Shade cultivation of tea
Japanese method of covering tea bushes to enhance umami and color.
Shade cultivation (覆下栽培) is a Japanese method of tea cultivation in which tea bushes are covered before harvest to reduce sunlight exposure. The technique suppresses the decline in free amino acids and the accumulation of catechins, producing tea with stronger umami, less astringency, deeper green color, and a characteristic aroma known as 覆い香 (ōika). It is primarily used to produce leaves for gyokuro, kabusecha, and tencha, the raw material for matcha.
Quick Facts
- Earliest estimated start
- first half of the 15th century
- Location of earliest evidence
- Okunoyama tea garden, Uji
- Year theanine was isolated
- 1950
- Isolator of theanine
- Yajirō Sakato
Facts from the source article.
History
Before a 2019 soil study, the origins of shade cultivation were inferred from historical records describing covered tea gardens in the second half of the 16th century, though the precise start date remained uncertain. The Jesuit missionary João Rodrigues wrote of tea gardens in Uji where frames were enclosed with reed or straw mats to protect new shoots from frost. In 2019, researchers examined the soil profile of the Okunoyama tea garden in Uji, analyzing carbon content, rice-derived phytoliths, and radiocarbon dates. An increase in rice-derived phytoliths and carbon in a layer dated to between 1396 and 1440 was interpreted as evidence that large quantities of rice straw had been applied, suggesting shade cultivation began by the first half of the 15th century, about 150 years earlier than previously inferred. Covering initially aimed to protect shoots from frost, but growers later recognized that leaves grown under cover differed in color, flavor, and aroma, so the practice developed into a means of controlling quality. From the late medieval period into the Edo period, shade cultivation was restricted to authorized Uji producers, whose economic position later deteriorated under Tokugawa price controls. A major fire in Uji in 1698 destroyed covered gardens and facilities, and because supply became difficult to maintain, producers in surrounding districts were permitted to use the technique, spreading it beyond Uji.
Methods
The covering material, shading rate, start date, and duration vary by intended tea type, cultivar, harvest season, local climate, and desired quality. Traditional gyokuro and high-grade tencha are shaded with high-shading-rate material for about 20 to 30 days; kabusecha is shaded for about 7 to 15 days, while brief covering of about one week may improve leaf color. Traditional materials include reed screens called 葭簀 (yoshizu) and rice straw, a method known as 本ず (honzu) covering. A traditional rule is "ten days under reed screens and ten days under straw": the garden is shaded with reed screens for about ten days, then straw is spread over the screens for another ten days, raising the shading rate to about 98 per cent. Since the late 1970s and early 1980s, black synthetic materials containing carbon have become widely used, often made from polyethylene or polypropylene shade netting. Overhead canopy shading uses a permanent or temporary frame covered with reed screens, straw, mats, or synthetic fabric, and is widely used for gyokuro and tencha. Direct covering, where fabric is laid directly on the bushes, is used for lower-cost production and is common for kabusecha and processing-grade matcha tencha.
Effects
Shade cultivation changes how tea grows, affecting shoot development, yield, leaf structure, color, taste, and aroma. More intense or longer shading makes these traits more noticeable, but it can also cut photosynthesis, slow shoot growth, and stress the plants. With less light, the plant produces fewer carbohydrates and less dry matter in new shoots, and the leaves tend to be thinner than those grown in full sun. A Japanese experiment showed that as shading increased, shoot growth decreased. Longer covering can push back the first and second flushes, moving later growth into hotter or drier periods, and a delayed autumn flush may reduce the number or evenness of shoots in the next year’s first harvest. In one trial, nearly complete shading for about two weeks caused mature leaves to die and fall off, but it did not reduce the following year’s first-flush yield. In open-grown shoots, free amino acids drop while catechins rise as the leaves mature; shading slows both changes, so shaded leaves end up with more umami-related amino acids and fewer astringent catechins. In 1950, Yajirō Sakato discovered theanine in gyokuro, a key amino acid that contributes to umami taste.
Production regions
In the 2025 crop year, Kagoshima, Kyoto, and Shizuoka ranked first, second, and third in tencha production; Mie, Kyoto, and Fukuoka ranked first, second, and third in gyokuro production; Mie ranked first and Shizuoka third in kabusecha production, with Nara and Fukuoka also identified as principal kabusecha-producing prefectures. Kyoto Prefecture, the historical center of shade cultivation, remains a major producer of gyokuro and tencha, using both synthetic overhead coverings and traditional honzu cultivation. The prefectural government supports replacing older bushes with Uji cultivars such as Uji Midori, Kyō Midori, Samidori, Asahi, Uji Hikari, Ogura Midori, Gokō, Komakage, Hōshun, and Tenmyō. Mie Prefecture is particularly associated with kabusecha, concentrated in the north; commercial production there began in 1951, initially with overhead covering, but direct covering spread as a simpler, less expensive method. Nara Prefecture, known as Yamato tea, produces sencha, kabusecha, tencha, and bancha, and is identified as a principal kabusecha-producing region.
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