hardy, somewhat-early line Saitama 7 as the pollen parent. Seed was collected and sown in 1976, seedlings were planted to the field in 1978, and individual selection ran through 1982. From 1986 the selected line entered the station’s 34th group of clonal comparison trials (栄養系比較試験第34群), where its cultivation characteristics first stood out.

From 2002 the line — by now carrying the working name Saitama 42 (埼玉42号) — was entered into the 10th group of Japan’s national tea strain-adaptability trial (系統適応性試験第10群), run in cooperation with 14 partner institutions: NARO’s Vegetable and Tea Science Research Institute, and prefectural tea research stations in Shizuoka, Mie, Gifu, Shiga, Kyoto, Kagawa, Kochi, Fukuoka, Saga, Nagasaki, Kumamoto, Miyazaki and Kagoshima. Alongside general adaptability, these trials ran dedicated characteristic-evaluation tests for bark-split frost injury and for blister blight (mochi disease) resistance. In parallel, from 2002 to 2011 the home station in Saitama ran its own cultivation and processing trials. By the end of that decade Saitama 42 was judged cold-hardy and well suited to high-quality sencha.

The line was approved as a registration candidate by the Vegetable and Tea New Cultivar Candidate Examination Committee’s tea subcommittee in January 2012, and by the full committee the following month. In March 2013, under the name Okuharuka, a cultivar registration application was filed under the Seed and Seedling Act (種苗法) — Japan’s Plant Variety Protection Act — and the application was published on 5 July 2013. The release paper, received by the journal in June 2014 and published in December 2014, reports the application and its publication but not a registration grant, because none had yet occurred. The MAFF Plant Variety Protection database records the grant itself: application No. 27958, filed 5 March 2013, published 5 July 2013, and registered as No. 23946 on 11 March 2015 in the name of Saitama Prefecture. See the conflicts note in the frontmatter for the full reasoning.

The named authors span the full life of the programme: current station staff Nakajima Kenta, Miyazaki Yasuhiro, Honda Yusuke, Sakai Takashi, Tanaka Eri, Sasaki Koji and Takahashi Atsushi (corresponding author) are joined by five researchers credited as “formerly of the Saitama Prefectural Tea Experiment Station” — Fuchinoue Yasumoto, Kitada Kaichi, Okano Nobuo, Kyogoku Hideo and Uchino Hiroshi. Fuchinoue, Kitada and Okano also appear as co-authors on Fukumidori’s 1987 release paper, tying Okuharuka directly to the same generation of breeders who built Saitama’s earlier cold-hardy cultivars.

The name

The release paper explains the name directly: “‘Okuharuka’ (おく春香) is named because it is a late-budding cultivar with an aroma like cherry leaves that evokes spring” — pairing おく, the conventional prefix Japanese tea breeders use for late-budding cultivars (as in Okumidori, Okuyutaka and Okuhikari), with a reading of はるか as 春香, “spring fragrance.”

Characteristics

Okuharuka’s growth habit is described as slightly spreading with strong vigour at the home station; mature canopy spread outgrows Yabukita’s, though in years two and three after planting it actually trails Yabukita, Sayamakaori and Kanayamidori at most of the national trial sites, catching up only later. New leaves are larger than Yabukita’s and somewhat slender, pale green, with less waviness at the leaf margin; leaf angle and shoot down are both rated “medium,” the same as Yabukita.

Budding is extremely late — the release paper’s own top category, 極晩生. At the Saitama breeding site it buds and is picked 9 days after Yabukita on a four-year average; nationally, across 13 trial prefectures, picking runs 6 days after Yabukita. Year-to-year variation in picking date is comparatively small (a 3-day spread across the four-year home trial, against an 8-day spread for Yabukita over the same years), which the release paper reads as the cultivar being less exposed to season-to-season swings in spring temperature. Yield is a clear strength: 666 kg/10a first flush and 541 kg/10a second flush at the home station, ahead of Yabukita’s 500/482 kg/10a and roughly level with Sayamakaori’s 660/527 kg/10a; the national trial average tells the same story at smaller scale.

Cold hardiness is the trait the cultivar was bred for, and the trial data back it convincingly. At the home station, spring frost injury to new shoots ran at 5% for Okuharuka against 36% for Yabukita and 21% for Sayamakaori — largely because Okuharuka’s buds are often still dormant when the April frost window passes; a frost-fan trial found 0% of its buds had even emerged by 13 April, against 61% of Yabukita’s. Winter dry-cold and red-scorch damage were rated 1.0–1.2 on a 1–5 scale for Okuharuka, against 2.5 for Yabukita and, on the dry-cold measure specifically, 2.3 for Sayamakaori — a real edge over the cultivar previously treated as Saitama’s cold-hardiness benchmark. In a dedicated bark-split frost injury trial run at the Kagoshima Prefectural Tea Experiment Station, Okuharuka was rated “strong,” matching Kanayamidori — the other cultivar conventionally cited as Saitama’s cold-hardiness benchmark alongside Sayamakaori — and ahead of Sayamakaori’s own “fairly strong” rating in the same trial.

This is worth weighing against Shinkoju’s marketing claim that Okuharuka is “国内で最も寒さに強い品種” — Japan’s most cold-hardy cultivar. That line appears on Shinkoju’s cultivar-index page rather than its dedicated Okuharuka page, and the trial evidence gives it real support as far as it goes: within its own release paper, Okuharuka does outperform Sayamakaori and matches Kanayamidori — the two cultivars other sources in this collection treat as the standing cold-hardiness benchmarks — on several specific, quantified measures, and it comfortably outperforms Yabukita on all of them. What the release paper does not do is test Okuharuka against every cold-hardy cultivar bred in Japan; it was never run head-to-head against Okumusashi or Fukumidori, Saitama’s own earlier cold-hardy releases, in any comparison found for this record, let alone against cold-hardy cultivars bred outside Saitama. “Most cold-hardy in the trials Saitama has actually run” is a defensible reading of the evidence; “most cold-hardy in Japan,” taken literally, is a claim the sources here do not establish.

Disease resistance is more mixed. Field trials found anthracnose and ring spot (gray blight) resistance somewhat better than Yabukita’s. Blister blight (mochi disease) is a genuine weak point: the release paper’s own summary rates Okuharuka “somewhat weak” against Yabukita’s “weak,” but the underlying diseased-leaf counts from the dedicated Shizuoka trial ran higher for Okuharuka than for Yabukita in the worst years (56.0 against 19.3 diseased leaves per 10 plants in 2005; 104 against 40 per m² in 2006), so it is fair to call blister blight the cultivar’s clearest disadvantage regardless of the paper’s own framing. Red scorch (bacterial shoot blight) is also somewhat weak, and resistance to the tea scale insect (クワシロカイガラムシ) sits at about the same level as Yabukita’s. In cultivation notes, the paper says anthracnose and mochi disease control are generally unnecessary in cold tea districts but do need attention in warmer or mountainous ones.

Chemically, new-shoot total nitrogen and amino-acid content both run higher than Yabukita’s and Sayamakaori’s in both flushes, while tannin runs lower; caffeine and fibre are similar across all three. On the cup, Okuharuka is built around its cherry-leaf aroma — the paper links it to coumarin content in the leaf — layered with rich umami and sweetness. In a five-year sensory panel at the home station it scored ahead of both Yabukita and Sayamakaori overall, on both first flush (44.3 against 40.9 and 39.3, out of a 50-point scale) and second flush (25.8 against 23.6 and 24.0, out of a 30-point scale). That result did not hold everywhere: across the 11 sites that ran both adaptability and characteristic trials, only 4 rated Okuharuka’s first-flush quality above Yabukita’s, though 9 rated its second-flush quality above Yabukita’s. Processing trials found that short steaming (about 30 seconds) draws out the cultivar’s shape, colour and aroma best, while the more standard 60-second steam favours liquor colour and taste instead — meaning the deep-steamed (fukamushi) style some specialist retailers sell it as is likely to mute the very aroma the cultivar is bred to showcase, while a lighter steam shows it at its most distinctive.

The release paper recommends Okuharuka for Kanto and the cooler districts north of it, and for mountainous and semi-mountainous tea country nationwide, on the strength of its cold hardiness and frost avoidance — it performs well even in tea gardens with no frost fans installed, and can be autumn-pruned in cool districts where existing cultivars need spring pruning to dodge cold damage. Growers who buy in Yabukita leaf can use its late pick to spread processing-season labour further into the year. Its late-season growth is vigorous enough that, in regions picking only through second flush, summer and autumn pruning to control overgrown shoots is described as essential.