Native Range and Climate

The native range of Ziziphus jujuba is unknown due to extensive cultivation throughout Eurasia, but it is believed to be somewhere between the eastern tip of the Mediterranean Basin and China.

Jujubes are extremely drought and heat tolerant once established, but irrigation during bloom appears to help improve their (often poor) fruit set.  This has been observed in not just hot and dry climates, but in the humid subtropical (Cfa) climate as well.  However, older trees, as well as varieties that produce smaller fruit, may not require as much or any supplemental irrigation, since both factors seem to help prevent fruit drop.  Additionally, gibberellic acid (ga3), or a borax solution, sprayed during bloom may also help increase fruit set.^[1]

In regions between the two environmental extremes, jujubes often perform very well without supplemental irrigation, although frequent watering can improve fruit quality.  In very hot climates, irrigation will help prevent the fruit from drying out before they fully develop, and in wet climates, exposure to sunlight throughout the day can be very important for fruit set, especially when the tree is quite young.  Furthermore, if the grow season is long enough, some varieties may produce two crops, but in hot desert climates, the first crop may be of poor quality due to extreme heat.

Flowers and Blooming-type

Jujubes bloom for a very long time, 6 weeks or more on current year's growth, but each flower only produces pollen and nectar for a day or less, depending on their blooming-type.^[2] The stigma becomes receptive a few hours after pollen and nectar start to produce,^[2] but it is unclear as to how long this lasts.  In New Mexico, jujube flowers were between 5mm to 7mm in diameter, depending on the variety,^[2] and each variety produced a fairly consistent number of flowers at each node, depending on the section of the branch.  Those near the beginning and end generally had less flowers.^[2]

Jujubes can either be a morning blooming-type (AM) or an afternoon blooming-type (PM).^[2] While the former opens their flowers in the morning, the pollen is primarily released in the afternoon, and it continues (along with nectar production) until the end of the day.  The afternoon blooming-type releases pollen in the late afternoon as well as the next morning.  However, rain or cloudy weather can delay this process for a few hours.^[2]

NOTE: Jujube varietal traits, such as the shape and size of the fruit, may vary – to some extent – based on the year, location, and, perhaps, the age of the tree.  Information on flower size and their average number per node is based entirely on data from New Mexico at this time, and the "early section" that is shown within the information provided for some varieties is based on the first two nodes of each flowering branch.

Mislabeling

In the US, some varieties have a reputation for regularly being mislabeled.  For example, there may be more than one contorted variety labeled 'So', and 'Autumn Beauty' (an early ripening variety) was once, and may still be, regularly sold under the name 'Winter Delight' (a late ripening variety) by at least one or two major nurseries.  Silverhill and Tigertooth are often considered to be the same variety, but they may have slight differences.

Pests and Disease

There are no significant pests or diseases that affect jujubes in the United States.  In Asia, jujube witch's broom is considered to be the most destructive, often killing the tree 3 to 5 years after infection, but a number of resistant varieties have been identified and are being used in breeding programs.^[3] Alternatively, trunk injections of various antibiotic combinations have been used to cure infected trees with a high rate of success.^[3] Other diseases that can cause significant damage to the crop include leaf-rust^[4], fruit shrink disease, and fruit rots.  However, many appear to be highly resistant to fruit shrink disease.^[5]

Additional Notes

Jujube trees are generally thorny, but they become less so as they age.  They are also known to sucker profusely.