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Fifty-six jujube cultivars were observed for their flowering habits and fruiting characteristics at Alcalde, New Mexico. Jujube cultivars were classified as morning blooming type or afternoon blooming type. Among the 56 cultivars observed, 24 belonged to the morning type and 32 belonged to the afternoon type. Eighteen out of the 56 cultivars had their blooming type reported for the first time. The sepal splitting for morning type occurred from sunrise to 1000HR, whereas it occurred between 1300 and 1600 HR for the afternoon type. Even though their opening time differed, pollen release happened during daytime for both—morning type released pollen in the afternoon and afternoon type released pollen in the late afternoon and the next morning. Rainy and cloudy weather delayed blooming for several hours. Each flower experienced the following stages during blooming: sepal splitting, sepal flat, petal standing, petal and anther separation, petal flat and anther standing, anther flat, and stigma browning; the time and duration of each stage varied with cultivar and blooming type. Flower size varied by cultivar and helps with cultivar identification. Cultivars Li, Li-2, Redland, Qiyuexian, Xiangzao, Teapot, and Daguazao were self-pollinating/self-fruitful in New Mexico. For open pollination, fruit set varied greatly by cultivar. ‘Abbeville’ had the best fruit set each year. Most cultivars had better fruit set from open pollination than selfpollination; however, self-fruitful cultivars Li, Li-2, and Redland had better fruit set with self-pollination than open pollination in some years. Open pollination increased fruit size for all cultivars. ‘Zhongning’, ‘Abbeville’, ‘Jinsi-2’, and ‘Globe’ had high seed percentage from open-pollinated fruit, whereas ‘Lang’, ‘Don Polenski’, ‘Junzao’, and ‘Xingguang’ did not produce fully developed seed in any years but some dark brown empty seedcoat sacs. Seed development was also affected by weather and pollination conditions. Fruit blooming type, pollen release, self-pollination, self-fruitfulness, selffertility, and seed development are all critical information for jujube breeders, researchers, extension personnel, and growers. Jujubes (Ziziphus jujuba Mill.), also called chinese dates, belong to the Rhamnaceae family. Jujube cultivars were first imported into the United States by U.S. Department of Agriculture (USDA) agricultural explorer Frank N. Meyer from 1908 to 1918 (Meyer, 1911; Thomas, 1924; Yao, 2013). In the past hundred years, jujubes were cultivated mainly in the southwest, southern, and southeastern states from North Carolina, South Carolina to Florida, and from Florida and Georgia all the way to California; but they had been reportedly grown as far north as Pennsylvania (Ashton, 2006, 2008; Atkins, 1987; Locke, 1948, 1955; Lyrene, 1979, 1983; Yao, 2013). Recently, we noticed some jujube trees along the historic Chinese railroads or mine worker campsites in the southwest (Yao, 2015). Dry jujubes were part of those Chinese workers’ diet and the littered seeds left behind grew voluntarily. Local people did not know much about jujubes but kept the trees that produced large and good-tasting fruit. These volunteer seedling plants belong to Z. jujuba and could be good germplasm for new cultivar selections. Early researchers had identified that jujube grew and produced well and had great potential in the southwestern United States (Fairchild, 1918; Hager and Edward, 1989; Lanham, 1926; Locke, 1948, 1955; Meyer, 1916; Sweet, 1985). Because of various reasons, however, jujube production is still limited. Recently, interest in jujubes from growers and consumers is surging, and nurseries have had a hard time meeting the market demand (Ron Ludekens, personal communication). The challenges now are very limited commercially available cultivars and research support. Growers are frustrated due to insufficient information on cultivars, cultural management, processing, and marketing. There are over 800 jujube cultivars known in China (Guo and Shan, 2010; Liu, 2008) while there are only a few cultivars commercially available in the United States with ‘Li’ and ‘Lang’ as the two most dominant. All jujube growers request more cultivars to extend the fruit supply season and to be used for different purposes to meet the consumers’ demand (Yao, 2013). Unlike apple or peach, jujube flowers are not initiated the previous year but the same year as they bloom. As the flexible deciduous fruiting structure—branchlets grow, they initiate flowers (Yao, 2012a). Jujubes have tiny flowers of 6 mm in diameter and have many more flowers than most fruit crops (Guo and Shan, 2010; Liu, 2006; Yao, 2012a). Each branchlet can have from 20 to over 100 flowers depending on the cultivar. Branchlet growth, flower initiation, blooming, fruit setting, and fruitlet growth occur simultaneously. Because of the high nutrient competition, jujubes, in general, have low fruit set (Guo and Shan, 2010). In the 1950s, the USDA Chico Plant Introduction Station had a jujube breeding program for some years; unfortunately, the Chico Station was closed in the late 1950s. During their jujube breeding/cultivar selection process, they mentioned the need for a complete understanding of flowering, pollination, selfsterility, and seed development and conducted some preliminary research on these topics (Ackerman, 1961). Yan et al. (2009, 2010) reported the fruiting characteristics of more than 100 Chinese cultivars. In the United States, the flowering and fruiting habits of existing cultivars and new importations are largely unknown, and this fundamental knowledge would be critical for jujube breeders and researchers. Extension personnel and growers also need this information for cultivar recommendations or cultivar selections. The NewMexico State University (NMSU) Sustainable Agriculture Science Center at Alcalde, New Mexico, has imported 30+ jujube cultivars from China and collected a number of cultivars in the United States for a total of over 50 cultivars. The objective of this study is to examine the blooming types, flowering characteristics, self-pollination/self-fertility, and seed development of these cultivars. Materials and Methods This experiment was conducted at the NMSU Sustainable Agriculture Science Center at Alcalde, NewMexico (lat. 36 05#27.94$ N, long. 106 03#24.56$W, and 1737 m elevation) and all cultivars used are listed in Table 1. Since trees were planted or grafted in different years, not all cultivars were used for every test in this study (cultivars used are clearly listed for each experiment). Among those cultivars, Abbeville, Lang, Li, Sihong, Received for publication 30 Jan. 2015. Accepted for publication 21 Apr. 2015. This project is partially supported by the USDA Specialty Crop Block Grant through the New Mexico Department of Agriculture. This project is also a contribution of the New Mexico Agricultural Experiment Station. We thank Rolston St. Hilaire, Richard Heerema, and Steve Guldan from New Mexico State University for their critical review of the manuscript. We also thank David Archuleta, David Salazar, Estevan Herrera, Margarito Hernandez, Bingye Xue, and Jenny Xue for technical assistance. We also like to extend our special thanks to Dr. G. Wang from Research Institute of Forestry, the Chinese Academy of Forestry, who collected the jujube cultivars in China for this project. To whom reprints should be addressed; e-mail yaos@nmsu.edu. HORTSCIENCE VOL. 50(6) JUNE 2015 839 Shuimen, Shanxi Li, Globe, Redland, Don Polenski, Fitzgerald, and So were planted in 2006, whereas ‘Jin’, ‘Sui’, and ‘Topeka’ were planted in 2011. Also in 2011, another 30 cultivars were imported from China as scionwood and grafted to wild jujube sucker rootstocks that had been planted in 2010. Because of the needs from researchers and growers and limited adult trees at Alcalde, New Mexico, we used young trees for part of the experiment. Another reason for using young trees is jujube’s precocity—they can bear fruit during grafting year or planting year. The planting density for the 2006 planting was 1.8 · 3.6 m, whereas the imported cultivars were grafted in the nursery area with spacing of 1.2 · 1.8 m. From 2012 to 2014, trees from both locations were used for the flowering habits and self-pollination/selffertility studies. Trees from a 2011 replicated planting with ‘Li’, ‘Lang’, ‘Sugarcane’, ‘Honeyjar’, ‘So’, ‘Shanxi Li’, ‘Li-2’, ‘September Late’, and ‘GA-866’ at 1.8 · 3.6 m spacing were also used for the self-pollination/self-fertility experiment. Trees were fertilized two to three times in lateMay to June each year at a rate of 33–45 kg N/ha and irrigated weekly depending on season and precipitation. Jujube flower number and blooming type. In 2012, 10 jujube branchlets (flexible deciduous fruiting branches) (Yao, 2012a) were sampled for 25 cultivars on 15 June. Total nodes and flower number at each node were counted and averaged for each cultivar. Flower diameter of 15 flowers for 46 cultivars was measured in 2012 and 2014. Jujube blooming times were observed at 3–4 dates in late June to early July each year for all cultivars from 2012 to 2014. At each date, the flower-blooming process was monitored hourly from 0600 to 1700 HR and at 2200, 0300, and 0500 HR. Four or five flowers per cultivar were harvested, stored in 1.5-mL tubes and brought back to the laboratory for pictures. The flower-blooming sequence was photographed hourly from 0600 to 1700 HR for ‘Li’, ‘Lang’, ‘Sugarcane’, ‘Sihong’, and ‘Abbeville’ in July 2013 with a Cole Parmer digital microscope (Vernon Hills, IL). Their pollen release, stigma changes, and nectar exudation were monitored during this process. Cultivar self-pollination/self-fertility study– bagging experiment. Four to ten 1to 3-yearold secondary branches of 40–45 cultivars were selected and half of them were randomly chosen for bagging on 6–7 June 2012, 8–10 June 2013, and 22–25 June 2014, whereas the other

Jujube (Ziziphus jujuba Mill.) Flowering and Fruiting in the Southwestern United States