Shade-Growing — Matcha Production Method
Matcha tea plants are shaded for 20–30 days before the spring harvest, blocking 70–90% of sunlight. This suppresses photosynthetic conversion of L-theanine to catechins, tripling or quadrupling L-theanine and chlorophyll concentrations relative to sun-grown tea.
| Measure | Value | Unit | Notes |
|---|---|---|---|
| Shading duration before harvest | 20–30 | days | Varies by producer; some premium lots shade for 30–40 days |
| Sunlight reduction | 70–90 | % | Achieved with traditional reed screens (yotsume-gake) or modern synthetic netting |
| L-theanine increase from shading | 3–5× | vs. the same cultivar grown without shading | |
| Chlorophyll increase from shading | 3–5× | Compensatory response to reduced light | |
| Catechin content change from shading | ↓ 20–30% | Catechin synthesis requires UV; shading reduces total catechins slightly | |
| Typical first-flush harvest timing (Uji) | Late April – mid-May | Shading begins 20–30 days before harvest |
Shade-growing is the most critical differentiating step in matcha production. It transforms the leaf’s chemical profile from a typical green tea (bright, astringent, catechin-dominated) into a shade-characteristic profile (sweet, umami, amino acid-dominated). No other step — not grinding, not steaming, not stone processing — can compensate for the absence of proper shading.
The Two Shading Methods
Traditional (yotsume-gake): Reed or straw screens on a bamboo framework are erected over the tea plants. Light is diffused through the gaps between reeds, creating uneven shade that some producers believe produces more complex flavors. Labor-intensive and expensive.
Modern (synthetic netting): Black polyethylene netting draped over wire frames. More consistent shade percentage, easier installation and removal, lower cost. Dominant in commercial production.
Some premium Uji producers use a hybrid: synthetic netting for the first 2–3 weeks, then switch to traditional reed screens for the final 10 days to impart a specific aroma profile.
Two-Stage Shading in Premium Production
Some high-end matcha producers use two-stage shading: a first period of 60–70% shading (15–20 days) followed by a final period of 85–90% shading (5–10 days). The intense final shading period maximizes L-theanine and chlorophyll accumulation in the young unfurling leaves just before harvest.
Shade Duration Effect on Key Compounds
The table below shows how increasing shade duration affects the major quality-relevant compounds in matcha tea leaves before harvest:
| Shade duration (days) | Chlorophyll increase | L-theanine increase | EGCG change | Umami level | Visual color |
|---|---|---|---|---|---|
| 0 (no shade) | Baseline | Baseline | Baseline | Low | Grassy light green |
| 7 | +50–80% | +30–50% | −5 to −10% | Low–moderate | Brighter green |
| 14 | +100–150% | +80–120% | −10 to −15% | Moderate | Medium vivid green |
| 21 | +150–200% | +150–200% | −15 to −25% | High | Deep vivid green |
| 28 | +200–300% | +200–300% | −20 to −30% | Very high | Deep vivid green |
| 35 | +300–400% | +250–350% | −25 to −35% | Very high | Deep blue-green |
Effect on Tea Plant Physiology
Shading affects the tea plant’s entire metabolism:
- Photosynthesis: Reduced capacity forces the plant to become more efficient
- Stomatal conductance: Changes in gas exchange alter flavor compound distribution
- Root chemistry: L-theanine synthesis in roots continues at the same rate; with less leaf conversion, it accumulates
- Color: Deeper green leaves absorb more light — a visible response to shade
Related Pages
Sources
- Nakagawa M (1975) — Effect of shading on chemical components of tea. Tea Research Journal
- Kito M et al. (1968) — Formation of theanine in tea seedlings. Agric Biol Chem
- Japanese Agriculture Standards — Tencha Production Requirements
- Sakata K (2013) — Chemistry of shade-grown teas. J Agric Food Chem
Frequently Asked Questions
Why is shading essential for matcha production?
Shading triggers a physiological stress response that fundamentally changes the leaf's chemical composition. Without shading, tea plants convert L-theanine to catechins (astringent polyphenols) using UV light. Under shade, this conversion is blocked, and L-theanine accumulates along with chlorophyll and other amino acids. The result is a leaf with dramatically more umami, sweetness, and calm-focus compounds — and dramatically less bitterness.
What materials are used for shading?
Traditional Japanese shading uses 'yotsume-gake' — overhead frames covered with reed or straw screens that diffuse rather than completely block light. Modern producers often use black or dark-green synthetic netting, which is more affordable and weather-resistant. The netting is typically applied in layers to achieve the desired 70–90% light reduction. Some premium producers (especially in Uji) still use traditional materials for the final 1–2 weeks to achieve specific flavor profiles.
What's the difference between shade-grown sencha and matcha?
Gyokuro is shade-grown sencha — tea grown under cover but processed by rolling (not grinding). It shares the elevated L-theanine and chlorophyll of matcha but has a different texture, preparation method, and flavor profile. Matcha requires shading AND subsequent processing into tencha (flat-dried, destemmed leaf) and then stone-grinding. Both are prized shade-grown teas, but the preparation and end use differ significantly.