The macadamia nut or ‘bush nut’ is a native to the Whian Whian. It was a rare but treasured bushtucker food used by the Widjabul for thousands of years. The Aboriginals shared this nut with the early timber cutters however it was not officially described and named until 1858.The bush nut is a native understory tree that thrives in our sub tropical conditions and has today been hybridised to grow in full sun. Modern orchards regularly trial new varieties of this long living crop and records show the oldest known macadamia tree to be 120 yrs old. When Harry Baldwin owned Reeveer Park on Fox Rd he felled a large macca tree believed to be over 100 yrs which was still bearing nuts.

Macadamia nut plantation Rosebank

The first person to plant the bush nut was ‘Sudan’ Jim Armstrong from Dorroughby in the 1870’s. The Macadamia Nut Association was formed in 1932 and large scale production commenced in the 1970’s. The Northern Rivers now contributes 20-25% of the world’s production. The industry has also expanded into the organic market to meet this growing trend and uses integrated pest management controls to achieve organic status.

When the macca industry first established in Rosebank, the farmers planted thousands of tallowwood & flooded gums as windbreaks around their crops. Today these gums have now matured and are an aesthetic feature of the area. The eucalypts also became successful widlife corridors for the koalas and gliders and have assisted with integrated pest management. Many properties use these trees to house owl boxes to encourage owls as predators of the feral rodents that invade the plantations.

The Macadamia Nuts of Rosebank

by Doug Rowley (with a little help from Roger Barlow).

Close-up of a healthy bunch
of Macadamia nuts
photo: Roger Barlow

One of the same young trees 5 years
later with its first fruit
photo: Roger Barlow

Piles of compost ready for spreading
photo: Roger Barlow

Non-chemical, biological control — strips of parasitic wasps attached to leaves
photo: Roger Barlow

Doug Rowley’s very smothergrassy Macadamia orchard
photo: Roger Barlow

The Australian Bush Nut

The Macadamia, or Australian Bush Nut, is the major horticultural crop grown in Rosebank. It is a sub-tropical rainforest tree, originally native to the area, and perfectly suited to our climate. The Macadamia nut is the only native product that has been successfully commercialised and is sold within Australia and exported to Europe, Asia and the USA. It is also grown in New Zealand, Hawaii, Brazil, South Africa and Kenya but Australia has been the world’s largest producer since 1998.

From nursery to nut production

Painting the trunks of baby trees just planted out in a Rosebank orchard — to deter wallabies from ring-barking them
photo: Roger Barlow

There are many different varieties but they share similar characteristics and require similar growing techniques. Trees are usually grown from seed, and then at 12 months of age the chosen variety is grafted onto the rootstock. After another 6 to 8 months they are planted out in the orchard with the most common planting grid being 8 metres between rows and 4 metres between individual trees. It can take from 4 to 6 years, depending on the variety, before they start to produce nuts.

Harvesting, dehusking and composting

The trees usually flower twice a season, the first flowering is in the May/June period with the second flowering in August/September. When the nuts are mature they fall off the tree and harvesting off the ground usually starts in March and continues until October. Industry best practice is to pick up the nuts from the ground within 3 to 4 weeks of falling otherwise the quality can start to deteriorate. The nut has a fibrous outer husk that needs to be removed within 1 day of harvest. Some farms have their own dehusking equipment while others send the nuts in husk to processors and have them do the dehusking. The husk is stored to the end of the season; some farms use it to make compost, a process that takes about 3 months. This compost is then spread throughout the orchard. Other growers mix the husk with chicken litter and spread that in their orchards.

Reducing pesticides

Pests and fungus problems occur throughout the nut-growing season and macadamia growers have to control them to minimise crop losses. There are three main pests of which two are controlled by spraying insecticides. For the third pest we have a biological control — a parasitic wasp — that now completely eliminates the need to spray for nutborer. Work is well under way to develop a biological control to control fruit spotting bug and we hope it will be commercially available from 2014. This will leave only one pest to control by spraying.

Looking after the environment

A koala in Roger Barlow’s Rosebank Macadamia orchard
photo: Roger Barlow

Growers are responsible custodians of the land and encourage bio diversity on their farms as this helps control pests and diseases and is good for the environment. They also focus on maintaining good soil health and plant nutrition to help maximise crop yields. As orchards mature they start to canopy over and shade out the groundcover. When we have a big rain event this can mean a loss of topsoil. Growers are becoming increasingly aware of the need to maintain grass cover in orchards and undertake pruning strategies to maintain or increase light penetration onto the orchard floor. Shade-tolerant smothergrass, a vigorously spreading grass, is now used extensively to help prevent soil erosion.

Smothergrass just strip-planted on Roger Barlow’s farm
photo: Roger Barlow

Same smothergrass with temporary millet growing 3 months later (plus very fat wallaby)
photo: Roger Barlow

Want to know more?

The peak body for macadamias is the Australian Macadamia Society Ltd; about 70% of the shareholders are growers while the other 30% comprise processors, consultants, researchers and academics. They have a good website full of interesting information and some great Macadamia recipes. Try it out at or just ask one of our friendly growers who always have time for a chat.