Carob

24.05.17

Native to the Mediterranean region, the carob (Ceratonia siliqua币游注册) is a flowering evergreen tree cultivated mainly for its edible pods and seeds, but also grown as an ornamental garden specimen. Commonly known as St John’s bread or locust bean, it is a member of the legume family, although it does not fix atmospheric nitrogen.

币游注册Carob trees can live for over 100 years, grow to 15m and produce a trunk girth of up to 3.5m. The leathery leaves grow in four to five pairs of oval-shaped leaflets; new growth is bronze coloured and mature leaves are dark green on the upper surface and light green to grey underneath. The trees can be male, female or hermaphrodite (both sexes).

Facts and figures

  • Carob trees are best grown in conditions similar to the Mediterranean climate and alkaline soils from which they originate, and are tolerant of drought, salinity and frost
  • The Australian carob industry has been evolving since the early 1980s, with the export industry only established in 2014, production levels are low compared with other participants in the world market
  • Carob trees, seeds and pods, have a multitude of uses, spanning dozens of industries
  • A slow growing crop, carob trees can take up to 10 years to reach full commercial production levels

Production status

While carob is grown in six states and territories of Australia, the key production regions are western New South Wales, southern South Australia and the northern agricultural region of Western Australia. New plantings are in western areas of New South Wales, Queensland and Victoria, and in the agricultural areas of South Australia and Western Australia.

The growing area is about 400ha, mainly located in the states of South Australia (34%), and Western Australia (20%). In the other states there are an estimated 30,000 seedling carobs within and adjacent to fenced grazing areas for sheep and cattle.

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Map of current and potential growing regions

Uses

Overseas, carob seeds are used as a cash crop, while the discarded pods are fodder for pigs and other animals. The carob seeds are 35% gum (locust bean gum or ceratonia), which is processed and used as a gelling agent, stabiliser or emulsifier in ice-cream, yoghurts, dessert fruit filling and salads. It is also a component used in thickeners and to prevent sugar crystallisation in confectionery.

Products manufactured using the ground carob seed gum include inks, paints, textiles, oil well drilling additives, explosives, ceramics, paper, adhesives, chewing gum, pet foods and cosmetics. Oil extracted from the seeds (algaroba) is used in the pharmaceutical industry.

Carob is valued for medicinal purposes due to its high pectin and tannin contents, which are both useful for digestive ailments. The oil also contains lignans, which have many benefits including antiviral, antifungal, antibacterial and anti-inflammatory qualities.

币游注册The pods, which can have a sugar content of up to 50%, can be eaten fresh when they are young and green, however they are more often harvested when mature and dark, then dried and kibbled (coarsely ground) to separate the seed from the pulp. The kibble, which is high in calcium, fibre and natural sugar, is sometimes sold as a healthy snack food or in products like trail mix, and can be used as high-energy stock feed (containing 21% protein).

币游注册The kibble may be milled or ground and sieved to produce caffeine-free carob powder, which is a natural sweetener used as a healthy substitute for cocoa powder in baking and food manufacture, as a food stabiliser, or a darkening agent. It is also used to make molasses and alcohol, and as a substitute for coffee.

币游注册Carob pods on the tree are used as supplementary stock feed for grazing stock (cattle, sheep, goats and donkeys), particularly when trees are planted in windbreaks along the edge of the paddock. The tough bark is resistant to ring-barking by grazing stock. Although carob is not a nitrogen fixing species it is quite deep rooted, and  tolerates considerable drought.

Carob trees are often used in landscaping for street planting, privacy screens and as an ornamental shade tree; as well as on farms to provide windbreaks around homesteads, orchards and paddocks. The tree is fire resistant and able to regenerate after burning. In Spain carob trees were planted near villages to slow down the pace of grass fires.

A minor carob product is the moderately dense wood (carouge), which is used as a specialty furniture timber and in some cases as firewood.

Production Requirements

Growing regions

Grown in all five states and the Northern Territory, the biggest carob orchards are in western New South Wales, southern South Australia and the northern agricultural region of Western Australia. Newer plantings are largely in the western areas of New South Wales, Queensland and Victoria, and in the agricultural areas of South Australia and Western Australia. These regions have a similar climate to the Mediterranean region where the carob originated.

Soil type

Carob trees grow best in high pH limestone and other alkaline soil types with good subsurface drainage, including on a variety of well-drained and well-aerated soils, including sands and clay loams. Carobs also do well on rocky dry sites where their tap root can penetrate to reach water. They will not tolerate heavy clay and waterlogging is likely to induce stunting or death.

Carobs prefer a soil pH(water) level between 6.2 and 8.6, and are known to tolerate slightly saline conditions.

Climate

The carob tree is best suited to temperate and semiarid regions of Australia, similar to the Mediterranean region, but it can also grow well in subtropical areas. The tree flowers in autumn, and the pods develop through winter, spring and summer, and ripen for harvest in late summer. In order to achieve maximum sugar content before harvest, hot dry weather during the late summer and autumn ripening period is critical.

Carob trees are suited to regions of 250–600mm of annual rainfall but 500mm is considered ideal. Carobs are drought resistant and have an extensive tap root system that can develop 20m deep in the soil. Carobs grow well in arid areas with artesian water supplies and respond well to supplemental irrigation. Low rainfall in summer reduces the risk of fungal attack as the pods reach maturity, which results in sugar fermentation.

币游注册Carob trees thrive in hot summers and can withstand maximum temperatures up to 50°C with a relative humidity of 6%. They do not tolerate severe frosts but are less frost sensitive than citrus (as a potential environmental indicator). Temperatures under -4°C can kill or injure young trees by damaging their buds and small branches. Winter temperatures below -8°C will damage the mature plant and retard fruiting.

币游注册While carob can be found growing in warm, coastal environments, trees in these areas do not have regular winter dormancy, making propagation by budding and grafting difficult, as well as affecting yield.

Varieties

币游注册The development of carob varieties is limited globally, however preliminary breeding is occurring in Spain to improve agronomic and processing qualities, such as size, yield and sugar content of the beans, and also the size, hardiness and maturation rate of the tree.

A number of varieties are cultivated and available in Australia, including 11 of the best European and American selections that were brought to Australia in the early 1980s. Successful Australian-bred varieties include Irlam and Waite, while others (originating from Cyprus, Tunisia, Mexico and Spain) include Tylliria, Sfax, Casuda, Badan and Cypriot. Also available in Australia are Clifford, Santa-Fe, Laguna, Molino, Tantillo, Bath, Maitland and Amele.

Planting and crop management

币游注册Carobs seeds or seedlings are planted in spring in full sun, with carob seeds germinating best at a soil temperature of 22–26°C. Polythene socks or ‘growtubes’ can accelerate the growth of seedlings. Grafted trees are not yet readily available in Australia and will speed up the orchard establishment time, as carob is a very slow-maturing crop, taking 6–7 years before bearing fruit. A suggested spacing of 10x10m (100 trees/ha) allows for orchard maintenance and maturation space for each plant.

币游注册Pollination can be maximised by planting one hermaphrodite tree (e.g. Clifford or Santa Fe) for every eight females, or grafting male or hermaphrodite scionwood onto female trees. Hermaphrodites have a longer flowering period than males.

Slow release fertilisers or manures applied at planting will provide adequate nutrition for seedlings. Application of nitrogen, phosphorus and zinc may be beneficial to mature trees, however individual tree requirements should be monitored through leaf tissue analysis, and fertiliser rates should be tailored to individual sites. In Spain, leguminous annual crops are frequently grown between carob trees, and up 3–4 tonnes of manure per hectare are applied every 3–4 years.

Pruning is required to control suckers during the early stages of growth, and again later when branches are damaged or become overcrowded. Irrigation can boost production when rainfall is inadequate for commercial orchards. Further information on planting and crop management is provided in Carob Agroforestry in the low rainfall Murray Valley, and the website of Carobs Australia Inc.

Weeds, pests, and diseases

币游注册There are no major pests and diseases of carob in Australia, other than the carob moth, which has become a major pest of carobs in both Western Australia and South Australia. Carob moth attacks a range of hosts, including acacia, and fruit and nut trees. Removal and destruction of larvae infested pods from the carob trees is important and organic insecticides can be applied to kill the larvae.

Routine spray schedules can prevent build-up however there are no pesticides registered specifically for carob moth. Affected pods can be heat treated and put into insect-proof or cold storage. Moth traps, lures and mating disruption techniques can be installed to control the adult moths. More information is provided in the Western Australia Department of Agriculture and Food’s fact sheet , and by contacting their offices.

A potential pest of carobs is citrus red scale, which is controlled by the Aphytis wasp. The Rutherglen bug has been reported to destroy seedlings in Western Australia through defoliation, so close monitoring of establishing seedlings is necessary in regions where the bug exists. Fungi will attack carob seed and seedlings, however establishing orchards with grafted stock will eliminate this issue.

Grazing animals are a pest for seedlings and should be excluded from young orchards. Rodents may attack stored pods and kibble, which should be kept in rodent proof storage facilities.

Despite potential threats, Australia’s largest and most successful grower and exporter of carob uses no insecticides or pesticides, and has achieved organic certification.

币游注册 . Information about certification can be found at, but is not limited to, the websites of  and .