1539

2: Edible fruits and nuts

Punica granatum L.

Sp. Pl.: 472 (1753).

PUNICACEAE

2n = ?16, 18

Pomegranate (En). Grenadier (Fr). Indonesia: delima. Malaysia: delima. Philippines: granada. Burma: salebin, talibin. Cambodia: totüm. Laos: ph'iilaa. Thailand: thapthim (central), phila (Nong Khai), bakoh (northern). Vietnam: lu'u, thap lu'u.

The pomegranate is native to Asia, particularly to Iran, Afghanistan and the Himalayas. From there it was introduced and naturalized in the Mediterranean region, where it has been cultivated since ancient times. Now it is grown throughout the tropics and subtropics.

The fruit is eaten fresh or the juice is extracted to prepare a refreshing, thirst-allaying drink ('grenadine'). In Asia the juice is also thickened to a syrup which is used as a sauce. The fruit is an old symbol of prosperity and fertility; in the form of 'rujak', a traditional fruit salad, it plays a prominent role in the pregnancy ceremony in Java and other parts of Indonesia.
However, fruit yield and quality tend to be poor in South-East Asia and the tree — almost every part of the plant — is more often used for medicinal purposes; pomegranate figures in many oriental accounts of materia medica. Gargles are prepared from the dry rind of the fruit and fruit juice is given to persons suffering from fever. In Asia the bark of the branches and roots is a well-known remedy against tapeworms and other intestinal worms. The astringent properties of bark, leaves, immature fruit and fruit rind are used in decoctions against diarrhoea and dysentery. The astringency is due to the presence of tannins; the bark, leaves and fruit rind are in fact good sources of tannin. The rind also provides a dye used as ink, to dye cloth, or — in former times — by women to stain their teeth black.
Pomegranate is also appreciated as an ornamental plant; some dwarf types are purely ornamental.

The fruit is grown commercially mainly in subtropical areas; it is also traded internationally, e.g. to Europe from the Near East. In South-East Asia pomegranate is purely a home garden plant; appreciable quantities appear in the market in Thailand only. Malaysia actually imports pomegranates.

Analysis of the edible portion in India showed the following composition per 100 g: water 78 g, protein 1.6 g, fat 0.1 g, carbohydrates 14.5 g, fibre 5.1 g and minerals 0.7 g. Other analyses indicate an invert sugar content of up to 20% of which 5—10% glucose, citric acid (0.5—3.5%), boric acid (trace) and vitamin C (4 mg/100 g). The yellow dye in the rind is gallotonic acid. Tannin content is highest in the root bark (28%), but the dried rind also contains much tannin (up to 26%). Alkaloids in the bark belong to the pyridine group.

Deciduous shrub or small crooked tree, up to 6(—10) m tall, often much branched near the base; branches often ending in a spine, but also with axillary spines, sometimes leaf-bearing themselves. Leaves mostly opposite, sometimes subopposite or clustered, oblong-lanceolate, 1—9 cm x 0.5—2.5 cm, base acute or obtuse, margin entire, apex obtuse or emarginate, shiny above, firmly herbaceous with prominent midrib beneath; petiole very short. Flowers 1—5 at the top of the twigs, waxy, 4—5 cm long and wide; calyx and receptacle 2—3 cm high, red or pale-yellow, fleshy, acutely 5—8-lobed; petals 3—7, crinkled, red, white or variegated; stamens numerous, style surpassing the stamens. Fruit a globose berry, 6—12 cm in diameter, crowned by the persistent calyx, very variable in colour from yellow-green to black-violet, skin leathery; the interior is separated by membranous walls and white spongy tissue into compartments packed with transparent sacs, each filled with juicy pulp and a seed. Seeds obtuse-angular, red, pink or yellow-white.
In the subtropics the trees flower in spring along with a flush of shoot growth; fruit ripens in the later summer after 5—7 months. While the fruit is growing a summer flush provides the new shoots which will flower during the next spring. In the tropics growth and flowering are still more or less seasonal, but there may be 3 flushes per year, each of which may bring on flowering; only a flush which coincides with a load of growing fruit is unlikely to give bloom.
The flowers are borne terminally and on short side shoots (spurs). They are pollinated by insects. Fruit set improves in the order self-pollination, open pollination, cross-pollination by hand. Under favourable conditions more than half the flowers may set fruit.
Numerous cultivars exist, e.g. 'Ahmar', 'Aswad' and 'Halwa' in Iraq, 'Bedana' and 'Kandhari' in India, 'Wonderful' and 'Grenada' in the United States. The Japanese dwarf pomegranate, Punica granatum L. var. nana Persoon, is a hardy ornamental grown in pots. Other ornamental cultivars, often of double-flowered forms varying in colour from white to red and purple, are e.g. 'Multiplex' and 'Variegata'. According to the colour of the fruit, pomegranates are divided into four groups: dark red, yellow-green, black-violet and white. In Socotra, an island off the Somali coast, the little known Punica protopunica Balf.f. occurs, the only other species in the genus.

The pomegranate is a hardy subtropical species, surviving low winter temperatures (—10°C). The best quality fruits are produced in areas with cool winters and hot, dry summers; it does not fruit well in very humid climates. Under dry conditions irrigation is needed to sustain high yield levels. The tree tolerates soils on which most other fruit crops do not thrive, including calcareous and alkaline soils.
In South-East Asia the tree grows well up to 1600 m elevation on a wide range of soil types; in wetter regions the tree becomes evergreen, flowering and fruiting becomes protracted and fruit quality is inferior.

Trees grown from seed are variable and clonal propagation through hardwood cuttings or air layers is recommended; the latter method is common in South-East Asia. Layers can be separated after 3—4 months when they are properly rooted. Layers can come into bearing quickly; they are often sold while in bloom.
For orchards in India spacings of 5 m x 2 m to 5 m x 5 m are advised. The lower side shoots are removed at planting and the other laterals cut back to create a trunk, and to instill enough terminal vigour to suppress suckering which would otherwise lead to reversion to a shrubby habit. Suckers grow for extended periods and are too juvenile to flower; hence, they spoil the tree habit and grow at the expense of the bearing wood.
In a monsoon climate timing of bloom can be manipulated by withholding irrigation for about 2 months; flowering occurs a month after resumption of irrigation. Ploughing or root pruning when the dry spell has started strengthens the effect. Manure is applied at the end of the dry spell.
A number of pests and diseases have been recorded, the most important being the pomegranate butterfly Virachola isocrates which has fruit-boring caterpillars that are a real threat to the crop in India, and fruit rot caused by Phomopsis fungi which come to the fore in wet climates. The fruit borers are hard to control since single eggs are laid on flowers or on the calyx slips of the fruit and the young caterpillar soon eats its way into the fruit, its small size making entry hard to detect. The fruit can be bagged to protect it; pesticide applications should be based on careful monitoring of the population of butterflies (light traps) and progress of egg deposition. Phomopsis rot spreads through the seed of infected fruit, hence infected fruit and flowering twigs should be removed. Fungicides provide adequate control. Pomegranate is one of the hosts of the wax scale Ceroplastes sinensis.
The fruit may crack upon ripening, but immature fruit is of inferior quality and fruit should not be harvested before it attains the yellow base colour. The fruit does not detach easily and has to be clipped with pruning shears. In the leading production centres yields of 100—150 fruit (17—25 kg) per tree or 10 t/ha per year are considered good crops for mature orchards. The fully ripe fruit ships and keeps well.

The prospects for commercial pomegranate production appear to be bright. Favourable factors are the expansion of export markets and the fact that the fruit is easy to handle and has a long shelf life. Further cultivar improvement in the Near East and India, where most orchards still consist of seedling trees, is needed. In South-East Asia, however, the pomegranate will continue to be grown because of its importance in traditional life and medicine and its ornamental value rather than as an orchard fruit because the climate is not favourable for high yields or acceptable fruit quality.

Backer, C.A., 1951. Punicaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana, Series 1. Vol. 4. pp. 226—228.
Badizadegan, M., 1975. Growth of pomegranate (Punica granatum L.) as affected by soil moisture tension. Journal of Horticultural Science 50: 227—232.
Perry, L.M., 1980. Medicinal plants of East and Southeast Asia: attributed properties and uses. MIT Press, Cambridge, Massachusetts. 620 pp. Sardianto & Sucipto, 1988. Delina putih dan morah [White and red pomegranates]. Trubus 19(221): 180—181.

Sudiarto & Mien A. Rifai

Sudiarto & Mien A. Rifai, 1991. Punica granatum L.. In: Verheij, E.W.M. and Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2: Edible fruits and nuts. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea