Rokuro

Rokuro is a sencha cultivar registered in 1953 as Cha Norin No. 9 — one of the first fifteen tea varieties Japan’s Ministry of Agriculture and Forestry ever certified, in the inaugural year of the 茶農林 (Cha Norin) registration system, the same year and the same programme that gave Yabukita its own number six. It was selected from Shizuoka Zairai stock by Sugiyama Hikosaburo, the grower credited with discovering Yabukita, and developed for over a decade at the Shizuoka Prefectural Tea Experiment Station before national registration. Despite that pedigree it never took hold: Shizuoka struck it from its own recommended-cultivar list within two years of the national registration, and it survives today mainly as an entry in old registries rather than as a cultivated tea.

Lineage

• Shizuoka Zairai individual — an individual tree selected by Sugiyama Hikosaburo from indigenous stock, not a controlled cross. No source names the originating garden; the only locality recorded is the tree’s internal plot designation at the experiment station’s foundation-stock ground, “Section 3, Plot 6” (3区6号地).

Because it is a landrace selection rather than a cross, Rokuro has no recorded pollen parent, and no cultivar in this collection or elsewhere is documented as bred from it. Its closest relatives, in the sense of shared origin rather than shared genetics, are Sugiyama’s other named selections from the same registration effort: Yabukita (Cha Norin No. 6) and Koyanishi (Cha Norin No. 8), both registered alongside it in 1953, and Yaeho (Cha Norin No. 17), registered the following year.

History

Tea variety registration in Japan began, as a formal national system, only in 1953. The paper that announced it — 茶業研究報告 (Tea Research Journal) No. 2, published that October — opens by noting that the then Ministry of Agriculture and Forestry (農林省, renamed 農林水産省, Ministry of Agriculture, Forestry and Fisheries, in 1978) had just named its first batch of registered cultivars across several crops, fifteen of them tea: ten green tea varieties (eight for sencha, one for tamaryokucha, one for kamairicha) and five for black tea. Most of these had already been in use for years; formal registration simply gave them an official number. Rokuro was one of the eight sencha cultivars in that first batch.

Its own entry in that paper is terse. It was selected by Sugiyama Hikosaburo and developed between 1935 and 1946 (Showa 10 to 21) at the Ministry-designated foundation-stock plot of the Shizuoka Prefectural Tea Experiment Station — the same institutional programme, over the same years, that also carried Koyanishi through development. Separately, Shizuoka Prefecture’s own records (via the Japanese Wikipedia biography of Sugiyama) show it was already a prefectural recommended cultivar from 1937, partway through that development window, and the same record shows it excluded from Shizuoka’s recommended list again in 1955 — two years after national registration, and the same year Koyanishi was dropped alongside it. A 2013 history of Shizuoka’s cultivar policy, by Nakamura Yoriyuki (中村順行), then director of the Shizuoka Prefectural Tea Research Center, groups Yabukita, Koyanishi and Rokuro together as the prefecture’s Showa-10s (1935–1944) wave of clonal-cultivar promotion, driven by wartime and export-era demand for higher, more consistent yield. Rokuro does not, however, appear by name in that same paper’s later table of Shizuoka’s cultivation area by cultivar from 1954 onward — unlike Koyanishi, which shows a recorded 7 ha that year before it too disappears from the record. Whatever area Rokuro held was evidently too small to itemise, even at the height of its brief prefectural favour, and it was in any case about to be overtaken: by 1972 Yabukita alone held 88% of Shizuoka’s cultivar-planted area.

No release trial data, characteristics bulletin, or trade profile beyond the original registration entry and a handful of reference-list mentions was found for Rokuro in this research. It does surface once outside Shizuoka: the 1961 registration paper for the gyokuro cultivar Himemidori records that ordinary sencha cultivars — 「やぶきた・ろくろう等」 — had until then been put under shade for gyokuro in Fukuoka’s Yame district.

Characteristics

The 1953 registration paper describes Rokuro as medium-maturing (中生), with an intermediate growth habit (樹姿中間形) and strong vigour. Its leaves are elliptical and large, but the bud count is low and the young buds are yellowish-green. Seed genetic purity is noted as high — a trait called out for several cultivars in the same batch — and the paper rates its quality as “good” for ordinary sencha (普通煎茶として品質良好), the same middling rating given to Koyanishi, in contrast to the “excellent” awarded to some others registered alongside it, such as Asatsuyu. One later tea-shop account, describing Rokuro to a retail audience, adds that its liquor runs clear, with a refined astringency balanced against umami — plausible as a description but not independently verified against trial data.

No yield figures, disease-resistance ratings or cold-hardiness data were found for Rokuro in any source consulted, in English or Japanese. What can be said with confidence is only the shape of its story: a competent, unremarkable sencha selection from the same breeder and the same programme that produced Yabukita, formally registered in the same founding year, but never grown at any scale and abandoned by its own prefecture within two years of that registration.