The History of Satsuma
By: The Citrus Industry, Volume I
Chapter 4, Horticultural Varieties of Citrus
Robert Willard Hodgson
This mandarin is the famous and highly important Unshû mikan (Unshiu) of Japan. The name satsuma, by which it has become known in the Occident, is credited to the wife of a United States minister to Japan, General Van Valkenberg, who sent trees of it home in 1878. Satsuma is the name of a former province, now Kagoshima Prefecture, on the southern tip of Kyushu Island, where it is believed to have originated. This mandarin may be described as follows:
Fruit medium-small to medium, oblate to subglobose; sometimes slightly necked; seedless. Orange-colored but commonly matures prior to development of good color. Areole faint or indistinct and small; navel frequently present. Rind thin, somewhat leathery; surface moderately smooth and with large and prominent oil glands; easily separable. As the fruit passes through maturity, rind surface becomes increasingly bumpy and likewise its separation increases somewhat. Segments 10 to 12, with tough carpellary membranes, loosely separable; axis hollow. Flesh orange-colored; tender and melting; flavor rich but subacid. Pulp-vesicles short and broad. Season of maturity very early to medium early (includes the earliest-known mandarin varieties). Fruit holds poorly on trees after maturity and must be picked promptly, but stores well. The occasional seeds found have light green cotyledons.
Tree slow-growing, small to medium-small, usually spreading and drooping, nearly thornless; foliage open. Leaves dark green, large, long, lanceolate, and tapering at base and apex, the latter usually taper-pointed. Both main and primary lateral veins prominent above as well as below. Petiole slender, very long, and wing-margined. Tree very hardy to cold and resistant to unfavorable conditions.
The highly distinctive satsuma mandarin is considered to have originated in Japan sometime prior to 1600 A.D., the approximate period of the earliest known reference to it. Since it has never been found in China and its Japanese name Unshû is considered to be a corruption of Wenchow, an ancient province of China, it seems likely that it originated as a chance seedling from a fruit or form imported from that country, probably from Wenchow Province. According to Ziegler and Wolfe (1961), the first recorded introduction into the United States (Florida) was by George R. Hall in 1876. The satsuma reached California not long thereafter and within a few decades was established in collections in the Mediterranean basin and elsewhere.
The satsuma mandarin tree is the most cold-tolerant of citrus fruits of commercial importance, mature dormant trees having survived minimum temperatures of 15º F to 18º F in northern California and southern Alabama without serious injury. Moreover, because of its apparent low total heat requirement, some varieties ripen earlier than any of the oranges or other mandarins. However, warm weather is required during the growing season for the development of satisfactory quality. As a consequence, the satsuma is adapted to regions of winters too cold for other citrus fruits and with growing seasons sufficiently warm to produce fruit of early maturity and good quality. For reasons that remain obscure, this mandarin has not proven commercially successful in the milder and hotter portions of the subtropics or in the tropics. Its range of climatic adaptation for commercial culture is therefore narrow and restricted to the upper and colder portions of the subtropical zones.
In the United States, climatic conditions suitable for satsuma mandarin culture occur in parts of northwestern Florida, in a narrow strip extending along the Gulf of Mexico across Alabama, Mississippi, and Louisiana into eastern Texas, and in the thermal belt of the Sacramento-San Joaquin Valley basin of California. Some decades ago, there existed in the Gulf Coast region what appeared to be a thriving and promising young industry of some thousands of acres. Primarily because of a series of unprecedented vicissitudes—introduction of the citrus canker disease and necessity for its eradication and recurrent devastating freezes—those plantings have virtually disappeared. Replacements currently comprise only a fraction of the original acreage. At about the same time, small plantings were made in the Sacramento Valley of California which persisted for several decades but ultimately were removed or largely replaced with other varieties, primarily because of handling and marketing difficulties and possibly rootstock-scion incompatibility problems involving virus diseases. In recent years, however, there has been a revival of interest in this mandarin and about 1,500 acres have been planted, principally in the San Joaquin Valley.
In portions of southern Japan, climatic conditions are favorable to the production of early ripening satsuma mandarins of high quality and maximum size, which has permitted the development of the world's largest and most important mandarin industry. The total planting in Japan for 1963 was reported to be 215,000 acres with a production of about 28 million 70-lb box equivalents. The areas of production are widely distributed, involving the islands of Honshu, Shikoku, and Kyushu and nineteen prefectures (chap. 2, table 2-69, p. 142 [text version, Revised Ed.]). At the present time, satsuma mandarins comprise about 80 per cent of the citrus acreage and account for approximately a third of the total fruit tonnage harvested in Japan.
While this fruit is grown primarily for fresh consumption, a significant and increasing portion of the crop is canned as fruit segments or juice. Limited quantities of fresh fruit have been exported to Canada, where they have comprised the earliest new-crop citrus fruits to reach the markets. Export of canned fruit segments has increased greatly in recent years and this excellent product is now found in both American and European markets.
The most unusual or distinctive features of the Japanese industry are as follows: (1) much the greater part of the orchards are close-planted and are situated on relatively steep, bench-terraced slopes; (2) the rootstocks used are trifoliate orange (Poncirus trifoliata [L.] Raf.) and Yuzu (C. junos Siebold), mainly the former; (3) a common and recommended practice is inarching trees on trifoliate rootstock at 12 to 15 years of age or even older with Yuzu seedlings to offset dwarfing and prolong their productive life; (4) the employment of regular and severe pruning; and (5) the availability of extensive storage facilities which make possible notable extension of the fresh-fruit marketing and processing seasons.
At the dawn of modern horticulture in Japan, five kinds, groups, or varieties of unshu mikans were recognized, three of the names of which refer to localities or districts, one to season of maturity of the fruit, and the other to antiquity of origin. These horticultural groups are as follows:
1. Wase (Early)—All early-ripening clones were placed in this group irrespective of origin, known or otherwise. Indeed, all varieties of Unshû are classified into two groups—Wase Unshû (earliest to ripen, hence very early) and Unshû (ripening later, but still early). More recently the latter has been subdivided into the intermediate or midseason varieties—Nakate Unshû—and the late ripening varieties—Futsu Unshû. Wase itself is therefore not a horticultural variety but constitutes a group of very early ripening varieties, each of which carries its own name. In general, however, these varieties are distinctively different from the typical Unshû.
2. Zairai (Native, indigenous, or old)—This group is said to include what are considered to be the oldest clones of unknown parentage or origin. Thus, Miyagawa, currently the most important of the Wase varieties, is known to have originated as a limb sport in a Zairai tree. Zairai does not exist as a named variety, however, though Zairai clones as a group are usually seedy and inferior in other respects. They are reported to have originated mainly in Fukuoka Prefecture of Kyushu Island where the Unshû was early taken from Satsuma Province.
3. Owari (an old province on Honshu Island, now Aichi Prefecture)—This group, much the most important, represents an old clonal variety which early became popular and predominant in Owari Province and may have originated there, although it is thought to have come from Ikiriki of Nagasaki Prefecture. Because of its excellence, it spread throughout the country and until approximately 1940 was virtually the only variety planted commercially. Since World War II, however, the plantings have been restricted largely to derivative varieties known to have originated as bud mutations in Owari trees. Owari itself seems no longer to be propagated as a clonal variety, though it still comprises the bulk of the production. As a group it is characterized by good tree vigor and productivity and flat fruit of good quality which, because of the firm consistency of the flesh and tough carpellary membranes, is especially suitable for canning.
4 and 5. Ikeda and Ikiriki (town or village names in Osaka and Nagasaki Prefectures)—These groups seem also to represent old varieties of local origin no longer propagated, though old plantings still exist—of the former, on Shikoku Island and in nearby Wakayama Prefecture on Honshu Island; of the latter, mainly in Saga and Nagasaki Prefectures of Honshu Island.
Ikeda is reported to be characterized by small, subglobose, and virtually seedless fruit of mediocre quality and relatively late maturity. The trees of Ikiriki are said to be small, compact, and not very productive, but the fruit is reported to be seedless and of excellent quality.
During the period of 1908-1911, approximately a million satsuma trees were imported and planted in the United States. A few years later, a study of the varieties included in the importations (Scott, 1918; Tanaka, 1918) disclosed that they consisted mainly of the Owari type or variety, although three others—Wase, Ikeda, and Zairai—were also identified and described. In view of these facts, the authenticity of the Wase and Zairai clones in question is doubtful at least and the clones of Owari and Ikeda should probably be regarded as selections of those varieties. Fortunately, however, the Owari identified and propagated in the United States appears to be true to type for Silverhill, a seedling clone derived from it in Florida and considered to be of nucellar origin. It has been tested in Japan and is among the clones currently recommended for planting there.
The satsuma mandarins must be regarded as a highly unstable group, for as early as 1932 Tanaka (1932) reported numerous bud variations of which some thirty were named and described. This list has now been extended to a hundred or more, some of which appear to be identical although of different origin.