Past, Present, and Future of Jujubes—Chinese Dates in the United States

This article summarizes jujube importation and culture history and current jujube cultivars in the United States. Described within are jujube taxonomy, biology, adaptation, fruit nutrition, pests and diseases, propagation, and research conducted in the United States. It also discusses the current issues with jujubes in the United States and possible solutions to them. Jujube adapted and grew well in the southern and southwestern United States, and it could become a valuable industry in the United States within 15 to 20 years. Jujube (Ziziphus jujuba Mill), also called chinese date, red date, or tsao (zao), is native to China (Liu, 2006; Qu, 1963). It originated in the middle and lower reaches of the Yellow River and has been cultivated in China for more than 4000 years (Guo and Shan, 2010; Liu, 2006). Botanically, it is derived from its wild relative sour jujube or wild jujube (Z. spinosa Hu). In ancient times, people selected and cultivated sour jujubes with big fruit and good flavor, and it gradually became the cultivated modern jujube species (Z. jujuba). There are still semicultivated sour jujubes like ‘Tiger Eye’, big round, sour jujube, and Yanjishan big sour jujube, which are popular in Beijing and Shandong Province, China, respectively (Guo and Shan, 2010). Jujube was first dispersed within China from its original center and then to countries bordering China. It was through the famous ‘‘Silk Road’’ that jujubes were introduced to Europe at the beginning of the Christian era (Liu, 2006; Lyrene, 1979). It is widely distributed in Persia, Armenia, Syria, Spain, and France (Locke, 1948; Lyrene, 1979). Most early jujube imported to Europe were seedlings (Locke, 1955; Lyrene, 1979) and were used as a table dessert or winter sweetmeat. Liu (2006) reviewed the jujube basics and research in China and worldwide. Lyrene (1979) briefly summarized the jujube tree situation in the United States. This review focuses on the cultivar history, biology, adaptation, and production challenges in the United States and makes a comparison with the jujube situation in China whenever necessary. Jujube History in the United States Robert Chisholm first brought jujube seedlings to the United States and planted them in Beaufort, NC, in 1837 (Rehder and Rixford, 1929). In 1876, G.P. Rixford brought jujubes from southern France to California’s Sonoma Valley and neighboring states (Rehder and Rixford, 1929). By 1901, jujube had escaped from cultivation and naturalized along the Gulf Coast from Alabama to Louisiana (Bonner and Rudolf, 1974; Lyrene, 1979). All of those early imports were seedling plants from Europe, not vegetatively propagated cultivars. It was not until 1908 that USDA agricultural explorer Frank N. Meyer introduced the first group of commercial jujube cultivars directly from China (Meyer, 1911). Meyer mentioned that one of the most promising tree crops of China was the chinese jujube, and he predicted jujube would be of great value in the semiarid south and southwest United States (Meyer, 1916). Jujube was one of two plants sculpted on the Frank N. Meyer Memorial Medal from the American Genetic Association in recognition of his contribution to plant germplasm collection and use (Fairchild, 1920). Jujube Cultivars in the United States The jujube cultivars in the United States now include several groups: Frank Meyer’s direct imports from China, U.S. cultivars from the USDA Chico jujube program, selections from across the United States, and recent imports from China or other jujubegrowing countries (Table 1). Those in Table 1 were listed as cultivars, but only a few of them were formally named, released, and went through cultivar trials. Cultivars imported through Frank Meyer and the remaining cultivars currently in the United States. Frank N. Meyer reportedly made four trips to China (1905–08, 1909–11, 1912–15, and 1916–18) (Plantexplorers.com, 2012). Locke (1948) mentioned that 83 of 2500 of Meyer’s PIs to the United States were jujubes. The author went through all the 1905–18 PI records (online now) and found that 67 jujube accessions were directly imported by Meyer from China (Table 2) (Galloway, USDA, 1907, 1908, 1909a, 1909b, 1912; Taylor, USDA, 1916a, 1916b, 1917a, 1917b, 1917c, 1922a, 1922b). Besides Frank Meyer’s collection, others also collected 20 jujube accessions from 1905 to 1918 with 14 from China, four from the United States, one from Paris, and one from Asia (Table 3) (Galloway, USDA, 1909c, 1910, 1911a, 1911b, 1911c, 1911d; Taylor, USDA, 1914a, 1914b, 1915, 1917a, 1917c, 1919). Later, those accessions were rarely mentioned in literatures. Table 2 indicates that Meyer visited the five major jujube-producing provinces in China: Hebei (formerly Chihli), Shandong, Shanxi, Shaanxi, and Henan Provinces as well as the Beijing and Tianjin areas. Frank Meyer collected roots or budwood of an unknown big-fruited cultivar during his first trip in 1905, which possibly did not survive because this was his first jujube import without any rootstock preparation, and the shipment itself may have been problematic. He sent back 12 batches of jujube seeds from jujube cultivars and sour jujube (Z. spinosa) from 1905 to 1907. Some of those seeds were collected in Sept. 1907 from famous cultivars like ‘Chin sze tsao’ (Jinsi zao in Chinese), ‘Yuen ling tsao’ (Yuanling zao), and two rare flat cultivars like mini apples in Shandong Province. In Mar. 1908, Meyer collected budwood for the famous ‘Lang’ and ‘Mu shing hong tsao’ together with ‘Hu ping tsao’ (Huping zao) and ‘Tsui ling tsao’ (Cuiling zao) from Shanxi Province. The USDA Chico Station received them in 20 Apr. 1908, which opened a new era for jujubes in the United States with big-fruited cultivars. Meyer collected the major cultivars in each region, like ‘Chin sze tsao’, ‘Yuen ling tsao’, ‘Lang tsao’, ‘Hu ping tsao’, and ‘Ta tsao’ (big-fruited tsao) and ‘Hsiao tsao’ (small-fruited tsao). However, ‘Ta tsao’ and ‘Hsiao tsao’ are different from region to region, which usually refer to the two local dominant cultivars, but they are different in size. He also collected some rare cultivars—a flat one resembling a mini apple, a seedless (pitless) one named ‘Wu hu tsao’ (Meyer, 1911), ‘Yu tsao’ (Ya zao, tooth-shaped), a contoured one with gnarled and zigzagged branches, ‘So’ (PI 37484), and another one with crooked and twisted branches called Received for publication 1 Mar. 2013. Accepted for publication 2 Apr. 2013. This paper is partially supported by the USDA Specialty Crop Block Grant through the New Mexico Department of Agriculture. This is also a contribution of the New Mexico Agricultural Experiment Station, New Mexico State University, Las Cruces, NM. I thank Steve Guldan, Richard Heerema, and Geno Picchioni from New Mexico State University for their critical review of the manuscript. I also thank Martha Davis from Los Alamos, NM, and Roger Meyer from Fountain Valley, CA, for their comments and suggestions. To whom reprint requests should be addressed; e-mail [email protected]. 672 HORTSCIENCE VOL. 48(6) JUNE 2013 ‘Dragon’ or ‘Dragon’s-claw’ (Meyer, 1911). He also intentionally collected wild jujube seeds as rootstocks (Meyer, 1911) and seeds from trees with good fruit flavor for cultivar breeding purposes (Table 2). Meyer mentioned several times the hen egg-sized jujube fruit, and ‘Li’ was one of them. Of the 67 accessions imported, the very first one (PI 17752) was an unknown cultivar, 35 were vegetative parts from 34 cultivars (two ‘Wu hu tsao’ from different locations), one accession was a rooted plant from one of those 34 cultivars, and another one was a sample of dried fruit; the other 29 accessions were seeds from either Z. spinosa (three accessions) or Z. jujuba cultivars (26 accessions). All of Frank Meyer’s introductions were first planted at the USDA Plant Introduction Station at Chico and were later distributed to other USDA stations, especially in Dalhart, Big Spring, and Lubbock, TX; Woodard and Lawton, OK; Garden City, KS; and Tucumcari, NM (Locke, 1948). In the mid-1930s, J.L. Collins of the Tennessee Valley Authority tested 40 cultivars near Norris, TN, and ‘R3T1’ (Row 3, Tree 1) was a selection from that planting (Osborn and Miller, 2009). In the 1920s, the USDA Chico Station recommended four cultivars—‘Mu shing hong’ (PI 22684), ‘Lang’ (PI 22686), ‘Shui men’ (PI 38245), and ‘Li’ (PI 38249) (Thomas, 1927). ‘Mu shing hong’ was described as ‘‘one of the best varieties’’; ‘Lang’ was ‘‘the best variety for general purposes’’; ‘Shui men’ was ‘‘of average size and useful for many purposes’’; and ‘Li’ had ‘‘the largest fruit and is one of the best to eat fresh and ripened one to two weeks later.’’ Coincidently, all four cultivars were originally imported from Shanxi Province. Locke (1948) mentioned three of the four cultivars without ‘Mu shing hong’. The observation and research work on jujubes at the USDA Chico Station continued until the end of the 1950s (Ackerman, 1961). Now ‘Li’ and ‘Lang’ are the two most available cultivars in the United States. ‘So’, ‘Yu’, ‘Mu’ (Mu shing hong), and ‘Shui men’ of Frank Meyer’s importation are also available in small quantities at Fountain Valley, CA, a private collection of Roger Meyer (not directly related to Frank Meyer), who is a jujube enthusiast and vice-president of California Rare Fruit Growers [Xotcfruit (R. Meyer), 2013]. Cultivars from the USDA Chico breeding program. There were several cultivars bred at the USDA Chico Station by Dr. Ackerman and his colleagues, although most of them were not officially released. ‘Chico’, also called ‘GI-7-62’, bred at the USDA Chico Station, is a seedling of PI 37484 (‘So’) with round but flattened fruit. Paul H. Thomson, who is one of two founders of California Rare Fruit Growers, named it ‘Chico’ to remember the Chico Station in California (Thomson, 1971). ‘GI-1183’ is another cultivar from the USDA Chico Station bred by Ackerman from unknown sources (Ashton, 2006). ‘GA866’ is a cultivar bred and selected at the USDA Chico Station by Ackerman with unknown sources (Ashton, 2006; California Rare Fruit Growers, 1996). ‘Thornless’ is a cultivar bred/selected at the USDA Chico Station by Ackerman and Smith; the fruit shape is similar to ‘Lang’ and the source is unknown (Ashton, 2006). Cultivar/selections from across the United States. The United States does not have large germplasm resources (gene pool) for cultivar selection like China does, but after more than 175 years of jujube cultivation in the United States, there are some jujube plants with great fruit quality scattered in people’s backyards without names. Locke (1948) mentioned that the patent office distributed jujube seeds to interested people in 1854. This is why there are many cultivars from different states named after people or towns, which are the result of long-term selections from seedlings or survivors of Frank Meyer’s imports. Some of them could be the same cultivar but were found and renamed at other locations. Genetic analyses are needed to clarify their relationships. To date, there has not been much genetic or molecular work on jujubes for cultivar classification and grouping in the United States. Some cultivars from this group are of sufficiently high quality to be officially named, but most of them lack regional tests. For example, ‘Sherwood’ (Atkins, 1987) was an excellent cultivar for California, Texas, and Louisiana, but it has poor fruit set and does not ripen before first frost in northern New Mexico. The author noticed several jujube trees 30 to 50 years old or older across New Mexico with good quality for both fresh eating and drying that would be worth further attention and testing. Recent imports from China and other jujube-growing areas. In California, Roger Meyer imported several cultivars from China’s Nanjing Botanical Garden in the 1990s [Xotcfruit (R. Meyer), 2013]. Jim Gilbert of One Green World Nursery in Oregon, introduced ‘Autumn Beauty’ and ‘Winter Delight’ from China (Ashton, 2006) and several cultivars from the Ukraine (personal communication) and the New Mexico State University Sustainable Agriculture Science Center at Alcalde, NM, directly imported over 30 cultivars from China in 2011. Cultivar evaluation trials are greatly needed across the United States to move jujube production forward. Growers need more cultivars for different purposes and to extend their harvest seasons. The jujube cultivars in China have changed and increased rapidly after 1980 and especially since the 1990s. Researchers have done significant work on jujube germplasm collection and selections. An increasing number of new selections were named after 1990, but hybridization breeding is still problematic as a result of jujube’s tiny flower and the multiple flowers in a florescence (Liu, 2006). There are over 800 jujube cultivars in China now (Guo and Shan, 2010). There are total of 60 to 70 ‘‘cultivars’’ in the United States, but only a few of them are commercially available. Hopefully, after several years of research and evaluation, we will be able to recommend 10 to 20 cultivars for different purposes to growers. Taxonomy and Biology Jujube belongs to the Rhamnaceae (Buckthorn) family. Its close relative is the sour jujube, from which cultivated jujubes were selected (Liu, 2006). Sour jujube grows in the wild in the mountainous areas of northern China. It is sometimes used as hedgerows, Table 1. Current jujube cultivars in the United States.