Beni Yuzu, Kansu, Kanzu, Mukaku-yuzu, To Yuzu, Toko Yuzu (sec. Cottin 2002)
Citrus x junos Siebold ex Tanaka, pro sp. (sensu Tanaka sec. Cottin 2002; sensu Bayer et al. 2009); Citrus reticulata Blanco var. austera Swingle ? x Citrus ichangensis Swingle (sensu Swingle and Reece 1967)
Swingle and Reece (1967) noted that:
"This well-known citrus fruit tree of China and Japan is doubtless another ichandarin resulting from an accidental cross-pollination of some cultivated variety of the mandarin orange by the Ichang papeda, probably accomplished by some insect. The Yuzu is unlike either parent species in many important taxonomic characters; however, there has been little opportunity to learn its characters or experiment with it since one parent, C. ichangensis, is a wild species (apparently never cultivated in China) that was not discovered until 1913. The hybrid nature of the Yuzu was not known even in the Orient, where C. ichangensis is a botanical curiosity....hybrids that show astonishing similarity to the Yuzu have now been produced in this country between the Ichang papeda and the satsuma orange (a form of C. reticulata )."
"The Yuzu, which shows many points of similarity with C. ichangensis, is doubtless another of these hybrids; it has been known in China since ancient times and is widely grown both in northern China and in Japan."
"Meyer, in October, 1914, found this hardy citrus fruit tree in northwestern China, in the latitude of Atlanta, Georgia, at Hsi-Chi village, near Siku (Lat. 33° 44' N., Long. 104° 30' E.), in the southern part of Kansu Province. It was growing at an altitude of 610 to 1,372 meters (2,000 to 4,500 ft.) along with walnuts, persimmons, pomegranates, and the Trachycarpus palm. Meyer (1918) described the fruit as follows: "The fruits were loose-skinned, round flattened, the size of mandarin oranges, color of rind light yellow; rind full of oil glands, smelling like a fine lemon; segments separating easily; fairly juicy and of an agreeable sharp sour taste; contains plenty of large seeds." Meyer's photograph, taken at His-Chi, Kansu Province, was published by Tanaka (1922, pl. facing p. 243).
Two strains of this hybrid grown in north-central China were described by Hu (1934, pp. 47-48). They are: (1) hsiang ch'êng (aromatic ch'êng), a name current in Chekiang and Kiangsu provinces; and (2) Lo han ch'êng (Buddhist disciple Ch'êng), a name used in T'ang-ch'i, Chekiang Province. Hu (1930) has shown the first in his figures 34 and 35 and the second in figures 36 and 37.
Tanaka has directed attention (1933) to certain Chinese records which seem to prove that this plant was known and cultivated in ancient China under the name yu. This name is still used for it in Japan but not in China, where the name is now applied to the pummelo (C. grandis), a very different species having much larger fruits with agreeably flavored sweet pulp. The Yuzu is now called ch'êng tzu in China and was so called as early as 1108 A.D. by Tang Shên-wei in his great illustrated herbal, the Chêng lei pên ts'ao, published in that year.
In the "Spring and Summer Annals" of Lü Pu-wei, who died in 237 B.C., the yu of that epoch was described as follows (as translated by Michael J. Hagerty): "Some are sweet and some are sour. The sour are called hu kan or Barbarian sweet. At present the common people sometimes speak of the ch'êng as yu but this is wrong." This last sentence proves, as noted by Hagerty, that there were already in the third century B.C. two different fruits called yu. It seems probable that the Japanese name yuzu, which corresponds to yu tzu in the Chinese spoken language, has been kept with its ancient meaning in Japan, but that the meaning has for many centuries been lost in China.
The Yuzu was named Citrus junos (as a good species) by Tanaka, but, as has been shown above, it is very probably a hybrid of the Ichang papeda and some Chinese cultivated variety of the mandarin orange and therefore cannot be recognized as a good botanical species."
"The Yuzu, a hardy variety widely grown in Japan and sparingly in northern China as a substitute for the lemon, has been considered by some to be a good natural species of Citrus. However, it is now found to be a hybrid of a recently discovered Chinese species of Citrus (C. ichangensis) probably with a sour mandarin (C. reticulata var. austera). A hybrid of similar parentage made in the United States is astonishingly like the Yuzu."
Crown compact or dense, not weeping. First year twig surface glabrous; second or third year twig surface striate; thorns straight; prickles absent or not persistent. Petiole glabrous, length medium or very long, wings wide, adjoining the blade or tucking beneath blade. Leaflets one, margin entire or bluntly toothed, shade leaflet blades flat or weakly conduplicate, sun leaflet blades strongly conduplicate. Leaflets spicy or peppery when crushed. Fruit as broad as long or longer than broad, rind green-yellow (6), yellow (7-10), yellow-orange (11) or orange (12), rind texture medium rough (6-7), firmness leathery, navel absent, flesh yellow, taste sour.
Swingle and Reece (1967) provided the following additional notes on the species:
"The Yuzu is a medium-sized spiny tree; leaves lanceolate-acuminate, with rounded bases but with pointed, usually acuminate tips, slightly crenulate-margined toward the tips, leaf blades 5-7 X 2.5 X 3.5 cm; winged petioles obovate, 18-30 X 6-15 mm, with entire or very faintly crenulate margins; fruits depressed-globose, usually with 10 locules, 5-7 cm diam., 4.5-5.5 cm high, with a rough, bumpy peel, greenish in color when ripe; pulp very acid, and somewhat bitterish; seeds plump, about 12-14 X 7-8 X 6-7 mm."
Swingle and Reece (1967) additionally noted that: "The Yuzu is sparingly cultivated in north-central China, in Kiangsu, Chekiang, Hupeh, and Kansu provinces, and in the plateau regions of southwestern China and as far south as Yunnan Province. It is more commonly grown in Japan, both for its acid fruits, which are used as a substitute for lemons or limes, and as a rootstock for the satsuma and other cultivated varieties of citrus fruits."
Bayer, R.J., D.J. Mabberley, C. Morton, C.H. Miller, I.K. Sharma, B.E. Pfeil, S. Rich, R. Hitchcock, and S. Sykes. 2009. A molecular phylogeny of the orange subfamily (Rutaceae: Aurantioideae) using nine cpDNA sequences. American Journal of Botany 96: 668–685.
Cottin, R. 2002. Citrus of the World: A citrus directory. Version 2.0. France: SRA INRA-CIRAD.
Hu, C.C. 1930. Citrus survey in China (First Report). Nogyo Oyobi Engei 5: 1461–1476, 1624–1649.
Hu, C.C. 1934. The history and distribution of citrus fruit China. Journal of the Agricultural Association of China, Numbers 126–127: 1–79. (Reprinted as : Bulletin, University of Nanking, College of Agriculture and Forestry 31: 79.)
Meyer, F.N. 1918. No. 39897—Citrus sp. U.S. Department of Agriculture Bureau of Plant Industry Inventory of Seeds and Plants Imported No. 42: 33–34.
Nagai, K. and I. Takahashi. 1925. Root grafting of the citrus tree. Research Bulletin, Imperial Horticultural Experimental Station [Okitsu, Japan] 3. 11 pp.
Swingle, W.T. and P.C. Reece. 1967. The botany of Citrus and its wild relatives. In: Reuther, W., H.J. Webber, and L.D. Batchelor (eds.). The Citrus industry. Ed. 2. Vol. I. University of California, Riverside. http://lib.ucr.edu/agnic/webber/Vol1/Chapter3.html.
Tanaka, T. 1922. Citrus fruits of Japan; with notes on their history and the origin of varieties through bud variation. Journal of Heredity 13: 243–253.
Tanaka, T. 1933. Kankitsu no kenkyû. (Citrus studies.). Yokendo Shoten, Tokyo. 463 pp.
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Additional information on this cultivar at University of California: Riverside Citrus Variety Collection
1GRIN: Germplasm Resources Information Network; NPGS: National Plant Germplasm System
Citrus ID Edition 2
October, 2011
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