Why matcha is grown in the shade

Matcha starts with a decision made before anyone picks a leaf, which is to take sunlight away from the plant. The step is so central that it sits inside the definition. The Japan Tea Central Association's labeling standard defines matcha as tencha ground to a fine powder in a tea mill. It defines tencha as leaf from gardens covered for about two to three weeks before picking, then steamed and dried without rolling. The same document gives gyokuro about 20 days under cover and kabusecha about 7.

What the cover looks like

Shading seems to have begun as protection and only later became a way to shape flavor. The Global Japanese Tea Association says natural reeds were first placed over plants to keep snow off them. Then growers noticed the other effect. Tezumi, a tea seller with a detailed guide to how matcha is grown, dates the development of shading to the mid-1400s. The association's guide to tea kinds says gyokuro is believed to have come from a merchant in 1835 who tried the same shading on sencha leaf. He got a sweeter, richer taste and a deeper green.

Tezumi describes three main methods, listed here from cheapest to most costly.

• Direct cover drapes black cloth on the plants. It blocks around 70% of the sunlight, or around 95% with a second layer. Tezumi says it is only occasionally used for matcha.
• Shelf with synthetic cloth holds the fabric on a canopy above the bushes, so air and moisture move better. Tezumi calls this the most common method.
• Shelf with reeds and straw is the traditional way, with a reed screen first and straw mats added on top.

How dark and how long both vary from one garden to the next. The association puts the usual cut in light at about 85% to 95%. It says the cut is never total, because the plant would not survive without any sun. A 2022 study in the International Journal of Molecular Sciences gives a wider range of 60% to 98%, typically 85%. On time, Tezumi says matcha plants get at least three weeks and some producers go past 40 days. The association's page on kabusecha says at least 20 days for tencha and gyokuro.

What the sun would have done

Most of the explanation comes down to one amino acid, theanine, and where it goes inside the plant. A 2025 review in the journal Plants says theanine is made mainly in the roots. It travels up through the xylem and collects in young leaves. Once there it gets broken down, and part of what it breaks into feeds the making of catechins.

Light is what pushes that change along. The association's plain version says theanine breaks apart in sunlight and turns into catechins, the bitter and astringent parts of the leaf. Block the sun and more theanine stays put. The review is just as direct. It says less light is an effective way to raise theanine, and that shading is commonly used to build it up in young shoots. The association's kabusecha page links theanine to a sweeter taste and stronger umami.

Color follows a separate path through the leaf. With less light, the association says, photosynthesis slows and the plant ends up with more chlorophyll. That makes the leaves a darker, more intense green. Tezumi says the plant builds more chloroplasts and chlorophyll to catch what light is left. It also credits shading with a particular scent called ooika, or shaded aroma.

What one study measured

Numbers help here, and the 2022 study is useful because it compared two levels of shade side by side. Xi Chen and colleagues in Guizhou, China, grew Fuding white tea plants in open air, under 85% shade and under 95% shade. They sampled every five days for about three weeks.

• Theanine was highest at 95% shade, then 85%, then open air.
• Chlorophyll ranked differently, highest at 85%, then 95%, then open air. On day 15, chlorophyll b at 85% shade was 1.4 times the open-air level.
• The four catechins they measured fell under shade, and caffeine rose.
• Leaves grew thinner the longer the shade lasted.
• On day 20, the fresh weight of the leaves was 70.3 mg in open air, 60.86 mg at 85% shade and 36.15 mg at 95%.

Those results show that more darkness does not improve everything at once. Arginine and aspartic acid climbed under 85% shade but dropped over time at 95%. The authors concluded that moderate shade raises amino acid content and excessive shade works against it. This was one experiment on one plant type in one region, so the figures will not transfer neatly to a Japanese garden. The direction of the changes does match what the Global Japanese Tea Association describes.

Why growers put up with the trouble

Shade adds cost to the crop, and the study's falling leaf weights show one way it does. Tezumi adds the labor side. Many shelf-shaded teas are grown as untrimmed bushes that must be picked by hand. Honzu, the reed and straw method, costs considerably more in money and work than synthetic cloth. Tezumi says it also lets more air and moisture reach the plants and gives more complex teas.

Thin leaves also suit what comes next in the making of tencha. Tezumi says the leaves are usually picked a little later so they grow larger. They get deveined during processing, and larger, flatter leaves give more usable leaf and are easier to work with. Taking out the vein then makes the leaf easier to grind. If a seller names its shading method, Tezumi's order from simple to costly runs direct cover, then cloth on a shelf, then reeds and straw on a shelf.