Jujube is native to China, particularly the more arid areas. It has been cultivated there for millennia, with annual production currently exceeding 1.5MT. Other countries worldwide now contribute to global production but in much smaller quantities.
It has a very low chilling requirement for flowering and favours a sub-tropical environment. Ideal mean temperatures range from 5-22°C. Mature trees are extremely drought tolerant (as low as 200mm pa) but will also withstand rainfall up to 2000mm pa providing soil is well-drained. Mature trees in dormancy are known to have survived winter cold of -38°C.
It is a small deciduous spiny tree possibly growing to a height of 15m with a very deep root system and an unusual zigzagged branch shape. There are no truly spineless cultivars. The upper side of leaves is dark, glossy green with three longitudinal veins. Trees have been known to produce fruit for centuries.
Rhamnaceae Family. There are about 170 species of Ziziphus but the only other one valued equivalently for its fruit is Indian jujube or Ber, Z. mauritiania. Indian jujube is even more thorny and prone to massive suckering, and is a declared weed in many parts of Australia including WA.
Grows in a very wide range of soils with pH 4.5-8.5. Water and nutrient needs benefit from a mycorrhizal association.
Seeds should preferably be used only to provide rootstock material for grafting superior cultivars as otherwise productivity is highly variable. The plant can sucker profusely and these are the easiest and main source of rootstocks. Standard grafting techniques present no major problems but cuttings have not been very successful. Most new cultivars have been the result of opportunistic selection; cross-breeding is difficult.
The most common cultivars grown in Australia are Chico (apple-shaped), Li (round-shaped) and Lang (pear-shaped). Chico is the best performer in WA.
Inflorescences are cymes and borne in the leaf axils of the small deciduous bearing shoots in spring. Flowers are perfect, but dichogamous behaviour means that most require cross-pollination. In addition, a few jujube cultivars are triploid, further complicating pollination and fruit set. The yellow flowers are fragrant and attractive to many species of insects that effect pollination. However, pollen viability in most cvs is less than 50%, and fruit set is typically less than 1%.
The plants require full sun and regular fertilizer applications for heavy fruiting.
This is best during dormancy. Normal flowering and fruit set is affected with strong winds.
Suckers should be removed otherwise a thicket of trees can eventuate. They can be trained as a bush with several main lateral branches or a small tree. Maintaining height to a maximum of 3-5m is relatively straightforward.
It is a drupe, varying in size and shape depending on cultivar and management. There may be 0-2 seeds.
Juvenility lasts for 3-8 years. Thereafter the staggered fruiting period is usually extended throughout summer/early autumn, and fruit can be usefully stored in a refrigerator crisper for more than 2 weeks.
It is usually eaten fresh, dried, candied, smoked or pickled. The edible low-acid flesh contains more than 20% carbohydrates and is a good source of calcium, iron and vitamin C if not dried.
It is a very hardy plant, usually trouble free if in good health. Fruit flies, and the phytoplasma Witches Broom can cause problems. Disease risk increases in very humid environments.
This species is almost designed for our climate, being able to withstand our ferociously hot dry summers. If a good cultivar is selected and managed well it will produce prolifically, with reports of many thousands of fruits carried on mature trees. Downsides are the spines and suckering.