Gyokuro also known as (玉露;; Jade Dew), is a fine and expensive type of green tea that differs from Sencha (煎茶) in that it is grown under the shade rather than the full sun for approximately 20 days. The name "Gyokuro" translates as "jade dew" and refers to the pale green color of the infusion. The shading causes the amino acids (Theanine) and caffeine in the tea leaves to increase, while catechin (the source of bitterness in tea, along with caffeine) decreases, giving rise to a sweet taste. The tea also gains a distinct aroma from the covering process. This type of cultivation is also used in producing tencha (碾茶), but records indicate that this process had already been developed in the Azuchi-Momoyama period.
Merchants selling Japanese green tea typically recommend a unique method for brewing gyokuro which differs from typical tea brewing:
- use twice the weight in dry tea leaves for a given quantity of water (e.g. 6 to 10 grams for 180 ml, or 2 to 3 heaping teaspoons for 2 small cups);
- use a lower brewing temperature (in the range of 50°C-60°C (122°F-140°F) instead of 65°C-75°C (149°F-167°F) for sencha; for high-end Gyokuro such as National tea jury rank, a temperature of 40°C (104°F) is recommended.);
- a longer steeping duration, at least for the first infusion (90 seconds instead of 1 minute for sencha).
Since gyokuro is typically steeped at such a low temperature, sources may recommend pre-heating both the pot and cup to maintain the warmth of the tea as one drinks it. One usually drinks gyokuro very slowly to savour its distinctive flavour.
Gyokuro is one of the most expensive types of sencha available in Japan. The name comes from the product name given to the tea by the Yamamotoyama Tea Company. The tea was first discovered by Yamamotoyama's sixth owner, Yamamoto Kahei, in 1835 (Tenpō year 6). The process was completed by another manufacturer at the start of the Meiji period. The greatest appellation of Gyokuro is Yame, (八女) in Fukuoka Prefecture in terms of both quality and quantity. More than 40% of Gyokuro is produced in Yame, and in the national tea jury in August 2007, Gyokuro of Yamé held all the ranking positions from 1st to 26th as the best Gyokuro.(result of National tea jury in 2007, in Japanese) The Uji district is the oldest Gyokuro-producing region in Japan. Gyokuro should not be confused with "Tamaryokucha (玉緑茶)," a tea produced in the Kyūshū region. Tamaryokucha also has a sweet flavour, but its production process differs from that of gyokuro.