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.
Twelve peach (Prunus persica) cultivars, six apricot (Prunus armeniaca) cultivars, two japanese plum (Prunus salicina) cultivars, three european plum (Prunus domestica) cultivars, four sweet cherry (Prunus avium) cultivars, and three tart cherry (Prunus cerasus) cultivars were monitored for winter damage at New Mexico State University's Sustainable Agriculture Science Center in Alcalde, NM (main site), and the Agricultural Science Center in Los Lunas, NM (minor site), in 2011. Uncharacteristically low temperatures on 1 Jan. and 3 Feb. were recorded as −7.2 and −11.3 °F, respectively, at Alcalde, and 4.8 and −13.9 °F, respectively, at Los Lunas. On 10 Jan. at Alcalde, live peach flower bud percentage varied by cultivar, ranging from 11% for Blazingstar to 25% for PF-1, and 85% to 87% for Encore and China Pearl. Apricot flower buds were hardier, with 70% survival for ‘Perfection’, 97% for ‘Sunglo’, and 99% for ‘Harglow’ on 10 Jan. By 10 Feb., almost all peach flower primordia were discolored, with no cultivar showing more than 1% survival. Based on this information, the 10% kill of flower buds for most peach cultivars occurred at temperatures equal to or slightly higher than −7.2 °F, and 90% kill occurred between −7.2 and −11.3 °F. On 10 Feb., 0% to 15% of apricot flower buds on spurs or shoots of the middle and lower canopy had survived. For vigorous shoots in the upper canopy, apricot flower buds on 1-year-old shoots had a higher blooming rate than those on spurs of 2-year-old or older wood. Flower buds of japanese plum were also severely damaged with less than 0.2% survival for ‘Santa Rosa’ and 4.8% for ‘Methley’, but european plum were relatively unaffected with over 98% flower bud survival for ‘Castleton’ and ‘NY6’, and 87% for ‘Stanley’ after −11.3 °F at Alcalde. Cherry—especially tart cherry—survived better than peach, apricot, and japanese plum after all winter freezes in 2011.
Jujube (Ziziphus jujuba Mill.) originated in China and grows well in a wide range of areas in the United States, especially the southwest. New Mexico State University’s Sustainable Agriculture Science Center has imported and collected over 50 jujube cultivars and conducted a series of jujube-related research projects. In this study, jujube phenology and pollen germination in New Mexico were investigated and two unique germplasm resources were reported. Jujubes leafed out 4–8 weeks later than most pome and stone fruits and bloomed 2–3 months later than apricots, peaches, and apples. It can avoid late frosts in most years in northern New Mexico and, thus, produce a crop more reliably than traditional fruit crops in the region. For the 48 cultivars tested for pollen germination, the germination rates ranged from 0% to 75% depending on the cultivar and year. ‘September Late’ had the highest pollen germination rate each year among all cultivars tested from 2012 to 2014, whereas ‘GA866’, ‘Maya’, and ‘Sherwood’ had the lowest. ‘Zaocuiwang’ was the first reported male-sterile jujube cultivar in the United States, and this character was consistent from year to year and, thus, it would be a valuable cultivar for jujube breeding. Cultivar Yu had pseudo-flowers which never bloomed or set fruit. It would be a useful germplasm as special landscape trees or for genomic study of jujube flowering-related genes.
Jujube or chinese date (Ziziphus jujuba) has fruit that is developed mainly from ovary plus some nectary disk tissue, and the fruit can appear smooth or bumpy on the surface. The objective of this study was to investigate the unique fruit development of ornamental ‘Teapot’ jujube. Unlike ‘Li’ and ‘Lang’, ‘Teapot’ jujube fruit had one to five protuberances on the shoulder of the fruit and few entirely lack protuberances. The stamens of ‘Teapot’ jujube flowers were fewer in number, misplaced in location, and deformed in shape—some stamens were anthers only while others were filament only. Deformed stamens of ‘Teapot’ jujube were always anchored in the nectary disk instead of at their normal location—near the edge of the nectary disk. After bloom, the residue of stamens, nectary disk, and ovary were all constituents of the developing fruit. The deformed stamens developed into the fleshy protuberances and equaled them in number. Fruit with only two protuberances predominated, which is how the ‘Teapot’ jujube acquired its name, but the ratio among protuberance categories varied between trees. With its unique and decorative fruit shape, and acceptable fruit quality, ‘Teapot’ jujube could be used as a backyard tree, both as an ornamental and for its fruit.
Shengrui Yao and Robert Heyduck
All jujube (Ziziphus jujuba) cultivars can be used as fruit trees and in landscaping, but there are four striking ornamental cultivars in our collection: Dragon, Mushroom, So, and Teapot. These cultivars are decorative and can be used for fruit, tree shape, or both as edible landscape plants. We evaluated these four ornamental jujube cultivars in central and northern New Mexico. All four cultivars grew and produced well but performed differently. ‘So’, imported from China in 1914, was a productive and contoured cultivar with medium-sized, sweet/tart fruit and bushy trees, with a decorative tree shape in winter. ‘Dragon’, a recent import from China, was the most dwarf cultivar tested, with small fruit and gnarled trees, and suitable for four-season ornamental use in landscapes. ‘Mushroom’, another recent import from China, had the most decorative fruit shape among the four cultivars tested, with vigorous and productive plants. ‘Teapot’, also a recent import from China, had irregular fruit shapes and vigorous and productive plants. All four cultivars were good edible landscape plants depending on customers’ preferences and space availability/limitation.
Shengrui Yao and Carl J. Rosen
Five primocane raspberry (Rubus idaeus) cultivars were evaluated in a high tunnel and in the field at Grand Rapids, MN, which is located in U.S. Department of Agriculture (USDA) plant hardiness zone 3b. Bare root plants of five cultivars (Autumn Bliss, Autumn Britten, Caroline, Joan J, and Polana) were planted in the high tunnel and in the field, each with a randomized complete block design at 2 × 5.2-ft spacing on 8 May and 14 May 2008, respectively. A propane heater was used periodically for frost protection in the high tunnel. All five cultivars overwintered well and primocanes emerged with minor or no winter damage in the high tunnel in 2009. The high tunnel extended the growing season for ≈4 weeks in both years. Raspberry plants in the high tunnel produced higher yield than those in the field, total 154 lb (6655 lb/acre) from the high tunnel vs. 0.5 lb (43 lb/acre) from the field in 2008 and 379 lb (16,378 lb/acre) vs. 80 lb (3457 lb/acre) in 2009. ‘Caroline’ and ‘Polana’ had higher yields than ‘Autumn Bliss’; ‘Joan J’ and ‘Autumn Britten’ yields were intermediate and not different from ‘Caroline’, ‘Polana’, or ‘Autumn Bliss’ yields. In terms of harvest date, ‘Polana’ was the earliest among the five cultivars tested, followed by ‘Autumn Britten’, ‘Autumn Bliss’, and ‘Joan J’. ‘Caroline’ was the latest. Essential nutrients in leaves for all cultivars both in the field and in the high tunnel were within sufficient ranges. Spider mites (Tetranychidae) and raspberry sawflies (Monophanoides geniculatus) were the major insect problems. In conclusion, primocane-fruiting raspberries can be successfully grown in high tunnels and produce substantially higher yields than in field plantations in northern Minnesota or areas with similar climatic conditions.
Shengrui Yao, Junxin Huang, and Robert Heyduck
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 self-pollination; 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, self-fertility, and seed development are all critical information for jujube breeders, researchers, extension personnel, and growers.
Shengrui Yao, Robert Heyduck, and Steven Guldan
Jujube (Ziziphus jujuba Mill.), also called chinese date, cultivars have not been formally trialed in the United States after the 1950s. Currently, there are five to six commercially available jujube cultivars, with ‘Li’ as the dominant one. Both growers and consumers demand a wider range of cultivars to extend the maturation season and for different uses. We tested jujube cultivars at three locations in New Mexico [U.S. Department of Agriculture (USDA) hardiness zones 6a, 7a, and 8a] to assess their adaption and performance. These are early performance results for fresh eating cultivars. Jujubes were precocious; 50% to 95% of trees produced during their planting year, depending on cultivar and location. The average yield per tree for trees in their second to fourth year after planting were 409 g, 4795 g, and 5318 g at Alcalde; and 456 g, 3098 g, and 5926 g at Los Lunas, respectively. The yields varied by cultivar and location. ‘Kongfucui’ (‘KFC’) was the most productive cultivar at Alcalde and Los Lunas in both 2017 and 2018, followed by ‘Daguazao’, ‘Gaga’, ‘Honeyjar’, Maya’, ‘Redland’, and ‘Sugarcane’. ‘GA866’, ‘Alcalde #1’, ‘Zaocuiwang’, and ‘Sandia’ had the lowest yields among the 15 cultivars tested. ‘Alcalde #1’ was the earliest to mature with large fruit, suitable for marginal regions with short growing seasons, whereas ‘Sandia’ had the best fruit quality among all cultivars tested, suitable for commercial growers and home gardeners. ‘Maya’, ‘Gaga’, ‘Honeyjar’, and ‘Russian 2’ were very productive, early-midseason cultivars with small fruit but excellent fruit quality—a perfect fit for the home gardener market. ‘Li’, ‘Daguazao’, ‘Redland’, and ‘Shanxi Li’ were productive with large fruit. Cultivars grew faster and produced higher yields, larger fruit, and higher soluble solids at more southerly locations. This article discusses cultivars’ early performance up to the fourth year after planting. This is the first jujube cultivar trial report in the United States since the 1950s.
Shengrui Yao, Robert Heyduck, Steven Guldan, and Govinda Sapkota
Jujube cultivars have been imported into the United States for more than 100 years, but cultivar trials have been limited. To accurately recommend cultivars for each region, trials have to be conducted. We have set up jujube cultivar trials at the New Mexico State University (NMSU) Alcalde (2015, USDA hardiness zone 6a), Los Lunas (2015, 7a), and Leyendecker (2017, 8a) Centers with over 35 cultivars at each site with two replicates and a complete random block design. We reported the early performance of fresh-eating cultivars in 2019. Here we report the performance of 19 drying and multipurpose jujube cultivars. Between 40% and 100% of jujube trees produced a few fruit to more than 100 fruit in the planting year, depending on cultivar and location. Trees were more upright at Los Lunas than at Alcalde. ‘Kongfucui’ (KFC) was the most productive cultivar at Alcalde with 13.3 kg/tree in 2019, followed by ‘Chaoyang’, ‘Jinkuiwang’ (JKW), ‘Pitless’, and ‘Lang’. The yield at Los Lunas was lower than Alcalde for the first 3 years after planting; however, ‘Jinsi 2’, ‘Jinsi 4’, ‘Jixin’, ‘Sherwood’, ‘Sihong’, and ‘Xiangzao’ produced higher yields at Los Lunas than Alcalde in 2019. All cultivars produced higher yields and contained higher soluble solids at Leyendecker than Alcalde and Los Lunas at similar ages. ‘JKW’ was the most vigorous and productive cultivar at Leyendecker. ‘JKW’, ‘Xiangzao’, and ‘Lang’ produced more than 3.0 kg/tree in their second year after planting. ‘JKW’ yielded 12.3 kg/tree in its third year after planting. Among the three locations, drying cultivars are not recommended for commercial production at Alcalde. However, home gardeners can plant multipurpose and early-drying cultivars at Alcalde. Leyendecker produced the best dry fruit with larger fruit size, rich color, and meaty fruit; dry fruit quality was acceptable in most years at Los Lunas except 2019. We preliminarily recommend some drying and multipurpose cultivars for each location. As trees mature and produce more fruit, we will fine-tune the cultivar recommendations. We also discuss the jujube cultivar zoning information in New Mexico and fruit uses.