Yuzu Citron (ユズ)
Yuzu citron (pronounced "yuzu"; scientific name: Citrus junos, synonym C. ichangensis x C. reticulata var. austera) is a rutaceous evergreen tree. It produces a citrus fruit.
Summary
Also called honyuzu, it has a relatively large fruit and the surface of the pericarp is rough. The fruit is small, and it differs in type from the precocious hanayuzu (hanayu, issai yuzu, citrus hanayu). Both are called yuzu in Japan, and generally the two are confused with one another. Many fruits have abundant seeds.
Japan is the top country in terms of consumption and production. Among citrus fruits it is relatively resistant to cold, and it's one of the few types that can grow naturally in the Far East. It has a strongly acid taste and scent. The tree is an evergreen of medium size that's widely cultivated in the south of the Tohoku region in Japan. The floral language is said to be "healthy beauty."
Also, as well as the custom called 'Komorigaki' of the persimmon, in which the harvest leaves some of the fruit, the yuzu citron has the same custom, called 'Komoriyuzu' in some regions.
It's known as a slow-growing tree and is sometimes called 'sixteen years of silly yuzu citron.'
Therefore, it takes more than ten years until fruition for cultivation from the seed, so in order to shorten the period till fruition, it can be possible to harvest after a few years by grafting Poncirus trifoliata.
History
Honyuzu is said to be native to the central and west areas of China and the upper reaches of the Yantze River. It is said that it was propagated to Japan directly or via the Korean peninsula, but that isn't certain. Only a statement remains in the history book that it was cultivated during the Asuka and Nara periods.
There are three main groups of yuzu citrons currently being cultivated in Japan, such as the 'Mokuto group' as honyuzu, the 'Yamane group' as early-fruition varieties and 'Tadanishiki' as a nuclear (seedless) yuzu citron.
The fruit of 'Tadanishiki' is smaller and has slightly less fragrance than honyuzu, but it has fewer thorns and almost no seeds. It has a lot of juice, so Tadanishiki is easier to cultivate than honyuzu (whose long thorns may hurt the fruit due to strong winds and ultimately reduce the commercial value).
Hanayuzu is said to be native to Japan, but the details aren't known.
The origin of yuzu is '柚(yòu)' in Chinese. However, the word currently indicates 'citrus grandis' in Chinese. Currently, '香橙' (pronounced 'xiāngchéng' in Chinese) indicates the yuzu citron, but it isn't known why the word has changed. The reason '柚' changed to '柚子' in Japan largely depends on the usage as vinegar in ancient times. It was said that '柚酢' (酢 means vinegar) became '柚子,' but that isn't certain. The Korean pronunciation is also written as '柚子' (pronounced yuja) in kanji, but due to the absence of a clear record the origin of the word is unknown.
Agriculture
Regarding domestic production regions in Japan, the villages of Umaji and Kitagawa in Kochi Prefecture, as well as the mountainous areas in the eastern region of the prefecture, are famous. There are also production regions throughout the nation, such as Masuho-cho in Yamanashi Prefecture, Motegi-machi in Tochigi Prefecture and the first production region, Moroyama-machi, in Saitama Prefecture. Overseas, it is cultivated on Chejudo Island, the southernmost island of the Republic of Korea, Kofun-gun in Gyeongsangnam-do Prefecture, and some parts of the People's Republic of China.
How to use
The juice of the yuzu citron is used in Japanese cuisine as a seasoning to add flavor and a sour taste. Not only is the fruit part used, but the pericarp is also used as a spice and condiment, such as by adding it to shichimi togarashi (a mixture of red cayenne pepper and other aromatic spices). Both green and ripened yuzu citrons are used. In the Kyushu region it's used as a seasoning called yuzu kosho, which is a spicy, hot Japanese condiment made from yuzu rind, chili and salt. It's made by mixing the pericarp of the yuzu citron with green chili when the pericarp is green and with red chili when it's ripened in yellow, and then salt is added and the result is either green or red in color.
The ripened yuzu citron still has a strong, sour taste, so it's usually not directly edible. As a suggestion to taste yuzu citron itself, not as a condiment, there is a recipe to confit it in sugar and honey by slicing the fruit into rounds with its pericarp intact. In Korea, there is a traditional tea called 'yuzu citron tea' (pronounced yujicha), which is made by diluting yuzu citron simmered like marmalade with hot water or water.
There is a beverage resembling lemonade, which is made by mixing squeezed yuzu citron juice with still water and sugar. The juice is used for chuhai (a shochu-based beverage), and there is a wine made from yuzu citron.
It has a uniquely fresh scent, so it's used in various perfumes. Recently, increasing numbers of domestic manufacturers have begun purifying the essential oil from plants in Japan, and they produce essential oil by compressing the pericarp. It's also used in many other ways.