Part 1 - Cultivating Matcha: The Shading Method
Among Japanese teas, tencha (the raw material for matcha), gyokuro, and kabusecha are grown using a special method called “shading cultivation” (hifuku saibai), in which the new shoots are not fully exposed to sunlight during their growth period. So, what exactly is this shading cultivation?
What is shading cultivation in the first place?
Shading cultivation is a method in which tea farmers, during the growth of new shoots, cover either the entire tea field or the tea bushes directly with shading materials for a certain period of time to grow the leaves. By blocking sunlight from the tea bushes and suppressing photosynthesis, the decrease of amino acids such as L-theanine is prevented, enhancing umami, and the leaves develop a characteristic aroma known as “ooika” (shaded leaf aroma). This is a cultivation method in which farmers skillfully make use of a plant’s pure and basic feature of performing photosynthesis in order to survive.
This shading cultivation began in Uji more than 400 years ago. Originally, the purpose of shading was to protect the new shoots that sprouted in early spring from damage caused by late frost. However, since differences in quality appeared depending on whether frost protection was applied or not, and because high-quality tea was often grown in tea fields with little sunlight, it is said that tea masters in Uji at that time devised it as a “high-quality tea cultivation technique.”
Mechanism of shading cultivation
Plants such as tea bushes grow by using sunlight for photosynthesis. The absorption of light is carried out by chlorophyll. In the case of tea bushes, L-theanine—an umami component and one of the essential amino acids that is taken up from the roots toward the leaves—is necessary for photosynthesis. Through photosynthesis, this L-theanine changes into catechins, which have bitterness and astringency. When there is plenty of sunlight, tea bushes can perform photosynthesis with relatively little chlorophyll and L-theanine, but when light is scarce, they try to grow by using more chlorophyll and more L-theanine for photosynthesis.
Tea farmers take advantage of this mechanism. Shading is carried out in two stages. First, in the initial stage, shading material is used to reduce the amount of sunlight reaching the tea bushes (70–80% light-shielding). The tea bushes then increase chlorophyll and promote the transfer of L-theanine into the leaves in order to grow with the reduced sunlight. Next, in the second stage, farmers increase the shading even further (90% or more). Since photosynthesis becomes more difficult due to the extremely reduced light, the bushes produce even more chlorophyll, and the L-theanine is not consumed, remaining abundantly in the leaves. As a result, as shown in the photo below, the leaves become a vivid, deep green, and the tea leaves grow with mellow umami rich in L-theanine. In addition, shading cultivation produces the unique aroma known as ooika.
Three components that characterize shading cultivation
Tea leaves grown in open fields are exposed to abundant sunlight, making photosynthesis active, which thickens the leaves and makes them firm. L-theanine absorbed from the roots to the leaves undergoes chemical changes during photosynthesis, transforming into catechins. On the other hand, tea leaves grown with shading cultivation under reduced sunlight have less active photosynthesis, and even when the young buds grow larger, they are said to remain as soft as baby earlobes. The transformation of L-theanine into catechins is suppressed, and much L-theanine remains in the leaves. Their green color is very dark due to high chlorophyll content, and their aroma is distinctive.
L-theanine
L-theanine is one of the amino acids unique to tea, an important taste component that constitutes refreshing sweetness and umami. The more L-theanine, the stronger the umami of the leaves. Also, the higher the L-theanine content, the higher the trade value. While there is no fixed standard of percentage, leaves containing roughly 2%–4% L-theanine are considered rich in umami and are highly valued for tea ceremony use.
Chlorophyll
Chlorophyll is the green pigment that plays an essential role in photosynthesis. When tea bushes receive less sunlight, they increase their chlorophyll content to make more effective use of the limited light. This is why the green color of tea leaves grown under shading cultivation becomes deeper.
Dimethyl sulfide
In tea leaves grown under shading cultivation, dimethyl sulfide, a fragrance component with a rich aroma similar to high-quality green laver (aonori), produces the unique fragrance known as shaded leaf aroma (ooika).
Varieties used for shading cultivation
For cultivating tencha (the raw material for matcha), it is important to select varieties suitable for shading cultivation.
In Japan, about 70% of tea production uses the “Yabukita” variety for various types of Japanese tea. While tencha can be made from “Yabukita” under shading cultivation, it does not result in a highly refined flavor as matcha. In Uji, the birthplace of shading cultivation, many varieties suited to shaded tea, such as “Asahi,” “Samidori,” and “Ujihikari,” are grown.
When farmers select varieties, they consider the intended tea type, climatic and geographical conditions, tea field size, and so on. Among these, whether the harvesting season is early (“wase” early varieties), late (“bansei” late varieties), or in-between (“chusei” medium varieties) is an important factor. In warm regions without frost, early varieties are chosen because they grow quickly and can be harvested earlier. In cooler mountain-valley regions, late varieties are chosen because they are resistant to cold and less prone to frost damage. Farmers also intentionally stagger harvest times by choosing different varieties, preventing the picking season from concentration suring the same period.
Asahi
Particularly excellent for tencha. It has a bright, fresh green color, a unique fragrance, and mellow taste. However it is difficult to increase cultivation area because it is an early variety and the harvest period is short. For this reason, it is rare and commands a high price when it is hand-picked. However, when harvested by shears, the yield per unit area is small, so it is said not to contribute much to farmers’ income.
Samidori
Excellent for tencha, with a bright, vivid color, and outstanding fragrance and flavor. Cultivation area is large and production volume is high. Being a medium-to-late variety, its suitable harvesting period is long, and it has high yields, making it favored by farmers. Among Uji-specific varieties, it is the most widely distributed.
Ujihikari
Excellent for tencha. Its leaves are uniform in shape, tender, and bright in color. As gyokuro, they also have fine, well-twisted form and good tightness, with brilliance. It is a medium variety. Its aroma and flavor are attractive.
Tenmyo
A medium variety. Regardless of shading conditions, its color is good, and it is mild, without peculiar flavor, with a rich flavor that is easy to bring out. It tends to develop shaded leaf aroma (ooika) easily. Its yield is high, comparable to “Samidori.” Its quality is roughly equal to “Samidori” and “Asahi.”
Duration of shading period
The harvest of tencha is considered best about 20 days after shading begins. The definition of tencha set by Japan’s tea industry associations also requires a shading period of at least 20 days. In the two-stage shading method mentioned earlier, the first stage is about 10 days, and the second stage is another 10 days, totaling 20 days, which is the textbook explanation. However, in Uji it is often shaded for longer periods.
Basically, the longer the shading period, the greater the effect of shading, and for the reasons described above, higher-quality matcha is obtained. Depending on customer needs, farmers decide whether to keep it around 20 days or longer. At times, however, due to that year’s growth conditions or harvest-season weather, the shading period may end up longer. In mountainous regions where late varieties are grown, farmers may deliberately keep the shading longer to protect tender new shoots from frost damage, sometimes up to 60 days.
Thus, although a longer shading period tends to produce better matcha, sometimes it simply results from circumstances. In such cases, judging quality solely by shading period can be misleading. Nonetheless, compared to other regions, Uji is relatively characterized by longer shading periods. Matcha unique to Uji, rich in L-theanine with sweetness and a high fragrance, is produced under these conditions.
Methods of shading cultivation
Currently, two methods are used: the “tana-gake method,” in which the entire tea field is covered, and the “jikakake method,” in which the tea bushes are covered directly. In the tana-gake method, the mainstream approach today uses black synthetic fiber shade cloth (kanreisha), while the traditional method in Uji uses honzu materials.
Roof frame shading method using reed mats and rice straw
First, a framework of logs and bamboo is assembled around the tea field to form an “ooishitaen” (shaded garden) where shading materials can be applied. For shading, straw mats (komo) woven from rice straw, reed mats (yoshizu) woven from reeds or bulrush bound with twine, and bundles of straw are used. Shading is done in two stages: first, mats of komo or yoshizu are spread like screens over the framework, reducing sunlight. After a period of shading in this condition, straw is then covered on top in the second stage, increasing shading to create an almost completely dark environment. In this environment, leaves become tender with high water content and low fiber.
The photo below shows an ooishitaen using yoshizu. After a certain period, straw is applied on top for further shading. Ooishitaen are highly ventilated, cooler in temperature, and more humid, so new shoots grow slowly.
However, shading with honzu is very labor-intensive, so nowadays it is carried out in only a very limited number of tea fields. Recently, the mainstream method is ooishitaen with frameworks of iron pipes, covered with black synthetic fiber shade cloth.
Roof frame shading method using synthetic fabric screen
In the past, the framework was made of bamboo and logs, but now iron pipes are used. On this framework, black synthetic fiber shade cloth is spread as the shading material. The advantages of the tana-gake method are:
- Like a parasol, there is space between the shading material and the tea bushes, allowing good ventilation and preventing heat buildup.
- Even when strong winds blow, the shading material does not touch the leaves and damage them.
Direct shading method
As in the photo below, this method directly covers the tea bushes with shade cloth. Compared to the tana-gake method, it is lower in cost and can cover larger areas. However, the drawback is that wind may cause the shading material to rub against young leaves, damaging them. This direct shading mothod is widely used in our souced production area such as Kagoshima and Mie prefecture because their fields are very large.
Tea farmers producing only first flush (one harvest per year)
Shading cultivation, which suppresses a plant’s natural activity for long periods, places great stress on tea bushes. To maintain the lifespan of tea bushes, said to be 20–30 years, it is necessary to let them rest for a long period after harvest. In open-field cultivation, many tea fields are harvested three times a year. However, because of this reason, many shading cultivation fields in Kyoto prefecture are used only for the spring harvest of first flush (ichibancha). Farmers cultivating only for ichibancha add further value by hand-picking, supplying tea at particularly high prices even within the Uji region.