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Friday, May 31, 2013

Growing Pomegranate varieties

Growing Pomegranates in Western Australia


by John Burt, South Perth

General

The pomegranate (Punica granatum) is native to Iran through to north India. The main areas of world production are Turkey, Spain and California. It is an attractive deciduous large shrub/small tree, up to 4 to 5 m high. The flowers, fruits and autumn foliage are ornamental and it is often planted in home gardens from Carnarvon to southern areas of the State.
At present, the pomegranate is commercially harvested on an insignificant scale in Western Australia. The main annual imports are from California in November and December.
oldpomtreewanneroo.jpg
Fig 1 Old pomegranate tree in a mixed orchard in Wanneroo

Climate


Pomegranates would probably grow best commercially from Geraldton to Albany. They grow best in warm areas, with temperatures up to 38 °C. In inland areas, temperatures can be high and fruits can suffer from sunburn. Rainfall in summer and early autumn should be low. Established plants will survive frosts to minus 10 °C. Flowering occurs in late spring, when there are no frosts. Pomegranates do not like high humidity.

Soils

Soils can be variable, but must be well drained.
The pH (by the water system of measurement) should be 5.5 to 7.0, but the plant will grow well in slightly alkaline soils.

Varieties

There are many varieties, with a range of quality varying from very sweet (bland) to very acidic flavours and with soft seeds, medium hard seeds or hard seeds. The best quality pomegranates have a good balance of sugars and acidity, and soft seeds, which can be consumed with the pulp.

A pomegranate variety observation was conducted at Medina Research Centre in the 1990's. Fruit quality and comments are shown in Table 1 and yields were not recorded:
Table 1 Variety Observation at Medina Research Centre in the 1990's.

VarietiesExternal appearanceInternal appearance/juiciness,
acidity
Comments
Gulosha Azerbaijani, Large size, good external appearance (light pink/red skin). Large red grains.
Juicy.
Good variety.
Gulosha Rosavaya Large size, good external appearance (light pink skin). Large, red grains.
Juicy.
Best variety for combination of sweetness, acidity and external appearance.
Wonderful Medium size. Claret red skin. More acidic than Gulosha rosavaya.
Red grains.
Next best variety to Gulosha varieties, but is smaller and more acidic. Most common variety in California. Better for juicing.
Victorian Giant Large size, not very attractive skin. Grain is not highly coloured, not juicy, mild flavour. Poor variety.
Berri Large size. Skin is not attractive. Not juicy, too sweet, bland flavour. Poor variety.
Veles Medium size. Squarish shape, pink red skin Juicy, rich flavour, but very acidic May be suitable for processing.
Griffith Large size Claret red skin. Red grains, rich flavour, but slightly too acidic Fairly good variety.

Obtaining plants

Pomegranates are easily struck in potting mixture in July and early August from 20 to 30 cm cuttings when the plants are dormant. Leave the top 1 to 2 buds exposed. The cuttings should be 6 to 12 mm thick.

Ten varieties are available from Lewis Horticulture (08 8380 9598), Box 798, Virginia, South Australia 5120. These are sold in 9 cm pots, at a cost of less than $10 per plant.
Keep the plants in a sheltered position in a nursery and use a slow release, complete, fertiliser. Plant in spring, 13 to 15 months later, when the plants are 60 to 100 cm high.

Field Management

Incorporate compost into the hole before planting.

In early spring, plant in rows that face north. Space at 4 to 6 m by 2 to 6 m. Plants bear fruit on the terminal shoots of branches which receive good light. Production will decrease if spacing is too close and the branches are shaded due to the inter-mingling of branches from adjacent bushes.
Mulch plants with compost and/or organic material and apply occasional light applications of an organic manure for at least the first three years.
Wind protection is beneficial to ensure good growth. Permanent windbreaks of river she-oak (Casuarina cunninghamiana) will protect plants from winds, but sucker re-growth must be removed every year.

Fertilising

The fertiliser needs of the pomegranate are moderate compared with most fruit trees. For the first four years, apply a good, mixed fertiliser each month from August to March. One suitable commercial product contains 15% N, 2.2% P, 16.6% K, 1.2% Mg, 8% S and six trace elements. Apply a total of 0.5 g per tree in year 1, 0.75 kg in year 2, 1.0 kg in year 3 1.5 kg in year 4, 2.5 kg in year 5 and 3.0 kg from year 6 onwards.
Extra applications of zinc sulphate at 2g/L may need to be sprayed onto plants grown on alkaline sandy soils. Extra manganese and iron sprays may also be needed.
A leaf analysis from a proprietary laboratory will give a guide whether the nutrients in the leaves are at deficient, satisfactory, optimum, high or toxic levels. The results must be compared with other fruit trees, as there are no comparable standards for pomegranates.

Irrigation

The pomegranate has good drought tolerance and will also withstand short periods of waterlogging. Mature plants with low level sprinklers or drip irrigation need about 5,000 to 8000 kL of water per hectare per year, from September to April.

Pomegranates have a higher salt tolerance than most fruit crops. The water quality should be less than 1000 ppm total soluble salts for best results, but plants will tolerate more than 2000 ppm total soluble salts.

Pruning

Shrubs are initially pruned at 60 cm high to form 3 to 4 main stems. For the first three years, in winter, cut back slightly the tips of new shoots, to promote the development of side shoots. Remove suckers and water shoots, especially at the base of the stem. In winter, remove crossing branches

Pests and diseases

Pomegranates have few pest and disease problems.

Mediterranean fruit fly occasionally damages fruit where the fruit is cracked and a baiting program may be needed. Fenthion (Lebaycid®) can be used to control this pest. The presence of this pest in Western Australia means that the whole fruit cannot be exported to countries where this pest is not found.
Aphids can result in a twisting of young shoots and leaves. Scale insects can damage the leaves and stems. Endosulfan (i.e. Thiodan ®) will give some control of this pest.
Parrots will attack the fruit if the shell is cracked.
Rats can damage the fruit.
Root knot nematodes can damage the roots.
Heart rot is often found in parts of the fruit and this is not obvious until the fruit is opened. It is believed to be caused by the fungal pathogen, Alternaria sp which initially attacks the flower. It is difficult to control.

Weeds

Mowing or spraying to manage weeds is preferred to cultivation in older plantings to avoid root damage. Planting or a cover crop mixture of legumes and grasses in the inter-row is advisable to manage weeds and improve soil structure.

In the plant rows, apply glyphosate (e.g. Roundup®) around the bushes, but avoid spray drift onto the leaves of the bushes, especially with young plants. This is a contact, non residual, herbicide that will kill most existing weeds. For grass control , fluazifop (Fusilade®) is registered to control existing weeds.

Fruiting

Pomegranates have attractive flowers which bloom for a long time from late spring to summer. Flowers occur on spurs of 2 to 3 year wood and also on new wood.
Pomegranates are self and cross pollinated.
The fruit is a false berry. It consists of many close packed red grains (arils), and segments which are separated by a non-edible white pith. The arils contain a seed surrounded by an edible juicy pulp. Fruit consists of 78 per cent water, 8 to 21 per cent sugars, 1.3 per cent protein, 0.9 per cent fat and 0.3 to 0.5 per cent acid.
Plants do not commence to bear well until the third to fourth year after planting. Fruit matures from March to May.
Fruit are easily bruised and should be carefully handled. It will crack when too mature, or if there is too much rainfall in autumn, high humidities, poor watering, or high winds.
Pick the fruit with clippers, just before before the fruit has started to crack. The fruit should make a metallic sound when tapped. Clip the stem close to the fruit. The fruit will not ripen off the bush. Mechanical harvesters are not available for pomegranates.
Yields are 10 to 20 t/ha, with 100 to 200 fruit per plant.
Pomegranates will store for about 1 to 2 months at ambient temperatures, or kept for seven months at 0 to 5 °C and 80 to 85 per cent relative humidity. The fruit improve in storage, becoming juicier and more flavoursome
Bushes are long-lived.

Uses

Pomegranates have a high level of polyphenols or anti-oxidants and are now being promoted as a health food, especially for the juice market.

Overseas, pomegranates are often marketed not as whole fruit, as in Australia, but as arils or juice.
Machines are available from Israel at a cost of $US 250,000 to remove the arils at 16 pomegranates per minute and less than 5 per cent are damaged. Fruit are held in cool storage before the arils are extracted. With vacuum packaging, arils can be kept for six months. Juice can easily be extracted from the separated arils. There is potential to market the juice on domestic and export markets. The percentage of juice in the fruit is about 45 to 65 per cent. The juice is also used to produce Grenadine, which is used in cocktails and to produce wine. After extraction, the waste material can be used for pharmaceuticals and cosmetics.
Disclaimer
The Chief Executive Officer of the Department of Agriculture and Food and the State of Western Australia accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.

Ref: http://www.agric.wa.gov.au

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