Macadamia

24.05.17

Macadamia belong to the ancient Gondwanan family of plants, Proteaceae, along with banksias and grevilleas. There are four species of macadamia in the world, all of which are native to Australia and only two are edible – Macadamia tetraphylla and Macadamia integrifolia. Both species are endemic to subtropical rainforests, occurring naturally between the latitudes 25° to 31° south.

Overview

The species most commonly used for the production of nuts in Australia and overseas is M. integrifolia. For commercial production, it has been crossed with or grafted onto other Macadamia species, particularly M. tetraphylla, to achieve varieties better suited to commercial production, which are often smaller than wild-growing species.

In the wild, M. integrifolia can grow to 20m in height and attain a similar dimension in foliage width — giving the tree a rounded shape. The leaves are thick and leathery, growing to 14cm and arranged in groups of three. The tree produces flowers from August to October, with sprays (racemes) about 30cm in length, each with 40–50 flowers that eventually produce about 15 nuts. The nuts are round with a green fibrous husk and about 2.5–3.5cm in size; each contains a smooth hard brown nut-shell containing a white edible kernel.

The first macadamia orchard was established in Australia during the 1880s but the industry did not develop on any scale until the 1970s. Australia is one of the world’s largest macadamia producers, however commercial-scale production was first achieved in Hawaii in the 1930s, and Hawaii remains a major world producer.

The macadamia industry is established yet still growing and has a strong representative body, the Australian Macadamia Society, which is driving development of the industry at commercial, environmental and political levels for its 600 or so members.

Facts and figures

  • Macadamias evolved over 60 million years ago in Gondwana Land and there are four species endemic to the eastern seaboard of subtropical Australia
  • Australia produces around 30% of the world’s macadamias and exports to more than 40 countries
  • There are around 22,000ha planted to macadamia in Australia and the area is growing, as global demand outstrips supply
  • Macadamia is a long-term investment, with orchards taking 7-10 years to reach full production
  • It is an intensive horticultural enterprise that requires many regular operations throughout the year that have to be completed in a timely manner
  • Macadamias can be marketed as in-shell, bulk raw, roasted and/or flavoured kernel, retail packs of kernel (raw or roasted) and value-added product

Production status

The Australian Nut Industry Council estimates that by 2020, 24,000ha will be planted to macadamias and production greater than 18,500t. Export value is set to exceed $280 million.

Macadamias are grown in subtropical and tropical climates, mainly along the seaboard of northern New South Wales and the eastern seaboard of Queensland. The majority of plantings are in the Northern Rivers region of New South Wales (47%) and around Bundaberg in Queensland (32%).

Uses

The nuts of the macadamia are eaten raw or dry roasted, as a snack food or as an ingredient of bakery products, ice cream and confectionary products, and in the restaurant and food service industries.

Indigenous Australians have long-regarded macadamia or ‘kindal kindal’ as a delicacy. When macadamia were first consumed by Europeans they were considered a luxury food due to their delicate taste.

Increasingly, macadamia nuts are recognised for their health benefits. The oil in macadamias is mostly monounsaturated and unsaturated fats, which help maintain ideal cholesterol levels. Macadamias contain amounts of natural plant sterols and arginine, which help to keep blood vessels relaxed and flexible. They contain around two grams of fibre per 30g serve, which is similar to the fibre in a slice of wholemeal bread. Macadamias also contain antioxidants and daily consumption can be considered beneficial for health.

Production Requirements

Growing regions

Macadamias are a subtropical rainforest tree that have evolved in an environment of rich soils, warm temperatures and high rainfall. Naturally they occur at elevations near sea level up to 600m, and prefer well-drained sites on hill crests, hill slopes, scree slopes, foot slopes and along the edges of hoop pine scrubs and creek beds, in generally frost-free environments.

Commercial macadamia production occurs mainly along the eastern seaboard from Nambucca Heads in northern New South Wales through to Mackay in north Queensland. The recognised growing regions (and percentage of national production) are: Northern Rivers NSW (47%), Bundaberg (32%), Gympie (9%), South East Queensland (6%), Mid Coast NSW (5%) and areas outside these main regions (1%). Bundaberg and Emerald in QLD, as well as the Clarence Valley in NSW, are the fastest growing production regions.

Soil type

In the wild, macadamia grows on uniformly dark soils that vary in texture from clayey sand through various types of loam to silty clay.

Under cultivation, macadamias grow on a wide range of soils but perform best on well-drained soils with deep topsoil (1–2m) and high organic matter content (> 4% organic carbon). Ideally the soil should have pH(CaCl2) of 5.0. Heavy clay soils should be avoided, as prolonged periods of waterlogging may result in root diseases and tree death.

Climate

Macadamias are a subtropical rainforest tree and perform best in areas that have distinct wet and dry periods. However they can tolerate a wide range of moisture conditions.

Temperature is a major factor that influences growth and productivity. Optimum growth occurs between 20-25°C but close planting and irrigation can reduce the impact of high temperatures at locations in mid-north and north Queensland.

Mature macadamias can tolerate short periods of frost down to 6°C but young trees can be severely damaged by frost at 1–2°C.

Natural rainfall of 1,200–2,300mm will optimise productivity but in areas receiving less than 1,200mm, irrigation will be required during extended dry periods.

Sites that experience strong winds are not ideal, as macadamias do not have a clearly defined tap root and young trees are particularly prone to blowing over in strong winds.

Terrain is also an important consideration when selecting a site to grow macadamias. Although they will grow on steep hill sides and rocky sites, slopes of 15% or less are preferred to minimise erosion and to allow efficient machinery access.

Varieties

Most of the macadamia trees grown in Australia are selections of good provenance stock or lines that performed well in the first commercial orchards in Hawaii — which were selected from plants grown from seed collected in Australia in 1892. Popular lines include 246, 660, 816 and 849, however 344 is still the most widely planted variety.

Some Australian selections have been made from local wild stock, and propagated for commercial production; these include A4, A16 and A38.

Different lines have different growth habits (spreading or upright), canopy density and fruiting times, therefore suitability for different regions will vary. New growers should consult an advisor or specialist horticultural nursery before purchasing planting stock.

Cross-pollination is important to achieve nut set of macadamias, so at least two cultivars with overlapping flowering times must be planted in one block. Different cultivars should be planted in different rows to avoid transfer of diseases between cultivars, and to avoid harvest and storage problems, if cultivars have different maturity times/patterns. In Australia, the major pollinators in commercial macadamia plantations are the introduced honey bee and native bees of the genus Trigona.

Planting and crop management

The orchard site should be clear of tree stumps, old tree roots and surface rock; and planting rows may require deep ripping to create a friable, well-draining root zone, about 1–2m deep. Soil tests should be conducted to aid correction of soil pH and nutrient levels several months before planting.

Orchards should be established on land with gradients less than 15°C to allow for safe mechanical cultural operations and minimal risk soil erosion. Grassed waterways and shallow drains above and within the orchard should be established to carry torrential rainfall. Long rows within the orchard maximise land use and efficient machinery operation; and north–south row orientation allows sunlight on both sides of the trees, particularly in winter. Tree rows can be gently mounded, leaving a shallow broad based drain to reduce the opportunity of ponding or waterlogging in wet periods.

Tree variety, soil conditions and topography will affect planting distance which can vary from 6x3m to 10x4m. Trees planted at high densities are more costly to establish but will come into production earlier, reducing the time to reach a positive cash flow.

Windbreaks could be considered for exposed sites, and planted 1–3 years before planting the orchard. Australian native species such as casuarinas (Casuarina cunninghamiana) and tallowwood (Eucalyptus microcorys) can be used.

Trees can be planted in autumn or spring, with autumn planting preferred for grafted trees. Generally, one or two hand waterings will be sufficient to establish autumn-planted trees but spring-planted trees will require more waterings or temporary irrigation because of the likelihood of dry spells. In frost-prone areas, it is recommended to wrap the trunks of young trees for protection against light frosts.

Young trees will require small regular applications of fertiliser from September to May, with rates increasing until the trees begin to bear fruit at about six years. The fertiliser program for nut-bearing trees should be based on leaf and soil analysis, nutrient removal and additional nitrogen to sustain tree vigour. Soil should be maintained at pH(CaCl2) 5.0, therefore an application of lime or dolomite may be required every few years (3–5).

If weather conditions are dry during the first year of the orchard, trees will require up to 40 litres of water per tree per week. Once established, use soil moisture monitoring systems, such as tensiometers or capacitance probes, to estimate water requirements effectively and efficiently. Mulching is an important practice to conserve soil moisture.

Trees need to be managed for canopy growth, however, approaches can vary from pruning to no pruning – research is underway to investigate the best approach. Once the tree starts bearing fruit, canopy management will entail: skirting to provide clear ground level access for harvesting, slashing, weed control and fertiliser application, as well as maintain good light penetration of the canopy; and heading to maintain trees at a manageable height, generally about 7m, and to allow light and air to the floor of the orchard.

The publications Macadamia culture in NSW and Macadamia grower’s handbook provide good detail on orchard management.

Weeds, pests, and diseases

Weeds compete vigorously with newly planted trees for water and nutrients, therefore weed control is important when preparing the site for planting, and mulching of the rows after planting. Weeds are generally not a problem in a well-maintained mature macadamia orchard, as the inter-row area is mown regularly to assist access to the trees. As the orchard matures, the trees shade a large area of the ground surface, preventing the establishment of weeds.

Macadamias are susceptible to several pests and diseases, and on detection, control of these is essential to prevent loss of yield and quality. Pest and disease scouts (consultants) are engaged by a large majority of growers to check orchards on a regular basis, and recommend control measures.

A range of insect pests can attack macadamias, and in sufficient numbers will require control measures. Pests include fruit spotting bug, banana spotting-bug, lace bug, macadamia twig girdler, banana fruit caterpillar, macadamia nut borer, thrips, macadamia leaf miner, macadamia feltid coccid, macadamia kernel grub, sigastus weevil, mites, bark beetle and pinhole borer.

Diseases that may affect macadamia trees include phytophora, botrytis, husk spot and scale.

Rats can also be a pest in orchards when nuts have fallen to the ground and await harvest and wild pigs are a problem in and around Gympie and in parts of south east Queensland.

Detailed information on the management of pest and diseases is provided in NSW Macadamia plant protection guide 2016–17

Infrastructure Requirements

The infrastructure and equipment required for a macadamia orchard, as listed in the AMS/Queensland Government’s Macadamia grower’s handbook, are:

  • irrigation system, including a dam, piping and under-tree sprinklers (in some areas)
  • tractor (about 90 HP)
  • 4WD utility
  • trailer
  • slasher
  • fertiliser spreader
  • boomsprayer for herbicides and sprayer for insecticides and fungicides
  • harvester
  • shed for postharvest handling
  • dehusker and sorting equipment
  • silo or similar for drying and storing nuts.

Contract services will be available for most operations, especially harvesting and processing, and may be an option to reduce capital expenditure. However, it is important to be confident that the services will be available at critical times.

Generally, it is expected that one person could manage a macadamia orchard of 30ha (non-irrigated) and 20ha (irrigated) for the first 4–5 years. Once trees begin to bear and up until the eighth year, casual labour may be required for harvest, dehusking and sorting (although most processors now accept nuts in-shell direct from farmers and undertake dehusking, drying and sorting themselves). From the eighth year onwards, harvest will require the purchase of a harvester, contract harvest services or significant hired labour.

Harvesting & Processing

Macadamia trees will start bearing nuts after about 4-5 years but it can take up to 7-10 years for a macadamia tree to reach maturity and maximum yield.

In preparation for harvest, the orchard floor will require cleaning in late summer, by mulching immature early fallen nuts and grass. In south east Queensland, mature nuts will drop in mid-February through to about August and earlier in north and central Queensland. In New South Wales, the nuts fall to the ground between March and September. Generally, nuts are harvested from the ground about every four weeks during these months, using a mechanical harvester that picks up the nuts with finger wheels or sweepers.

For some ‘sticktight’ varieties, treatment with ethephon to promote nut drop may be used.

Most fallen nuts are contained within the fibrous outer husk, which needs to be removed within 24 hours of harvest to prevent deterioration of nut quality. Most processors will take the ‘nut in husk’ and dehusk and dry the nuts. Rocks, sticks and leaves are removed by hand or mechanically, before dehusking. The dehusking machine has mechanical rollers that split the fibrous husk to release the nut-in-shell.

After dehusking, the nut-in-shell is inspected and sorted for damage or defects, and sometimes also water sorted to remove immature nuts, which are not able to be detected by visual sorting.

The dehusked and sorted nut may be dried and sorted on farm, or sent immediately to a processor.

Drying shrinks the kernel away from the inside of the shell, allowing the shells to be cracked without damaging the kernel. Drying involves reducing the moisture content of the nut-in-shell, which can be up to 30% at harvest, down to 10%. If large quantities of nuts are to be handled, forced air drying in silos and bins is required.

After drying, the kernel is extracted from the shell by passing the nuts through a machine with either a fixed blade and cutting blade, or a combination of rollers and a base plate to compress the shell.

Raw macadamias, in airtight packaging, can be stored in cool (ideally below 12°C), dark, dry conditions for up to 24 months.

Detailed information about post-harvest processing is available in the Macadamia grower’s handbook.

Markets & Marketing

Consumer demand for macadamia exceeds supply, across the globe. Increased consumption is attributed to increased interest in healthy foods and increased awareness of the benefits of eating tree nuts. The greatest demand is from Asian markets, where consumers are adopting western-style foods and eating patterns (i.e. snacking and eating on the go).

Generally about 65% of the annual Australian macadamia crop is exported. The major international markets were China, Japan and Europe.

Australia is the world’s largest producer and exporter of macadamia kernel. Macadamias can be marketed as in-shell, bulk raw kernel, retail packs of kernel (raw or roasted) and value-added product.

Growers participate in the marketing process at many different levels. They may simply produce the nuts and sell their product, usually under contract, as dried nut-in-shell to a processor. The processor undertakes the risks and benefits of marketing accumulated product, processed according to contracts. Sometimes, however, the processor is a cooperative of growers, and the grower will benefit from the marketing process, as well as production.

Some growers, small and large, may manage the whole production chain, and process (on farm or under contract), value-add and market their own product, however, of the 35% of Australian macadamia production that is consumed domestically, about 90% is sold as raw kernel and is processed for snack foods or used as an ingredient in confectionery, cereals, ice-cream and bakery products.

New macadamia growers are advised to speak with industry representatives and advisors to determine the best marketing opportunities for their individual situation.

Risks & Regulations

Risks/challenges

The prospects for the macadamia industry are good however a macadamia enterprise is a long-term investment, which brings inherent risks associated with delayed positive cash flows and unforseen market changes. The trees do not come into production until the fourth or fifth year after planting, and full production is not reached until 7-10 years after planting; and equipment is expensive compared with other horticultural crops. The payback period for macadamias is much longer than for some other nut crops.

The market for macadamias is predominantly export so there can be significant variability in pricing from year to year, as affected by currency exchange rates and production in other countries; and long-term markets are subject to trade relationships and political influences, making it difficult to plan future returns. From a production perspective, site selection is critical for success due to the macadamia’s limited tolerance of frost, heat, wind, drought, fire or poorly drained soil.

At the farm level, farm practices have a strong influence on viability. The Macadamia industry benchmark report for seasons 2009 to 2016 aims to support improved productivity and profitability within the Australian macadamia industry. Increased and sustained yields of saleable kernel will lead to the ability of the industry to demand premium prices and encourage greater investment from food manufacturers.

Although published in 2004, the Macadamia grower’s handbook published by the Queensland Government provides excellent detail about considerations for new growers.

The withdrawal of endosulfan from the list of permitted pesticides has limited chemical control options for insects and encouraged infestation of secondary pests such as lace bug, mites, thrips and weevils. With fewer chemical options, and fewer modes of chemical activity, the effectiveness of integrated pest management (IPM) strategies has been reduced, and presents a new challenge for the industry.  However, there are biological controls for a number of pests including Trichogramma wasp for nut borer.

Regulatory considerations

The regulatory considerations that apply to all Australian farms, including laws applying to chemical use and management, occupational health and safety and transport (including machinery movements and the loading/unloading of harvested product), also apply to macadamia farming operations. If nuts are being processed on farm, local government should be consulted to ensure that prospective facilities and operations meet local planning and environmental regulations.

When processing raw product and value-adding, consideration should be given to food standards regulations, as administered by Food Standards Australia New Zealand (FSANZ) and set out in Chapter 3 of its Food Standards Code. Information about certification can be found at, but is not limited to, the websites of Freshcare and HACCP.

Publications

Publications/information

Macadamia industry benchmark report: 2009 to 2016 seasons Queensland Department of Agriculture and Fisheries (2017)

Macadamia grower’s handbook Queensland Government (DEEDI) (2004)

Macadamia plant protection guide 2016-17 NSW DPI Management Guide

Macadamia page on the website of Horticulture Australia

Nut growers guide: the complete handbook for producers and hobbyists (2005). Jennifer Wilkinson, Landlinks Press (CSIRO Publishing) ISBN 0 643 06963 1

Pollination Aware Case Study: Macadamia RIRDC publication (2010)

Other resources

Macadamias directory of resources on Department of Agriculture, Fisheries and Forestry website, Queensland Government

Nuts directory of resources about macadamia and other nut crops, on NSW Department of Primary Industries website

Image Gallery

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Macadamia nuts on tree

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Macadamia nuts