The Jujube: Ziziphus jujuba
Introduction
Cultivars of Ziziphus jujuba (Syns. Z. sativa. Z. vulgaris)
— jujube, Chinese jujube, red date or Chinese date — have
long been grown for their excellent dessert fruits. Native to temperate
Asia, where there are many cultivars grown for fruit, jujube has become
naturalised in many other warm temperate and subtropical regions;
jujube plants were brought from Syria to the Mediterranean in ancient
Roman times. In China it is considered one of the five principal fruits.
Description
The
jujube is a deciduous shrub or tree growing to 9 m high and 7 m (wide
with drooping branches, flexuous twigs, and pairs of short curved and
occasionally long spines. The jujube is unusual in that it sheds many
of the short lateral-bearing twigs — ie it has deciduous branches
as well as leaves. This branchlet loss gives the tree a distinctive
zig-zag appearance in winter. Trees often send up suckers many feet
from the mother plant. As the growing season commences, each node of a
woody branch produces 1-10 branchlets, most of which are deciduous and
fall in the autumn. Leaves are 2.5-6 cm long, elliptic, leathery,
shiny, on short stalks.
Flowers are small and yellow, about 5 mm
across, in axillary clusters of 2-3 on the current season's growth from
the small lateral branchlets. They appear in late spring or summer,
depending on the climate; flowering can continue over an extended
period, although each flower is receptive to pollen for a day only.
Pollination is via insects, including bees; although trees are usually
self-fertile, fruits are bigger and more numerous with cross
pollination. Fruits are between a cherry and a plum in size, 1.5-4 cm
long, roundish-egg shaped like small plums (sometimes round or
pear-shaped). The amount of flesh is very variable between selections.
The skin is bright green and shiny when the fruit is mature — at
this stage the flesh is crisp, sweet, with an apple flavour; if left on
the tree, the skin begins to brown in a few spots, the brown areas
coalesce to completely cover the surface, then the fruit begins to dry
and wrinkle; by the time it is fully ripe the jujube is a rich
red-bronze and most resembles a prune or dry date — hence the
name Chinese date. The texture now is chewy and resembling a date, and
the taste has improved.
The fruits contain a single, hard-shelled stone which encloses one or two seeds.
Under natural conditions, Z. jujuba
forms a deep and substantial taproot, making it drought tolerant. The
tree is winter hardy to zone 6, -20 °C, but shoots may get cut back
by less severe frosts than this if not properly ripened. It has a short
chilling requirement and tolerates extreme heat, 40 °C or more.
Uses
The
fruits have a pleasant acid taste when fresh, but are usually allowed
to dry on the tree, when they are chewy and more palatable. The rough
and sharp-pointed seed shell is not very suitable for young children.
They are used as a substitute for dates and used in savoury dishes
— rice, fish, soup — and in cakes. In Asia they are
sometimes ground into flour and used for bread; they can be added to
bread mixes. The fresh fruit pulp contains about 9% sugars, 1.7%
pectin, 2.5% protein and 200-350 mg vitamin C per 100 g of pulp. Fresh
green fruits are sometimes used to make jams.
The dried fruits
contain 20-35% sugars (just under half that being sucrose, the rest
fructose and glucose) and are rich in Vitamin C. Oriental food shops
often sell Chinese dates which have been boiled with sugar and honey
— the most popular Chinese way of eating them. In Korea, jujube
flour is used in the preparation of 'kochujang', a fermented hot
pepper-soyabean paste that resembles miso. An edible oil can be
obtained from the seed — though presumably yields are low as the
kernel is small.
The fruits are also medicinal (being anodyne,
anticancer, pectoral, refrigerant, sedative, stomachic, styptic and
tonic), and widely used in Chinese herbal medicine for arthritis and
insomnia. They are often used in mixtures with other species parts and
such mixtures have been shown useful in treating hepatitis B. They are
used in the Himalayas as an antidote to aconite poisoning and for
nausea and vomiting; for abdominal pain during pregnancy; and
externally in poultices for wounds.
The fruits were often used
(possible in the boiled-with-honey form) in Britain to alleviate coughs
and sore throats, and were formerly imported into Britain in large
quantities from Southern France for this purpose.
The seeds are
used in Chinese medicine (being hypnotic, narcotic, sedative, stomachic
and tonic) for insomnia, amnesia, vertigo; the root is used for
dyspepsia, as a powder for wounds and as a febrifuge. The plant is
widely used in China as a treatment for burns.
The leaves are
also medicinal, being astringent, febrifuge and laxative and prescribed
in the Himalayas for scabies and throat troubles. A broth is made from
the leaves in Tadjikistan and used for treating liver, kidney and
stomach problems, and to improve vital functions. In China they are
used for fevers and are said to promote hair growth.
The wood of
the tree is very hard and durable, and used to make agricultural
implements and for turnery. It makes good fuel and charcoal.
The leaves are used as a fodder for sheep and goats in the Himalayas. They have also been used for silkworm fodder in China.
In
China, jujube is widely used in shelterbelts, with over 200,000 ha
planted, with optimum spacing of rows 3.7 m wide (presumably 2 lines of
trees), with alleys between rows of some 14 m width, where cereals like
wheat are grown. Jujube is also used to stabilise mountainous slopes
from erosion, and is regarded in Central Asia as one of the best crops
for this. The leaves have an antifungal effect against several fungal
diseases including leaf spot of cotton & onion (Alternaria tenuis) and leaf blights (Helminthosporium sp.). The jujube is also an attractive ornamental tree.
Cultivation
Jujubes
can be grown for fruit production in warm temperate or subtropical
climates; hot dry weather is required for good fruiting. In areas where
there are prolonged or severe frosts, the plants need the protection of
a cool or intermediate glasshouse if fruiting is desired. In Britain,
lack of summer heat can often prevent good fruiting and growth.
Grow
in any well-drained soil, including alkaline and saline soils, in sun.
Jujubes like low humidity during the growth season and a dry soil in
winter. Pot-grown trees may need regular root pruning to prevent the
formation of a dominant long tap root. Jujube orchards should be
planted at 7-8 m by 4-5 m — the larger spacing on more fertile
soils and for more vigorous trees. Growth in Britain is about 2 m in 10
years.
Pruning should be carried out during dormancy in winter.
Fruit is borne on the current season's growth, hence there is no danger
of pruning off fruiting wood; pruning should concentrate on removing
dead or dying wood, and keeping the tree open and well ventilated.
Initially it may be wise to select a framework of 3-4 branches in a
pyramid form.
In China, girdling is commonly used to increase
yields by up to 200%. A circular strip of bark is either removed or
reversed on the main trunk of the tree. This procedure also causes the
tree to set fruit earlier and ripen at the same time — it
shortens the harvest time. The harvest time itself can be manipulated
by girdling at different times. After a tree has been girdled every
year for many years, it can be cut off totally and allowed to regrow.
Fruiting
on grafted plants starts after 2-4 years; seedlings may take 3-7 years.
The first few crops do not give a true indication of eventual fruit
size. Although trees are usually self-fertile, fruits are bigger and
more numerous with cross pollination.
Harvesting can begin as
soon as the green fruits develop a few brown spots on the skin —
they will then fully ripen off the tree; if you have dry conditions,
then leave them on the tree to ripen and harvest them as they fall to
the ground. The fruits ripen gradually (over a month or more) and not
all at once, and should be picked or shaken every few days over this
period. In China, harvest normally takes place early in the morning
before the dew dries — this is supposed to improve the flavour
and texture of harvested fruits. Yields vary tremendously but can
average 45 kg per tree or more for mature trees.
Fresh ripe
fruits will keep for 1-2 months at 10°C or for 1-4 weeks at room
temperature; dried ripe fruits will keep for a year at cool
temperatures and 50% relative humidity. They should be kept in unsealed
containers. There are few pests or diseases.
In humid climates,
fruits should be picked when starting to turn brownish-red and dried
either in a solar dryer and/or in an oven at 45 °C, stirring. If
not picked, rain and humid weather can cause the skin to crack, and
then fungi can develop in the cracks.
Cultivars
Most of these originated in China and arrived in the West via the
USA in the early 20th Century. China currently has over 400 superior
cultivars, although only a handful are obtainable in the West. Seedling
trees come relatively true to their parent, although they take a few
more years to bear fruit.
Admiral Wilkes: Fruit elongated, 50 mm long, very late to ripen.
Ant Admire: Fruits medium sized, narrow, elongated, very sweet; mid season ripening. From China.
Chico:
Fruits small, round, often seedless (seed is round when present), good
to eat green when crisp and acid; tree thorny, needs hot location. A
Californian selection.
Davis: Fruits of excellent flavour; productive tree. From the USA.
GA 866: Fruits elongated, 50 mm long, very sweet, mid-season ripening. Tree has few thorns. From California.
Geant Sloboda: A selection from the former USSR.
Honey Jar: Fruits very small (under 25 mm across), round, extremely sweet both fresh and dried. From China.
Jin:
Fruits very uniform, elongated, 50 mm or more in length, very small
seeds. Dried fruits are very chewy and date-like. Ripens early; hangs
on the tree well after drying.
Lang: Fruits large (up to 50 x 40
mm), pear shaped, with a thin shiny skin and sweet, melting plentiful
flesh with a hint of caramel flavour; tree large, upright, early
bearing, generally has only a few thorns. Good fresh, excellent dried.
Mid-season ripening. Origin: China.
Li:
Fruits very large (to 50 mm in diameter), round, excellent flavour,
good to eat green, flesh sweet and crisp, and with a small stone, early
season ripening; will ripen if picked at the yellow-green stage. Tree
large, spreading, suckering. Origin: China.
Redlands 4: Fruits large, round, like Li but larger; excellent sweet flavour and crisp texture; mid season ripening. From California.
Sherwood:
Fruits very large (40-50 mm long or more), flesh of excellent quality,
dense; very late ripening. Will keep for 6 weeks in refrigeration. Tree
with small or no thorns, very productive. From Louisiana.
Shui Men:
Fruit medium sized, elongated, sweet-acid flavour, good fresh or dried;
ripens mid season. Tree a good bearer, with small thorns. Origin: China.
Silverhill (Silverhill
Round, Tigers Tooth): Fruits large (25 mm across by 40-50 mm long),
elongated (plum shaped), with sweet solid flesh, good for drying, mid
season ripening; tree large with few suckers or thorns, a prolific
bearer. From the USA (Georgia).
So:
Fruit round, of excellent flavour. Tree branches grow in a zig-zag
manner.
Sugar Cane: Fruits small-medium sized, oval, 25 mm long, very
sweet and crunchy, very dense, small seeds. Tree thorny. From
California.
Sweet Meaty: Fruits round, meaty; very late ripening. Tree with large thorns.
Tajanczao: A selection from the former USSR.
Texas Tart: A high acid jujube. Origin: Texas.
Yu:
Fruits large, elongated, tapering at the bottom; flesh sweet, firm,
good keeping qualities. Tree tall with few side branches and large
leaves, and few thorns. Origin: China.
Other cultivars grown in
the former USSR (particularly Tadjikistan, Uzbekistan, Azerbaijan)
include Kitaiskij N selections, Azerbaijanskij N22, Apsheronskij,
Mardakyanskij N1, Tadjikskij N24 and Shirvanskij.
Propagation
Seed
propagation is fairly easy. Jujube seeds have a hard, rough, pointed
outer shell which has a distinct suture line aligned from end to end.
This shell needs to be removed to facilitate reliable germination; the
best way is to carefully align the suture in the blades of a pair of
secateurs and cut firmly — the seed usually comes out unscathed
from this operation!
The naked seeds are then not dormant and
should be sown immediately in the warmth; germination takes place over
the next 2-5 weeks. A few weeks of cold stratification sometimes aids.
First year growth can reach 20 cm. There are about 2400 seeds per kg.
Cutting
propagation is difficult but possible. Take greenwood cuttings in
summer about 15 cm long, just as the base is starting to harden, and
use mist and bottom heat. The success rate may be as low as 10%, but it
may be worth it to get trees on their own roots, whose suckers will be
identical to the mother tree.
Cultivars of Z. jujuba are usually propagated by grafting onto jujube seedlings or seedlings of the related Ziziphus rotundifolia
— the latter limits top growth and is better suited to pot
culture, but is not very hardy. A whip and tongue graft is used with
the previous season's wood at least 7 mm thick. Jujubes can sometimes
be propagated by root cuttings — success depends on the cultivar.
Suppliers UK
Agroforestry Research Trust, 46 Hunters Moon, Dartington, Totnes, Devon, TQ9 6JT. Seed & sometimes seedlings.
Burncoose & South Down Nurseries, Gwennap, Redruth, Cornwall, TR16 6BJ.Tel: 01209 861112. Supplies 'Lang'.
Hollington Nurseries, Woolton Hill, Newbury, Berks, RG20 9XT. Tel: 01635 253908. Supplies 'Lang' and 'Li'.
Reads Nursery, Hales Hall, Loddon, Norfolk, NR14 6QW. Tel: 01508 548395. Supplies 'Lang' and 'Li'. Suppliers USA
Edible Landscaping, PO Box 77, Afton, VA 22920. Tel: 804-361-9134.
Roger & Shirley Meyer, 16531 Mt. Shelley Circle, Fountain Valley, CA 92708. Tel: 714- 839-0796. Supply many rare cultivars.
References
Bean, W J: Trees and Shrubs Hardy in the British Isles. John Murray, 1974.
Burmistrov, L: Jujube in Russia. Fruit Gardener, Vol 26, No 4 (Dec 1994), p4.
Ciminata, P: Jujube talk. Quandong, Vol 22 No 1, P 14-16.
Duke, J & Ayensu, E: Medicinal Plants of China. Reference Publications, 1985.
Facciola, S: Cornucopia II. Kampong Publications, 1998.
Glowinski, L: The Complete Book of Fruit Growing in Australia. Lothian Books, 1997.
Grange, M & Ahmed, S: Handbook of Plants with Pest-Control Properties. Wiley, 1988.
Huxley, A: The New RHS Dictionary of Gardening. Macmillan Reference, 1999.
Johns, L & Stevenson, V: The Complete Book of Fruit. Angus & Robertson, 1979.
Krussmann, G: Manual of Cultivated Broad-Leaved Trees and Shrubs. Batsford, 1985.
Meyer, R: Jujube Variety List. Quandong, Vol 19 No 2, p 21-22, 1993.
Parmar, C & Kaushal, M: Wild Fruits of the Sub-Himalayan Region. Kalyani Publishers, 1982.
Reich, L: Uncommon Fruits Worthy of Attention. Addison-Wesley, 1991.
Wertz, H: Jujube notes — Propagation, Drying & Hardiness. Pomona, Vol xxiv No 3, p 61-62.
Whealy, K & Demuth S: Fruit, Berry and Nut Inventory. Seed Saver Publications, 1993.
[Based
on an article published in Agroforestry News, Vol. 9 No 1, October
2000]. Agroforestry News: A2768. Agroforestry Research Trust: A2769.
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