tea shading cultivation
process / process-tea-shading-cultivation
覆下栽培
Tea shading cultivation is a cultivation technique that shades tea bushes with covering material for a set period from the emergence of new shoots until harvest. It is used for gyokuro and tencha (the raw material for matcha), among other teas.
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Reading the bitterness
Covered cultivation, or shading cultivation, shades tea bushes with covering material for a set period from new-shoot emergence to harvest; it is used for gyokuro and tencha (the raw material for matcha). Tencha is made from new shoots grown under this cover. A source explaining matcha production says that tea bushes are grown in covered gardens to block direct sunlight and reduce astringent constituents, and that only new shoots are picked.
A summary table in the 2018 Manual for Stable Production of Covered Tea states that caffeine increases in new shoots covered for approximately 20–30 days with highly shading material; its remarks classify caffeine as a component of 「苦味・機能性」 (in translation: "bitterness and functionality"). The same table notes a decrease in catechins, classified as 「苦渋味成分、機能性」 (in translation: "bitter-astringent constituents and functionality"), thus distinguishing bitterness (caffeine) from bitter-astringency (catechins) as separate entries. The source does not specify the primary studies underlying this classification.
A 2016 research summary titled 「てん茶・抹茶生産のための被覆方法と品種適性」 (in translation: "Covering Methods and Cultivar Suitability for Tencha and Matcha Production") reports a field trial on the first flush of 'Yabukita'. Starting cover at the 2-leaf stage and applying direct black shade cloth for 20 days, the demonstration trial compared several shade rates and durations: no cover; 85% (20 days); 85% (15 days) followed by 98% (5 days); and 85% (10 days) followed by 98% (10 days). Tencha and matcha production was investigated through a trial designed around these covering treatments.
The same summary table distinguishes individual catechins as well as treating catechins as a group: it states that EGCG (epigallocatechin gallate) does not change under shading, whereas EGC (epigallocatechin) decreases.
In the account of tencha production, EGC content is low while new shoots are young and rises as they mature, but covered cultivation suppresses that rise. For crude tea from the first flush of 'Yabukita', keeping EGC content at approximately 2% or less of dry matter is a production guideline.
Sources for this overview
Checked for this overview: Explanation of reduced astringent constituents under shading and harvesting only new shoots.
Checked for this overview: Summary-table statement classifying increased caffeine as a bitter constituent. / Individual distinction among catechins: unchanged EGCG and decreased EGC. / Suppression of the EGC increase by covered cultivation and the guideline value for crude tea.
Checked for this overview: Design of a field trial comparing multiple shade rates and covering durations.
Other names: 被覆栽培 (ja), 覆い下栽培 (ja)
Follow the connections
tencha →requires→ tea shading cultivation
tea shading cultivation →increases→ caffeine →is a poor universal prototy…→ bitterness
tea shading cultivation →reduces→ tea catechins →are main contributors to→ astringency
Hypotheses and recipe candidates for this entry are on the Japanese page.
Structured claims — open a section to read each claim's confidence, evidence and limits
Composition and content (1)
Scope: New shoots of tea plants -- such as for gyokuro and tencha -- grown under high-shading-rate materials for roughly 20-30 days
Note: A re-investigation of an item deferred in W44 (shading cultivation, "astringency only"). The existing claim covered only the change in catechins (astringent, bitter-astringent compounds) and did not state bitterness explicitly. This claim records that, within the same table of the same manual, the increase in caffeine is classified in the remarks column as "bitterness / functional," while the decrease in catechins is classified as "bitter-astringent compounds" -- a separate item -- showing that the source explicitly distinguishes bitterness from bitter-astringency (astringency).
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process-tea-shading-cultivation —increases→ compound-caffeineHow processing and cooking change it (3)
Note: Tencha's raw tea leaves are new shoots grown under shading cultivation (covered cultivation).
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ingredient-tencha —requires→ process-tea-shading-cultivationScope: Layer: Food. Summary table of tea-plant buds (showing qualitative increase/decrease/no-change classification, not numeric values).
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process-tea-shading-cultivation —reduces→ compound-catechinsScope: Layer: Food. Tencha (matcha raw material), raw tea of 'Yabukita' variety first flush. EGC content is analyzed using analytical instruments such as HPLC.
Note: The description indicates the direction that EGC content increases with new shoot maturity, while shade covering suppresses this increase. Specific measured differences before and after covering (percentage points) are not shown in the relevant section of this material.
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process-tea-shading-cultivation —reduces→ compound-egc